UNIVERSITY OF CALIFORNIA

COLLEGE OF AGRICULTURE

AGRICULTURAL EXPERIMENT STATION

BERKELEY, CALIFORNIA

POLLINATION OF THE
SWEET CHERRY

BY
WARREN P. TUFTS AND GUY L. PHILP

BULLETIN No. 385

March, 1925

UNIVERSITY OF CALIFORNIA PRINTING OFFICE

BERKELEY, CALIFORNIA

1925

POLLINATION OF THE SWEET CHERRY

By WARREN P. TUFTS and GUY L. PHILP

In 1913 Gardner 1 published the results of rather extensive polli-
nation studies with sweet cherries and showed that all varieties tested
are self -sterile under Oregon conditions.

Hedrick, 2 in 1915, stated that sweet cherries as grown in New York
appear to be, for all practical purposes, self-fertile. More recently
Wellington 3 working in the same state, made the following statement :
1 ' Sweet cherries are practically self -sterile, and in fact many varieties
are inter-sterile."

Crane 4 reports that all sweet cherries which have been tested in
England are found to be self -sterile, and that in a number of instances
there appears to be incompatibility between varieties. He also calls
attention to the fact that there appear to be "strains" existing
within certain of the cherry varieties. Hooper, 5 another English
investigator, finds conditions similar to those reported by Crane.

Florin 6 reports that in Sweden numerous Bigarreaus and Hearts
are practically self-sterile and therefore require cross-pollination to
set fruit.

These facts, together with reports of crop failure in many cherry
orchards in different sections of California, indicated the need of
accurate information on this subject and led the writers to conduct
rather extensive experiments during the years 1916, 1917, 1918, 1919,
1920, 1922, 1923, and 1924. The work has yielded some interesting
results, which are presented in this paper. The data secured do not
permit the drawing of final conclusions, so that it is essentially a
progress report.

PROBLEMS OF SWEET CHERRY POLLINATION

In planning the work, the writers had in mind the differences of
altitude, climate, and soil, that exist in various parts of California
and have attempted to answer the following questions for these
various conditions ;

1. Will sweet cherry varieties, when planted in solid blocks, i.e.,
without pollinizers, be commercially profitable? If so, the varieties
may be classed as self -fertile ; if unprofitable, then they should be
classed as self -sterile.*

*The writers prefer the terms lt barren' ' and - 'fruitful' ' as explained by
Kraus in the Journal of Heredity, Vol. 6, No. 12, pp. 549-557, 1915, rather than
the inexact terms "sterile" and "fertile." The latter terms have been used
in this paper because the general public is more familiar with these expressions.

4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

2. If cherry varieties are self -sterile, what varieties may be planted
together to produce profitable crops? This is a question of inter-
fertility.

S-X^NXvGX^t

'"Coo TcLV

^oo^e S^C&cu,

o \w cx'b cuAtcxA^cL

Fig. 1. — Showing the different stages of bloom from a pollination standpoint.
(1) Immature; (2) Too far advanced (several petals removed to show flower
structure); (3) Proper stage for emasculation; (4) Emasculated.

Bulletin 385] pollination of the sweet cherry 5

3. When planting inter-fertile varieties together the following
points should always be considered in selecting the pollinizers:

(a) Coincidence of bloom of pollinizer with that of the variety to
be pollinated.

Fig. 2. — Typical branch for emasculation. Note the large percentage of
blossoms at the proper stage of maturity for emasculation.

6 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

(b) Germinability of pollen produced by the pollinizer.

(d) Commercial value of pollinizer.

(e) Succession of ripening for convenience of harvesting.

ORGANIZATION OF THE WOEK

The methods employed were those commonly used in cross-polli-
nation experiments. The work consisted in first removing the stamens
and then applying the pollen desired (figs. 1 and 2). Exact counts of
the artificially pollinated flowers were made and the fruits resulting
from them counted at harvest.

Experiments were conducted at Davis and Vacaville in 1916-1920,
at Watsonville in 1916, at San Leandro in 1917, at Santa Clara in
1920, in the Occidental district of Sonoma County in 1922 and 1923,
and in Placer County in 1924. In these experiments about 67,000
blossoms were self-pollinated, 300,000 cross-pollinated, and 290,000
counted to determine the normal set.

THE BLOOMING PEEIOD OF CERTAIN CHERRY VARIETIES

Cherries have a comparatively long blooming period if the whole
time from the opening of the first flowers to the shedding of the last
blossoms is considered. The average length of the blooming period
for most varieties is about two weeks. This period may be nearly a
month in certain seasons. Weather conditions during and just pre-
ceding the blooming period have a marked influence upon the length
of the period of bloom and also upon the dates of blooming. Because
of climatic conditions, the dates may vary as much as three or four
weeks in different seasons.

Varieties, however, keep approximately the same order of blooming
each season. From observations in the Vaca Valley for four years,
the following varieties may be divided into early and late bloomers.
They are listed in their order of earliness.

Early Bloomers Late Bloomers

Advance Rockport

Chapman Pontiac

Black Heart Bjng

Early Purple Napoleon

Black Tartarian Lambert

Burbank

Black Republican

Bulletin 385] POLLINATION OF THE SWEET CHERRY

Under most conditions, Black Tartarian and Black Republican
overlap the varieties in the second column enough for cross-polli-
nizing.

The accompanying chart, figure 3, gives the average period of
effective bloom for certain cherry varieties as grown in the Vaca
Valley for the years 1917 to 1920, inclusive. The term effective
bloom is used to designate the length of time the tree is in conspicuous
blossom.

Periopot Effective Blcwi or Certain Cherry Varieties

Vaca VALLLy-CAuroR/iiA 1917 to \320~lncL\JSNt

ycARS

Black Heart 4

Black Tartarian a

Ghapma/s 4

Apva/mch 3

Early Pi/rple a

BvRBA,NK 4

Black Republics a

Pontiac A

Bl/1G 4

/Iapoleon 4

rockport 3

Lambert a

MARCH

APRIL

■/

/ft

Fig. 3. — The period of effective bloom of certain cherry varieties, covering
a period in nearly all cases of four years. The number of years averaged is
shown in a separate column for each variety.

ABUNDANCE AND VIABILITY OF POLLEN

In order to secure the best results under field conditions from cross-
pollination, it is necessary to have varieties which are good pollen
producers. Fortunately, most cherry varieties are satisfactory in this
respect as indicated in table 1.

TABLE 1

Kelative Abundance of Pollen Produced by Different Varieties

Variety

Pollen
Production

Variety-

Pollen
Production

Abundance

Medium

Giant

Abundant

Advance

Medium

Knight

Abundant

Black Heart

Medium to shy

Lambert

Medium to abundant

Black Bepublican

Medium

Major Francis

Abundant

Black Tartarian

Medium to abundant

Schmidt

Abundant

Bing

Medium

Waterloo Heart

Abundant

Burbank

Medium

Windsor

Abundant

Centennial

Shy

Wood

Abundant

Downer

Abundant

Early Purple

Medium to abundant

8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

To determine whether the pollen to be used was viable, each sample
collected was tested in a 12 per cent cane sugar solution. While cherry
pollen is not as viable as the pollen of some other fruits, in most cases
a satisfactory artificial germination was secured. Where possible a
new collection of pollen was made when satisfactory results were not
obtained with the pollen first collected.

There seems to be a close correlation betwen the abundance and
germinability of the pollen and the weather conditions just preceding
and during the blooming period. Warm, clear weather is favorable
to an abundance of pollen of high germinability, while cold, cloudy
weather results in a scant amount of pollen of low germinability.

There is a wide range in the percentage of germination among
different varieties and also in the same variety at different places in
the same and in different seasons. As much as 3 to 88 per cent
variation in the pollen of a single variety was found in differnt
localities during one season.

The writers secured on the average an artificial germination of
about 30 per cent. This was considered satisfactory. In certain
crosses, a 30 to 50 per cent set resulted from using pollen with only
a 3 to 5 per cent artificial germination.

The preceding figures seem to indicate that a low artificial germi-
nation does not necessarily mean that a poor set will result. However,
since so many factors determine the setting of fruit, it seemed advis-
able to avoid the use of pollen of low viability, which might tend
towards further confusion in interpretating the results.

NORMAL SET OF CHERRY VARIETIES

Immediately after the petals fall, each flower begins to form a
fruit. During the following two or three weeks a certain percentage
of these young fruits, for reasons not fully understood, drop off,
leaving only a rather low percentage of the total number of original
blossoms to continue development. It is quite necessary that this
drop take place, as the tree under average circumstances would not
be able to carry so many fruits through to maturity. The exact factors
determining which of these young fruits shall drop are not known at
present. Later in the season still another falling off of the young
fruits occurs. This is known as the ''June drop."

The expression ''normal set" is used to designate the percentage
of fruit which sets under normal conditions when the tree is left open
to insect pollination. The normal set may be determined at any time
up to the end of the season by counting the fruits on a tree and com-

Bulletin 385] pollination of the sweet cherry 9

paring this number with that of the blossoms. In these experiments,
approximately, two thousand blossoms of each variety, well distributed
over the trees, were counted each year and records made of the normal
set after the first drop, after the second drop, and at harvest time.

The normal set is used for comparison of the different crosses. A
study of the normal set in table 3 indicates that most varieties set a
good crop in 1916, 1917, and 1920.

A few varieties failed to give a good crop in these years. Indi-
vidual variations and condition or vigor of the trees may be partly
responsible for the shortage, though all the trees used appeared to be
moderately vigorous and received good commercial care.

The normal set on these same trees during the years 1918 and 1919
was far below the average, mainly because of drought and a heavy
frost during the blooming period in 1918. It was also noted that
there were few bees in the orchard during the blooming period of
these years.

SELF-POLLINATION OF SWEET CHEEEIES

During the years 1916 to 1924, inclusive, the following varieties
of sweet cherries were tested for self -sterility : Abundance, Advance,
Black Bigarreau, Black Heart, Black Republican, Black Tartarian,
Bing, Burbank, Burr Seedling, Chapman, Centennial, Cleveland,
Downer, Early Purple, Lambert, Major Francis, Mezel, Pontiac,
Rockport, Schmidt, Napoleon (Royal Ann) (fig. 4), Waterloo Heart,
Windsor, and Wood. In addition to these a number of promising
seedlings and strains were tested. They were tested for from one to
six years and in no year or locality did any variety give a satisfactory
set of fruit when self -pollinated, as is shown by table 2. The Bing,
during the season of 1917, set a 3.5 per cent crop with its own pollen,
but the same year the normal set was over 20 per cent. From a com-
mercial standpoint, all sweet cherries thus far tested under California
conditions may be considered as self -sterile. It is therefore inadvisable
to plant any of the commercial varieties alone or in solid blocks.

POLLINATION REQUIREMENTS OF CERTAIN CHERRY VARIETIES

The facts presented in table 3 are based on the results obtained
from pollination experiments conducted in the Vaca Valley during the
years 1916 to 1920, inclusive.

The data secured in other experiments conducted at Watsonville,
San Leandro, Santa Clara, Occidental, and Newcastle have been
omitted because they would not in any way alter the conclusions.

UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

The results of certain crosses are difficult to analyze and in some
instances have been discarded in the discussion. This is particularly
true for the year 1918, when a severe frost was largely responsible
for the poor sets obtained.

Fig. 4. — Napoleon X Self. No fruit set on a branch of Napoleon which was
pollinated with its own pollen. A typical case of Napoleon when self-pollinated.

Bulletin 385] POLLINATION OF THE SWEET CHERRY

TABLE 2
Self-Pollination. Summary for All Locations

1916

1917

1918

1919

1920

1922

1924

Varieties

co
co

— CO
<n

6 »

-to

-to
C
tt

Xi cu

6 3

CD
CO

-to

a
cu
o

CO
CO

■3*3

— CD
CO

d 3

-to
<D
CO

-to
CI
O

CD
ft

CO
CO

X! CD
CO

O 3

-to
O
co

-to

o
cu

CO
CO

■§*

6 3

-to
CU
CO

-to
CI
V
CJ

t-l
cu
ft

CO
CO

d 3

-to

CO
-to

CO
CO

-Q cu

d 3

-to

CO
-to

429

Advance ..

2039
1053

0.0
3.5

2159
665

0.5
0.1

970

288

0.1
0.3

762
1168

410

286
1395
1827

368

0.7
0.5
0.9
2.0
0.5
0.9
1.6

Bing

533

0.2

986

0.0

Black Heart

883
2536
5060

0.0
0.3
0.0

432

872

2142

502

0.2

0.1
0.0
0.0

603

519

1056

432

0.0

0.0
0.0
0.0

Black Republican

1288
1647

0.0
0.0

429
1181

1.4
0.2

Black Tartarian

Burbank

Burr Seedling

1015

0.0

645

0.2

Chapman..

1104

0.1

513

0.0

434

1.3

Cleveland

1092

0.8

Downer....

304

Early Purple...

1088
1044

1.0
1.2

504
400

0.4
0.0

214
493

0.9

0.0

390
1056

2.3

0.3

Lambert

1010

0.5

L. S. Royal Ann

722

1.0

388

Mezel

1392

3627

1024

586

0.0
1.0
0.1
0.3

Napoleon

2233

0.0

522
429
509

0.0

0.0
1.3

500
440

472

0.0
0.0
0.0

1547
534
474

0.7
0.0
0.6

2952

0.4

Pontiac

Rockport

404

0.7

Schmidt

448
321
362
404

n o

Windsor

Wood

610

0.0

The value of different pollinizers for each variety as appears from
the results shown in table 3 is as follows :

Advance. — Black Tartarian is the best pollinizer for Advance.
Black Heart, Early Purple, and Chapman are fairly satisfactory.
Advance and Rockport are inter-sterile.

Bing. — Napoleon and Lambert are inter-sterile with Bing". Black
Tartarian, Early Purple, Pontiac, and Black Republican are satis-
factory as pollinizers for Bing and are recommended in the order
named. Figure 5 shows graphically the pollination requirements of
the Bing.

Black Heart. — Black Tartarian, Early Purple, Burbank, and Chap-
man are recommended as pollinizers for the Black Heart in the order
mentioned.

UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

TABLE 3

Cross -Pollination — Interior Valley. University Farm and Vaca Valley

1916

1917

1918

1919

1920

Varieties

No.
blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per
cent
set

No.

blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per
cent
set

Advance {Vaca Valley)*:

Normal Set

5671
2039
1018

29.3
0.0
3.8

2302

1093

499

11.2
0.1
0.4

2344
515
392
242
457
519
748
369
365

1778
455

7.0
0.2
6.0
0.0
8.0
3.0
10.5
5.4
0.0

10.0
0.0

2321
456
494

14.6

xSelf

0.0

x Black Heart (Vaca Valley)

21.0

x Black Republican (Alamo)

x Black Tartarian (Watson)

289

15.9

481
514
535
564
390

2650

1066

550

576

0.0
0.0
0.0
0.0
0.0

9.7
0.0
8.3
4.6

480
517
732
522
493

2510
306
412
447
548
559
552

24.0

x Burbank (Vaca Valley)

3.4

x Chapman (Alamo)

1029
1047

5.4

4.5

8.4

x Early Purple (Watson)

20.0

x Rockport (Payne)

0.0

Advance (Watson):

Normal Set

34.0

xSelf

1.7

x Black Heart (Vaca Valley)

16.2

x Black Tartarian (Watson)

337
269
292
874
366
358

6512

288

0.9
2.0
0.4
2.2
0.2
0.0

4.0
0.3

19.0

x Burbank (Vaca Valley)

1.6

x Chapman (Alamo)

495
601

10.3
0.2

0.7

x Early Purple (Watson)

6.8

x Pontiac (Watson)

x Rockport (Payne)

258

2508
394
373
308
456
264

415
377
304
436

0.0

12.1
0.0
0.5
1.9
0.6
4.1

48.1
3.7
0.0

24.7

443

2609
518

0.5

Bing {Vaca Valley):

Normal Set

1787
533

7.9
0.0

2464
1052

20.6
3.5

35.5

xSelf

0.3

x Black Republican (Alamo)....

x Black Republican (Vaca Valley)..

970
694

24.8
15.0

508
494
528

545
514
534
470

35.0

x Black Tartarian (Alamo)

522
513

39.1
58.3

204
169

125

188
222

0.0
36.7

36.0

15.0

0.0

28.0

x Black Tartarian (Bassford)

57.0

x Black Tartarian (University
Farm)

55.0

x Black Tartarian (Payne)

510

15.9

40.0

x Black Tartarian (Watson)

45.0

x Early Purple (Watson)...

52.7

x Lambert (Vaca Valley) .

701
211
516

0.1

28.4
0.0

452
495

0.7
29.3

x Mezel (Vaca Valley)

x Napoleon (Vaca Valley)

352
575
507

2524
286

0.3

x Pontiac (Watson)....

497

55.2

416
433

2662
432
533
407
537
422
531
234
263
412

40.3
0.7

15.8
0.2
3.9

11.5
5.2
8.5
2.4
2.9
0.3
3.6

263
264

1295
603

44.8
0.4

1.7
0.0

43.0

x Rockport (Payne)

18.5

Black Heart (Vaca Valley):

Normal Set

2243
833

1024
191

22.8

0.0

21.8

37.8

39.0

x Self

2.0

x Advance (Watson)

x Black Tartarian (Alamo)

432

38.0

327
320
319
328
306

46.0

x Black Tartarian (Watson)...

36.0

x Burbank (Vaca Valley)....

50.5

x Chapman (Alamo)

551
514

11.9
22.4

404
343

14.3
39.0

35.0

x Early Purple (Watson)

42.0

x Pontiac (Watson)

x Rockport (Payne)

* Names in parentheses indicate location of tree or source of pollen, i. e., Vaca Valley orchard,
Watson orchard, Alamo orchard, Bassford orchard, Payne orchard and the University Farm orchard.
The latter is at Davis; all the others in the Vaca Valley in Solano County.

Bulletin 385] pollination of the sweet cheery

TABLE 3— (Continued)
Cross-Pollination — Interior Valley. University Farm and Vaca Valley

1916

1917

1918

1919

1920

Varieties

No.
blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per

cent
set

No.

blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per

cent
set

Black Republican (Vaca Valley):

Normal Set

1281
899

22.5

0.0

2046
505

32.3
0.0

2581
400
433

17.2

0.2

59.5

1323
519

12.0
0.0

2359
527
583
380

30.3

xSelf

0.7

x Bing (Vaca Valley)

1.0

x Black Tartarian (Alamo)

750

38.6

611

9.8

50.0

x Black Tartarian (Bassford)

509
325
517

72.7

20.6

0.4

452

50.2

x Black Tartarian (Payne)

x Black Tartarian (Watson)

x Cleveland

170

21.8

x Early Purple (Watson)

426
739

35.4
35.0

569
330

7.7
0.9

514
389

29.5

x Lambert (Vaca Valley)

430
208

17.4
11.5

54.0

x Mezel (Vaca Valley)

x Napoleon (University Farm)

405
314
409

2572
592
521

37.7
16.2
31.7

20.8
0.0
0.7

x Napoleon (Vaca Valley)

405
394

32.1
4.0

465
530

2059
521
533

10.3
10.4

7.8
1.7
2.0

334

377

2570
457
511

28.0

x Rockport (Payne)

30.0

Black Tartarian (Alamo):

Normal Set

2832
1030
977
526
540
503
507

23.1
0.0
7.9

20.3
0.0
0.0

12.8

31.5

xSelf

3.7

x Advance (Vaca Valley)

15.6

x Bing (Vaca Valley)...

x Black Tartarian (Bassford)

502

0.8

x Black Tartarian (Payne)...

x Black Heart (Vaca Valley) ...

495
541
522
522

0.2

10.9

0.2

9.3

548
510
545
594

0.9

8.0

10.0

13.4

313

458
492

588

11.5

x Burbank (Vaca Valley)

13.3

x Chapman (Alamo)

544
539
507

15.6

8.5
0.0

7.5

x Early Purple (Watson)

9.6

x Mezel (Vaca Valley)...

x Rockport (Payne)

458

3200
510
500
503

10.4

1.4
0.0
1.0

4.7

556

3150
535
531
537
516
531
490
523

4.0

2.5
0.0
4.5
4.4
0.0
5.2
2.8
7.2

398

3060
970
458
483

6.0

Black Tartarian (Watson):

Normal Set

14.3

x Self

0.0

x Advance (Vaca Valley)

9.3

x Black Heart (Vaca Valley) ..

3.5

x Black Tartarian (Alamo)...

x Burbank (Vaca Valley)....

329
518
499
544
503

0.0
6.9
0.0
0.5
0.8

529
535
300

528
497

4.7

x Chapman (Alamo)

13.0

x Early Purple (Watson)

2.3

x Pontiac (Watson)

12.0

x Rockport (Payne)

513

3.3

12.0

Black Tartarian (Bassford):
Normal Set

1752
1003
506
522
423
501
509
533
527
333
671
518

30.2
0.0

25.5

14.0
5.2
7.6
0.2
0.0

25.4
6.6
0.0

15.8

xSelf

x Advance (Vaca Valley)

x Bing (Vaca Valley)

x Black Republican (Vaca Valley)

x Black Republican (Watson)

x Black Tartarian (Alamo)

x Black Tartarian (Payne)...

x Chapman (Alamo)

x Lambert (Vaca Valley)

x Mezel (Vaca Valley) .

x Pontiac (Payne)

UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

TABLE 3— (Continued)
Cross -Pollination — Interior Valley. University Farm and Vaca Valley

1916

1917

1918

1919

1920

Varieties

No.
blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per

cent
set

Black Tartarian (Payne):

Normal Set

3541
1058
520
494
502
552
510
632

18.1
0.0

11.5
7.1
2.6
0.0

22.5
1.7

x Self

x Advance (Vaca Valley)

x Bing (Vaca Valley)

x Black Tartarian (Alamo)

x Black Tartarian (Bass)

x Chapman (Alamo)

x Mezel (Vaca Valley)

Burbank (Vaca Valley):

Normal Set

2679
502
522
493
501
476
515

15.1
0.0
2.8
1.4
1.0
0.8
2.3

1517
432
512

9.8

0.0

10.0

1792
368
375

48.4

x Self

1.6

x Advance (Vaca Valley)

12.0

x Bing (Vaca Valley)

x Black Heart (Vaca Valley)

381
501
509

13.6

9.3

23.5

378
345
410

20.4

x Black Republican (Vaca Valley)..

34.8

x Black Tartarian (Alamo)

20.7

x Black Tartarian (Payne)

394

19.8

x Chapman (Alamo)

533
505

388

2617
513
517
523

0.0
4.1
0.0

10.0
0.0
7.3
7.6

440
527
421

2090
504
502
412
462
506
436
462
393

1857
214
346
123
70
410
423
414
504
388
403

3749
493

15.7
6.6
6.6

8.5

0.0

41.4

32.0

1.5

42.0

27.7

2.8

2.5

2.9
0.9
12.4
17.8
5.4
1.0
5.4
0.4
0.0
0.0
0.0

12.0
0.0

399
405
547

2578
334
425
180
588
580
580
605
461

2674
390
420
382

33.0

x Early Purple (Watson)

9.8

x Rockport (Payne)

5.6

Chapman (Alamo):

Normal Set

2330

1104

1019

525

16.4

0.1

10.9

13.9

42.0

x Self

1.3

x Advance (Watson)

17.0

x Black Heart (Vaca Valley)

44.0

x Black Republican (Vaca Valley)..

17.0

x Black Tartarian (Watson)

236

35.6

521
162
389
431

2180
504
631
511
524

6.9
1.2
2.3
0.4

8.4
0.4
0.0
0.0
7.4

43.0

x Burbank (Vaca Valley)

11.0

x Early Purple (Watson)

496

12.5

0.2

x Rockport (Payne)

6.0

Early Purple ( Watson) :

Normal Set

2641

1088

483

527

29.1
1.0
0.5
4.2

26.0

x Self

2.3

x Advance (Watson)

0.0

x Black Heart (Vaca Valley)

1.5

x Black Republican (Alamo)

x Black Tartarian (Alamo)

350

14.9

382
369
380
398
487
419

1837
556

6.5

x Black Tartarian (Watson)

531
489
525

0.0
1.6
0.0

1.6

x Burbank (Vaca Valley)

5.8

x Chapman (Watson)

513

6.6

1.8

x Pontiac (Watson)

9.2

x Rockport (Payne)

495

2505
400

0.0

8.5
0.0

0.0

Lambert (Vaca Valley):

Normal Set

1810
1010

24.4
0.5

2594
1044
450
528
515
501

17.0
1.2
0.2
6.8

32.1
5.8

22.0

x Self

0.5

x Bing (Vaca Valley) ..

x Black Tartarian (Alamo)...

515

22.0

x Black Tartarian (Bassford) ..

x Black Tartarian (Payne) .

x Black Tartarian (University
Farm)

537

11.5

608

18.7

Bulletin 385] POLLINATION OF THE SWEET CHERRY

TAGLE 3— (Concluded)
Cross-Pollination — Interior Valley. University Farm and Vaca Valley

1916

1917

1918

1919

1920

Varieties

No.
blos-
soms
used

Per
cent
set

No.
blos-
soms
used

Per

cent

set

No.
blos-
soms
used

Per

cent
set

No.
blos-
soms
used

Per

cent

set

No.
blos-
soms
used

Per

cent
set

Lambert (Vaca Valley) — Con.

x Black Republican (Vaca Valley)..

398

4.5

525

40.9

516

18.0

x Mezel (Vaca Valley)

500

509

14.4

1.4

22.4

x Napoleon (Vaca Valley)

556
461
502

2048
506
506
496
504
484
452
453

494
543

482

0.5

x Pontiac (Watson)

537
518

3035
522

3.5

2.1

5.9
0.0

534
589

3176
500
507
494
564
508
527
450

497
577
466

44.5

2.7

4.5
0.0
0.0
0.4
0.5
2.7
35.4
7.5

29.9
1.0
0.2

9.3

x Rockport (Payne)

11.0

Napoleon {Vaca Valley):

Normal Set

4251
995
864
973

1737

7.0
0.0
0.0
6.0
0.0

2699
1046
575
564
481
564
540
480

520

15.1
0.2
0.0

21.5
8.7

12.4

30.2
2.9

44.8

24.6

xSelf

0.4

x Bing (Vaca Valley)...

0.5

x Black Republican (Vaca Valley).,
x Black Republican (Watson)

506
546
529
569
519

531
494
560

1.7
0.9
3.7
10.5
1.9

2.4
0.2
0.0

31.0
1.4

x Black Tartarian (Alamo)

31.0

x Black Tartarian (Bassford)

13.0

x Black Tartarian (Payne)

27.0

x Black Tartarian (University

Farm)

26.0

x Black Tartarian (Watson)

16.0

x Lambert (Vaca Valley)

1251
419

0.0
0.0

799
491
519

0.6

24.7
31.4

3.2

x Mezel (Vaca Valley)

x Pontiac (Watson)

550
509

2859
429

3.2
1.9

2.4
0.0

474
586

2200
440
476
372
529
548
406
466

2119
472
507

12.0
0.0

10.0
0.0
25.4
10.7
10.7
3.0
22.0
17.8

3.8
0.0
0.0

521
492

2538
534

12.0

x Rockport (Payne)...

165

0.6

6.3

Pontiac (Watson):

1758
519

6.6
0.2

13.0

x Self

0.0

x Bing (Vaca Valley)

520

1.7

408
411
523
139
414

3077
509
511

6.1
3.8
0.9
0.7
13.5

6.2
1.3
0.0

428
432
465

8.8

x Black Republican (Vaca Valley)..

17.8

x Black Tartarian (Watson) ....

7.7

x Lambert (Vaca Valley)

505
196

11.3
2.6

x Napoleon (Vaca Valley)

185

3282
474
496

0.7

Rockport (Payne):

11.0

xSelf

0.6

2.4

x Bing (Vaca Valley) ..

520

1.7

452
563
530
519
539
504

5.5
16.5

1.3
38.7

6.8
14.6

492
507
504
440
488
555

5.7

9.0
1.0
11.3
0.2
1.5

x Black Republican (Vaca Valley)

460
490
518

7.6

x Black Tartarian (Watson)...

1.2

2.1

x Chapman (Alamo)

x Early Purple (Watson)

614

0.5

x Lambert (Vaca Valley)

505
196

11.3
2.6

x Napoleon (Vaca Valley)

497
562

4.0

24.9

411
159

3.6
5.6

510
434

0.8

x Pontiac (Watson)

0.7

Black Republican. — The following varieties are recommended as
pollinizers for the Black Republican: Black Tartarian, Bing, Early
Purple, Lambert, and Napoleon. Figure 6 shows graphically the
pollination requirements of the Black Republican.

UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

b\m CHERRY POLLINATION

VACAVALLEy-GALir-OR/iiA I9/6toI920 I^clvsivc

Cross

Percent of Blossoms Maturing

1916 1917 1918 J9I9 (920

> IO 20 30 40 SO O !0 20 30 '70 $> O /O 10 30 43 JO O /O £0 30 -M 50 O /£> & 5Q 40 SO

/Formal Set

x5elf

xBlack Republican

xBl ACK TaRTARIA/H

xCaplv Purple

xLambert

x/Sapoleovm

xPo/ITIAG

■

Fig. 5. — This chart shows the influence during the seasons of 1916 to 1920,
inclusive, of various kinds of pollen when applied to the flowers of the Bing
variety. Note the failure to set fruit when self -pollinated; also the inability
of the Napoleon and Lambert pollen to set fruit on the Bing.

Black Tartarian. — Chapman, Advance, Bing", Pontiac, and Early
Purple are recommended as pollinizers for Black Tartarian in the
order named.

BLACK REPVBLICA^N CHERRY POLLINATIONS

Vaca Valley- California 1916 to 1920 Inclusive

Cro55

Percent of Blossoms Maturing

AlORMAL SET

x5e L P

xBlagk Tartarian

xBing

xEarly Pl/rple

xLambert

X>NaPOLEO,M
xRoGKPORT

19)6

3 tO JO so *0 SO

1317 1918 1919

1920

> t° *0 90 *0 JO

^^ m

■

™

■

__._ —

Fig. 6. — This chart shows the influence during the seasons of 1916 to 1920,
inclusive, of various kinds of pollen when applied to the flowers of the Black
Republican variety. Note the failure to set fruit when self-pollinated.

BULLETIN 385] POLLINATION OF THE SWEET CHERRY

Burbank. — Chapman, Black Tartarian, Black Republican, and
Black Heart are satisfactory as pollinizers for the Burbank and are
listed in the order recommended.

Chapman. — Advance, Black Tartarian, and Black Heart are satis-
factory pollinizers for Chapman.

Early Purple. — No satisfactory pollinizer has been found for Early
Purple. Rockport is inter-sterile with Early Purple.

Lambert. — Black Tartarian, Black Republican, and Pontiac are
recommended as pollinizers for Lambert. Napoleon and Bing are
inter-sterile with Lambert.

/NAPOLE07N CHERRY POLLINATIONS

VAGAVALLty-CrtLir-OR/NIA-J9l6T0l920 /AICLV/5IVE

Cross

Percenl of Blossoms Malvring

/SormalSqt

XSCLP
xBl/16

xBlack Repvslican
xBlack Tartarian
xLambcrt

XPo/ITIAC

1316

19 ZO SO 40 $e

■

1317

» O 10 SO 40 iO

■

1318

> /0 10 JO 4Q & t

■

1913

> /a zo jo -jo so .

■

1920

? 'O iO JO 40 JO

■

NMH

^■■■^

BZB

Fig. 7. — This chart shows the influence during the seasons of 1916 to 1920,
inclusive, of various kinds of pollen when applied to the flowers of the
Napoleon variety. Note the failure to set fruit when self -pollinated; also the
inability of the Bing and Lambert pollen to set fruit on the Napoleon.

Napoleon. — Black Tartarian, Black Republican, and Pontiac are
the most satisfactory pollinizers for Napoleon. Bing and Lambert are
inter-sterile with Napoleon. Figure 7 shows graphically the polli-
nation requirements of the Napoleon.

Pontiac. — Advance, Black "Republican, Lambert, and Napoleon
appear to be the best pollinizers for Pontiac.

Rockport. — Burbank, Black Republican, and Pontiac appear to be
the best pollinizers for the Rockport.

The following diagram (fig. 8) represents graphically the varietal
requirements of certain sweet cherry varieties. A square indicates
crosses which are inter-fertile. A circle indicates self -sterility, or inter-
sterility between varieties, and the blank spaces indicate crosses which
are not recommended or which have not been made.

UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

Piagramatig Representation

or- THE
POLLI/NATIO/H REQIREWE/NT5

GERTAW 5WEET CliERRy VARIETIE5

2; <
h y s * z:
c 3 S ? J

-^ cr h k $

_^ -"" -J > ^
i CQ cQ[Q tfl Q

-J
IX

a
C

s >-

iU <*

_] c

O ^ Cl

cx t- s:
<Z K <£

^ r? c£

Apvaace
B1/N6

Bl. )1eart
BlRepvblic/vi
^ DlTartaria/n

^ Bv/R5A/NK

^ Chapman

EarlyPv/rpll-

Laoobert

/Iapoleo/n

Po/NTIAG
<p RoCKPORT

•

■

•

■

•

• I

■

•

■

•

■

•

■

•

■

•

■

•

"•

■

•

■

•

Note : Circ/es Indicate Sterility

Sauares indicate Inter- Fertility

Fig. 8. — This chart indicates the pollination requirements of certain sweet
cherry varieties. The circles indicate sterility, the squares indicate inter-
fertility and the blank spaces, crosses which are not recommended or which
have not been made.

INTER-STERILITY BETWEEN CHERRY VARIETIES

One of the unfortunate conditions existing among cherry varieties
is the inter-sterility of Napoleon, Lambert, and Bing (fig. 9). It is
particularly unfortunate with Napoleon and Bing, since Napoleon is
the important canning variety and also an important shipper, while
Bing is one of the best shipping varieties. Under all California con-
ditions tested these three varieties will not cross-pollinate each other ;
i.e., mixed plantings of them will not produce fruit unless the trees
are within range of some other variety or varieties that are inter-
fertile with them. Gardner 1 and Schuster 7 have observed the same
condition existing in Oregon.

Bulletin 385] pollination of the sweet cherry

vJi

Fig. 9. — Napoleon X Bing. No fruit set on a branch of Napoleon which was
pollinated with Bing pollen. A typical case resulting from crossing Napoleon
with Bing.

Several unimportant varieties have also proved to be inter-sterile
as follows: Advance and Rockport; Early Purple and Rockport.

UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

STEAINS AND VARIETIES

It has been observed that various orchards which consist appar-
ently of the same varieties differ in the size of crop produced. This
fact led the writers to try different trees of the same variety as polli-
nizers in certain crosses. The "sets" obtained, as indicated in table 3,

Fig. 10. — Napoleon X Black Tartarian. One Napoleon fruit set from thirty-
six blossoms pollinated with Black Tartarian pollen. A typical cluster resulting
from crossing Napoleon with a "poor strain" of Black Tartarian.

Bulletin 385] pollination of the sweet cherry

varied so greatly that it was felt that in many instances several
"strains" have been included under one varietal name which more
properly should be used to designate a general type, e.g., the Napoleon
type, the Black Tartarian type, etc.

Practically all early, rather soft black sweet cherries are called
Black Tartarian. In the Vaca Valley alone, the writers have located

Fig. 11. — Napoleon X Black Tartarian. Sixty-two fruit set from one hundred
blossoms pollinated with Black Tartarian pollen. A typical cluster of Napoleon
resulting from crossing Napoleon with a "good strain" of Black Tartarian.

22 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION

five different strains of Black Tartarian which, the same season on the
same Napoleon tree, set from less than 3 per cent (entirely unsatis-
factory) to 40 per cent of fruit with artificial pollination. See
figures 10 and 11.

In the case of Black Republican, under the same conditions noted
above, two strains have been observed.

The majority of the Napoleon trees in various orchards appear to
be true to variety. However, everyone familiar with this so-called
variety has observed considerable variation in the time of bloom and
of ripening, and in the characters of fruit of different trees. The
writers are of the opinion that the Napoleon should be considered a
"type" rather than a true variety.

This condition is not peculiar to California cherry orchards but
seems to be general in the Pacific Coast states. Professor C. E.
Schuster* of Oregon Agricultural College says : ' * I have come to the
conclusion that here is no definite variety in many cases with our
sweet cherries, but rather a 'type.' Professor Gardner's work 1 was
followed in many cases with interest by the growers in this state, and
in several instances his recommendations were followed in planting
out orchards. Within the last year or two, I have visited several of
those orchards that followed his recommendations as to varieties to
use for pollination work and those orchards are getting practically no
results today. The one variety that has given us more trouble than all
others put together, without question, is the Long Stem Waterhouse.
As soon as that variety was recommended for pollination purposes,
anything that had a long stem to it, qualified as a Long Stem Water-
house. ' '

The above quotation indicates that the results obtained in Oregon
are similar to those secured in California. In a recent report Crane 4
of England writes as follows: "Confusion was found in the nomen-
clature of cherry varieties, i.e., three distinct strains of Black Tar-
tarian have already been discovered. ' '

For most cherry varieties there are fairly satisfactory pollinizers.
It should be remembered that there are "strains" and "types" of
cherries. While the writers feel that in many instances the recom-
mended crosses will set satisfactory crops there perhaps will be cases
where growers may unfortunately secure incompatible "strains" or
"types." The data presented in table 3 clearly show that the pollen
of one variety used to pollinate another variety in the same orchard
will not necessarily pollinate what is called the same variety in other

Correspondence with the authors, 1923.

Bulletin 385] pollination of the sweet cherry 23

orchards. The only safe way to know whether two varieties will cross
pollinate is actually to test them. If these varieties are satisfactory
and a grower desires to plant them, he should propagate from scion
wood secured from trees of these respective varieties, the fruitfulness
of which is definitely known. Orchard observation is not always a
safe guide. One instance called to the writers' attention in the
Occidental district of Sonoma County will show the difficulty of
depending altogether on orchard observation. A certain orchard,
supposedly of Napoleons and Bings, had been yielding such good
crops that the neighboring orchardists took it for granted that the
Bings were pollinating the Napoleons. Several of them secured Bing
scion wood to top-work into their own Napoleon orchards for polli-
nation purposes. It was later discovered that there was scattered
through the orchard in question another variety, very similar to the
Napoleon, which one season's experimental work showed to be a
pollinizer of not only the Napoleon but also the Bing. This variety
has been locally called a Long Stem Royal Ann.

POLLINIZING AGENCIES

After having planted inter-fertile varieties, the orchardist should
by all means provide an agency for the transfer of the pollen from the
trees of one variety to those of another. Since the common honey bee
is by far the best carrier of pollen, it will pay the grower to keep
bees, although he may not care to go into the honey business. Bees,
however, are a very profitable side line for the orchardist, especially
if alfalfa fields are available after the blooming season of fruit has
passed. About one hive of bees to an acre of bearing orchard should
be provided. Preferably the hives should be scattered as widely as
possible throughout the orchard during the blooming season. Experi-
ments and experience have shown that little reliance can be placed on
the efficacy of wind and insects, or agencies other than the honey bee,
in effecting the transfer of pollen from tree to tree, or, indeed, from
flower to flower.

Eliminating from consideration all conditions which may influence
the fruitfulness of an orchard except those occurring at blooming time,
it may be said that the set is largely influenced by weather conditions.
Cold weather, besides killing the blossoms or lowering the vitality of
the pollen, often prevents bees from working. The same is true if
cloudy, wet or windy weather prevails. For their best work bees
demand clear, warm, and quiet days, and since the weather at the

24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

time cherries bloom is often very unsettled, it is readily seen that the
blooming' period of the various pollinizing varieties should overlap
perhaps a week, in order that there may be one or two days at least
when the weather will be favorable for insect activity.

It is rather interesting" to note that insects, bees in particular,
are responsible for the pollen transfer in all cases, for such fruits as
the pear, almond, and cherry. In these fruits, no wind pollination
takes place.

The writers have tested the question of wind pollination quite
thoroughly. In the emasculation of cherry blossoms, it has been
found that the stamens are most easily removed by cutting through
the calyx and removing it with the stamens and petals attached. No
flowers emasculated as described above will set fruit unless artificially
pollinated. In other words, the insects will not visit flowers from
which the petals have been removed, nor is pollen blown on the stigmas
by wind, as is shown by the following figures. The following sets
may be compared with the normal sets in table 3 as a check.

In 1920, 6445 emasculated cherry blossoms from nine different
varieties in five different orchards set 27 fruits, a set of 0.4 per cent.

In 1922, 4598 emasculated cherry blossoms from five different
varieties in six different orchards set 1 fruit, a set of 0.02 per cent.

In 1922, 1221 Napoleon blossoms from three different orchards set
1 fruit, a set of 0.08 per cent.

In 1924, 3513 emasculated cherry blossoms from four different
varieties set 20 fruits, a set of 0.5 per cent.

AEEANGEMENT OF THE OECHAED FEOM A POLLINATION

STANDPOINT

In planting- an orchard it is desirable to have at least every sixth
and preferably every fourth row of a pollinizing variety. For con-
venience in harvesting, it is best to plant two rows of one kind, then
two rows of the pollinizing variety, and so on ; or if it is desired to
have more of one variety than another, four rows of the favored
variety and then two rows of the pollinizer, and repeat. For various
reasons, it is often desirable to reduce the number of pollinizing trees
to the minimum. Under these circumstances, one tree in eight is
strongly recommended.

In planting one tree of the pollinizer to seven or eight of the main
variety, the pollinizer should be placed as every third tree in every
third row, as shown in the diagram below, the ''0" in each case
representing a pollinizer tree :

BULLETIN 385] POLLINATION OF THE SWEET CHERRY

On account of the seriousness of the pollination problem with sweet
cherries, it is felt that under certain conditions it may be advisable
to graft over a branch on each tree to a pollinizer. It is realized that
this would tend toward confusion in harvesting ; however, the problem
is so serious that the grower could well afford to forget the commercial
value of the fruit on the pollinizing branch.

The above suggestion is made primarily for the orchardist who
has mature trees which, because of the planting of solid blocks of one
variety or inter-sterile varieties, have failed to produce fruit. Some
relief may be obtained during the years while waiting for the trees
grafted over to pollinizing varieties to come into bearing, by cutting
off branches of pollinizing varieties, placing the cut ends in vessels
of water and distributing them throughout the orchard during the
blooming period. Such limbs will live for several days and continue
to bloom, forming pollen for the bees to transfer to the sterile variety.

SUMMAEY OF CHERRY POLLINATION

1. Sweet cherry varieties may be roughly divided into two classes,
early bloomers and late bloomers, when the period of their effective
bloom is considered.

2. All sweet cherry varieties tested produce satisfactory amounts
of pollen and under most conditions have a satisfactory artificial
germination in a 12 per cent sugar solution.

3. All sweet cherry varieties thus far tested have proved self-
sterile, including Abundance, Advance, Black Bigarreau, Black Heart,
Black Republican, Black Tartarian, Bing, Bur bank, Burr Seedling,
Chapman, Centennial, Cleveland, Downer, Early Purple, Lambert,
Long Stem Royal Ann, Major Francis, Mezel, Napoleon (Royal Ann),
Pontiac, Rockport, and Wood.

4. Napoleon, Lambert and Bing are inter-sterile. Advance and
Rockport are inter-sterile. Early Purple and Rockport are inter-
sterile.

26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

5. Results indicate that many so-called varieties of cherries are in
fact types. This is especially true from a pollination standpoint.

6. It will be necessary to isolate inter-fertile ' ' strains ' ' of the more
important kinds of cherries and propagate from these before uni-
formly high yielding orchards can be secured.

7. Pollinizing agencies, such as honey bees, are necessary to set a
good fruit crop.

8. At least one stand of bees should be provided for each acre of
orchard.

9. Care should be taken in the arrangement of varieties in the
orchard to facilitate cross-pollination and convenience in orchard
management.

10. Solid blocks of inter-sterile varieties may be made fruitful by
grafting in pollinizers.

11. Large limbs of a pollinizer placed in vessels of water and dis-
tributed through the orchard during the blooming period will secure
a set of fruit while inter-fertile grafts are coming into bearing.

RECOMMENDATIONS

Probably the safest way to obtain a high producing sweet cherry
orchard at the present time is to plant a seedling orchard (Mazzard
or Mahaleb), and later top-work the branches with scions taken from
desirable strains.

While the seedling trees are growing, the orchardist should visit
high yielding plantings during the harvesting season and study the
varieties. It will be necessary for him to determine definitely whether
the varieties in which he is interested are cross-pollinating each other
and not being pollinized by chance seedlings or unimportant com-
mercial varieties scattered throughout the orchard under observation.

The work herein reported indicates that a number of so-called
' ' varieties ' ' are not true varieties but rather ' ' types ' ' consisting of a
number of ' ' strains, ' ' some of which are good pollinizers while others
are not. ' I

The only way to learn definitely whether two so-called ' ' varieties ' '
will cross-pollinate is by careful observation, as indicated above, or by
artificial cross-pollination experiments. The writers hope to continue
these experiments with the view of finding particular strains of com-
mercial varieties which are inter-fertile and from which it will be
possible to obtain quantities of scion wood for future plantings.

Bulletin 385] pollination of the sweet cherry 27

An added advantage of top -working is the elimination of serious
bacterial gummosis (Bacterium cerasi Griffin) infections on the trunk
and framework branches. The Mazzard seedling is very resistant to
gummosis. Barss 8 states: "Mahaleb seedlings appear to be immune."
Howard's 9 observations of thousands of Mahaleb seedling trees failed
to show a single infection of gummosis. It, therefore, seems that the
grower can use one or the other of these stocks, according to the soil
conditions.

The above recommendations necessitate considerable expense to the
grower. It, therefore, seems advisable to suggest, where there is little
danger from gummosis that the grower can contract with a nursery-
man to propagate his trees, using buds from the selected trees.

ACKNOWLEDGMENTS

The writers wish to express their appreciation of the help they have
received from the following persons in carrying out this work:

To Messrs. M. N. Wood and J. L. Stahl, Misses Ruth Amesbury
and Edna Russ, and other members of the Division who have rendered
assistance in the field and laboratory ; Messrs. S. H. Davidson, W. B.
Weidenthal, Bruce Hill, C. E. Seibert and W. S. Mallock, senior
students in the University who performed certain phases of the work
as thesis problems and without whose help it would have been impos-
sible to make so many crosses; Dr. W. L. Howard, who has given
service in suggestions and criticisms.

To the Earl Fruit Company, The Buck Fruit Company, The
Pioneer Fruit Company, H. A. Bassford, and Mrs. L. J. Payne of
Vacaville ; J. D. Copeland of Watsonville; J. W. Anderson of Davis;
A. B. Cory of San Leandro; H. G. Keesling and Mr. Di Fioro of
Santa Clara; J. Blunden, J. Doty, W. Grinnell, Mrs, I. Jonas, J.
McLain, and D. M. Searby of Sonoma County; and the Silva-Berg-
tholdt Nursery Company of Newcastle who have kindly allowed the
use of their orchards for certain experiments and without whose
cooperation most of the work could not have been accomplished.

28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION

LITERATURE CITED

i Gardner, V. R.

1913. A preliminary report of the pollination of the sweet cherry. Oregon
Agr. Exp. Sta. Bull. 116:1-40.

2 Hedrick, U. P.

1915. The cherries of New York. Part II of the 33d Ann. Eept. New York
Agr. Exp. Sta., p. 82.

s Wellington, R.

1923. Self sterility and self fertility of fruit varieties grown in New York.
New York Agr. Exp. Sta. (Geneva) Cir. 71:1-6.

* Crane, M. B.

1923. Report on tests of self-sterility and cross-incompatibility in cherries

at the John Innes Horticultural Institution. Jour. Pom. Hort.
Sci. 3:67-84.

s Hooper, C. H.

1924. Notes on the pollination of cherries applied to commercial cherry

growing. Jour. Pom. Hort. Sci. 3:185-190.

6 Florin, Rudolph

1924. Korsbarstradens pollinering (pollination of cherries). Meddelanden
fran pernamenta kommitten for Fruktodlinsforsck. Stockholm,
Sweden, 1:1-34.

7 Schuster, C. E.

1922. Pollination of the sweet cherry. Oregon Agr. Exp. Sta. Cir. 27:1-3.

(See also Burtner, J. C. Latest cherry pollination studies.

Better Fruit 18, No. 2:5-6.)
s Barss, H. P.

1918. Bacterial gummosis of stone fruits. Calif. State Dept. Hort. Mo.

Bull. 7:121-136.

s Howard, W. L.

1924. Unpublished data. California Agr. Exp. Sta.

STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION

BULLETINS

No. No.

253. Irrigation and Soil Conditions in the 346.

Sierra Nevada Foothills, California. 347.

261. Melaxuma of the Walnut, "Juglans

regia." 348.

262. Citrus Diseases of Florida and Cuba 349.

Compared with Those of California.

263. Size Grades for Ripe Olives. 350.
268. Growing and Grafting Olive Seedlings. 351.
273. Preliminary Report on Kearney Vine- 352.

yard Experimental Drain.

275. The Cultivation of Belladonna in Cali- 353.

fornia. 354.

276. The Pomegranate. 357.

277. Sudan Grass

278. Grain Sorghums.

279. Irrigation of Rice in California. 358.

280. Irrigation of Alfalfa in the Sacramento

Valley. 359.

283. The Olive Insects of California. 360.

285. The Milk Goat in California.

286. Commercial Fertilizers. 361.

287. Vinegar from Waste Fruits.

294. Bean Culture in California. 362.

298. Seedless Raisin Grapes. 363.

304. A Study of the Effects of Freezes on

Citrus in California. 364.

310. Plum Pollination.

312. Mariout Barley. 366.

813. Pruning Young Deciduous Fruit Trees.
317. Selections of Stocks in Citrus Propa- 367.

gation.
319. Caprifigs and Caprification. 368.

321. Commercial Production of Grape Syrup.

324. Storage of Perishable Fruit at Freezing 369.

Temperatures. 370.

325. Rice Irrigation Measurements and Ex- 371.

periments in Sacramento Valley,

1914-1919. 372.

328. Prune Growing in California.

331. Phylloxera-Resistant Stocks. 373.

334. Preliminary Volume Tables for Second- 374.

Growth Redwood.
835. Cocoanut Meal as a Feed for Dairy

Cows and Other Livestock. 375.

336. The Preparation of Nicotine Dust as

an Insecticide. 376.

339. The Relative Cost of Making Logs from

Small and Large Timber. 377.

340. Control of the Pocket Gopher in Cali- 378.

fornia.

343. Cheese Pests and Their Control.

344. Cold Storage as an Aid to the Market-

ing of Plums.

Almond Pollination.

The Control of Red Spiders in Decidu-
ous Orchards.

Pruning Young Olive Trees.

A Study of Sidedraft and Tractor
Hitches.

Agriculture in Cut-over Redwood Lands.

California State Dairy Cow Competition.

Further Experiments in Plum Pollina-
tion.

Bovine Infectious Abortion.

Results of Rice Experiments in 1922.

A Self-mixing Dusting Machine for
Applying Dry Insecticides and
Fungicides.

Black Measles, Water Berries, and
Related Vine Troubles.

Fruit Beverage Investigations.

Gum Diseases of Citrus Trees in Cali-
fornia.

Preliminary Yield Tables for Second
Growth Redwood.

Dust and the Tractor Engine.

The Pruning of Citrus Trees in Cali-
fornia.

Fungicidal Dusts for the Control of
Bunt.

Turkish Tobacco Culture, Curing and
Marketing.

Methods of Harvesting and Irrigation
in Relation to Mouldy Walnuts.

Bacterial Decomposition of Olives dur-
ing Pickling.

Comparison of Woods for Butter Boxes.

Browning of Yellow Newtown Apples.

The Relative Cost of Yarding Small
and Large Timber.

The Cost of Producing Market Milk and
Butterfat on 246 California Dairies.

Pear Pollination.

A Survey of Orchard Practices in the
Citrus Industry of Southern Cali-
fornia.

Results of Rice Experiments at Cor-
tena, 1923.

Sun-Drying and Dehydration of Wal-
nuts.

The Cold Storage of Pears.

Studies on the Nutritional Disease of
Poultry Caused by Vitamin A De-
ficiency.

CIRCULARS

No. No.

70. Observations on the Status of Corn 155.

Growing in California. 157.

Alfalfa. 160.

The Use of Lime and Gypsum on Cali- 161.

fornia Soils. 164.

Correspondence Courses in Agriculture. 165.
117. The Selection and Cost of a Small

Pumping Plant. 166.

House Fumigation. 167.

The Control of Citrus Insects. 170.
Afelilotus indica as a Green-Manure

Crop for California. 172.

Oidium or Powdery Mildew of the Vine. 173.
Feeding and Management of Hogs.

152. Some Observations on the Bulk Hand- 174.

ling of Grain in California. 178.

Irrigation Practice in Growing Small 179.

Fruit in California.

87.
111.

113.

127.
129.
136.

144.
151.

154.

Bovine Tuberculosis.

Control of the Pear Scab.

Lettuce Growing in California.

Potatoes in California.

Small Fruit Culture in California.

Fundamentals of Sugar Beet Culture

under California Conditions.
The County Farm Bureau.
Feeding Stuffs of Minor Importance.
Fertilizing California Soils for the 1918

Crop.
Wheat Culture.
The Construction of the Wood-Hoop

Silo.
Farm Drainage Methods.
The Packing of Apples in California.
Factors of Importance in Producing

Milk of Low Bacterial Count.

CIRCULARS — (Continued)

No.

184. A Flock of Sheep on the Farm.

190. Agriculture Clubs in California.

193. A Study of Farm Labor in California.

198. Syrup from Sweet Sorghum.

199. Onion Growing in California.

202. County Organizations for Rural Fire

Control.

203. Peat as a Manure Substitute.
205. Blackleg.

208. Summary of the Annual Reports of the

Farm Advisors of California.

209. The Function of the Farm Bureau.

210. Suggestions to the Settler in California.
212. Salvaging Rain-Damaged Prunes.

214. Seed Treatment for the Prevention

Cereal Smuts.

215. Feeding Dairy Cows in California.
217. Methods for Marketing Vegetables

California.

219. The Present Status of Alkali.

220. Unfermented Fruit Juices.

228. Vineyard Irrigation in Arid Climates.

230. Testing Milk, Cream, and Skim Milk

for Butterfat.

231. The Home Vineyard.

232. Harvesting and Handling California

Cherries for Eastern Shipment.

233. Artificial Incubation.

234. Winter Injury to Young Walnut Trees

during 1921-22.

235. Soil Analysis and Soil and Plant Inter-
relations.

236. The Common Hawks and Owls of Cali-

fornia from the Standpoint of the
Rancher.

237. Directions for the Tanning and Dress-

of Furs.

238. The Apricot in California.

239. Harvesting and Handling Apricots and

Plums for Eastern Shipment.

240. Harvesting and Handling Pears for

Eastern Shipment.

241. Harvesting and Handling Peaches for

Eastern Shipment.

242. Poultry Feeding.

243. Marmalade Juice and Jelly Juice from

Citrus Fruits.

244. Central Wire Bracing for Fruit Trees.

No.

245.
247.
248.

249.
250.

251.

252.
253.
254.

255.

256.
257.
258.
259.
260.

261.
262.
263.
264.

265.
266.

267.

268.

269.
270.
271.
272.

273.
275.

276.
277.

278.

Vine Pruning Systems.

Colonization and Rural Development.

Some Common Errors in Vine Pruning
and Their Remedies.

Replacing Missing Vines.

Measurement of Irrigation Water on
the Farm.

Recommendations Concerning the Com-
mon Diseases and Parasites of
Poultry in California.

Supports for Vines.

Vineyard Plans.

The Use of Artificial Light to Increase
Winter Egg Production.

Leguminous Plants as Organic Fertil-
izer in California Agriculture.

The Control of Wild Morning Glory.

The Small-Seeded Horse Bean.

Thinning Deciduous Fruits.

Pear By-products.

A Selected List of References Relating
to Irrigation in California.

Sewing Grain Sacks.

Cabbage Growing in California.

Tomato Production in California.

Preliminary Essentials to Bovine Tuber-
culosis Control.

Plant Disease and Pest Control.

Analyzing the Citrus Orchard by Means
of Simple Tree Records.

The Tendency of Tractors to Rise in
Front; Causes and Remedies.

Inexpensive Lavor-saving Poultry Ap-
pliances.

An Orchard Brush Burner.

A Farm Septic Tank.

Brooding Chicks Artificially.

California Farm Tenancy and Methods
of Leasing.

Saving the Gophered Citrus Tree.

Marketable California Decorative
Greens.

Home Canning.

Head, Cane, and Cordon Pruning of
Vines.

Olive Pickling in Mediterranean Coun-
tries.

The publications listed above may be had by addressing

College of Agriculture,

University of California,

Berkeley, California.

12m-3,'25