UNIVERSITY OF CALIFORNIA 
 
 COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY, CALIFORNIA 
 
 CIRCULAR 290 
 
 June, 1925 
 
 THE TANGIER PEA 
 
 Lathyrus tingitanus 
 By P. B. KENNEDY 
 
 Courtesy of F. G. Cuthbertson. 
 
 A crop of Tangier peas in full blossom at the Molera Ranch near Castroville, 
 Monterey County, California. 
 
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 INTRODUCTION 
 
 The following statement by such an eminent authority on economic 
 plants as C. V. Piper 1 of the United States Department of Agriculture 
 is sufficient encouragement to report the results of observations and 
 experiments with the Tangier pea in California. 
 
 "It has given the largest yields of green matter to the acre of any annual 
 legume grown in California. The dense growth chokes out weeds completely. It 
 is a good green manure crop but the seed has been hard to get. There is hope 
 that this difficulty may be overcome." 
 
 Kecent observations and experiments show that large yields of 
 seed of excellent quality can be grown in California. 
 
 The Tangier pea is an annual indigenous to northern Africa. It 
 has long been known in European gardens as an ornamental plant 
 and was first grown and recommended as a winter forage plant by 
 Dr. Trabut of Algeria. The earliest record I can find of its intro- 
 duction into the United States is given by C. R. Ball 2 in 1900. 
 
 "Chieharaca {Lathyrus tingitanus L.) — Plat 9-D-13 was seeded on May 28 
 with seed from Algeria (S. P. I. No. 3289). Only a thin stand was secured, but 
 the growth was very rapid. The plants were unaffected by the heat and drought 
 and reached a length of from 3 to 4 feet by the end of the season. They produced 
 numerous flowers during July, but no seeds set and the pods did not develop. 
 On November 15 the plants were still green and healthy in spite of several severe 
 frosts. This species closely resembles the bitter flat pea, but grew much larger. 
 It has not heretofore been cultivated in this country. It was introduced from 
 Algeria, where it is used as a winter forage, and is said to be free from the 
 poisonous properties found in so many of the flat peas. It is cultivated also in 
 the Canary Islands and Morocco, and is said to be hardy in southern Prance 
 where exposed to a temperature of 26 degrees F. " 
 
 Since the time of this first trial at Washington, D. C, numerous 
 experiments have been conducted by the United States Department 
 of Agriculture and the Agricultural Experiment Stations. Necessary 
 repeated experiments were usually prevented because of the loss of 
 the seed by shattering. The Seed and Plant Introduction numbers of 
 Lathyrus tingitanus grown by the California Station from 1900 to 
 1905 were 5585, 7637, and 21607. One lot designated 50/01 E 1x3 
 and received from Vilmorin and Company, Paris, under the name 
 L. japonicus proved to be L. tingitanus. A variety with one flower 
 on the peduncle, L. tingitanus uni flora (5/02 E VII. 2) has also been 
 grown. 
 
 i Piper, C. V., and Pieters, A. J., Green manuring. U. S. Dept. Agr., Farmers ' 
 Bull 1250:42, 1922. 
 
 2 Ball, C. E., Grasses and Fodder Plants on the Potomac Flats. U. S. Dept. 
 Agr., Div. Agrost., Cir. 28:14, 1900. 
 
CiRC. 290] 
 
 THE TANGIER PEA 
 
 Courtesy of P. A. Ingvnson. 
 
 Fig. 1. — Tangier peas grown under irrigation as a green manure crop on 
 Giffen Ranch near Fresno, California. 
 
4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Sornay 3 (p. 284) says: 
 
 " It is a first-class fodder plant and thrives very well. It is sown at the begin- 
 ning of the rains and its stems rapidly cover the soil. Cattle eat it readily. 
 Attempts should be made to acclimatize this legume in various sub-tropical 
 countries. ' ' 
 
 He errs in stating that Lathy rus tingitanus l ' grows wild in North 
 America." It is indigenous to Algeria. 
 
 * *f 
 
 Courtesy of U. S. D. A. 
 Fig. 2. — The roots of Tangier pea are well supplied with nodules. 
 
 Mr. W. E. Barker of Sequim, Washington, writes that on January 
 17, 1923, he 
 
 ' ' grew the Tangier pea on the poorest pieces of land on the farm ; land that had 
 been cropped to wheat for fifty years. It grew about 7 feet high and made an 
 impenetrable jungle. We harvested with a mower. I think this year I will try 
 
 3 Sornay, P. de, Green manures and manuring in the tropics. English trans- 
 lation by F. W. Flattely, 1916.) 
 
ClRC. 290] THE TANGIER p EA 5 
 
 tying a rope to the end of the sickle bar and have a man jerk the cut stuff away 
 from the standing. I know this is practised with a heavy vetch crop. I will 
 have about two acres in this year and I know of another acre field in Oregon. I 
 gave a lot of seed away here to other vetch growers and there should be quite a 
 quantity grown here in a year or two. It does not shell out here in the slightest, 
 which seems to be the main trouble in Oregon. The air here at harvest time is 
 very moist. ' ' 
 
 Similar reports have been received from Alabama, Oregon and Cali- 
 fornia, so that it would seem that the Tangier pea is destined to find 
 a useful place as a green manure (fig. 1) and as a forage crop not 
 only in California but throughout a wide range of territory in the 
 United States and elsewhere. As a spring sown crop it is favorably 
 mentioned in North Dakota and Indiana. 
 
 DESCRIPTION OF THE PLANT 
 
 The Tangier pea (see fig. 3) is an annual leguminous plant resem- 
 bling in a general way the ornamental sweet pea of the gardens. It 
 is a strong grower with numerous large nodules on its roots (fig. 2). 
 The plants grow from 3 to 7 feet long in a tangled mass (fig. 1), pro- 
 ducing a dense covering on the ground which enables it to choke out 
 weeds. It does not grow during the cold weather, but it shows the 
 effects of frost less than field peas, sweet clovers, vetches and other 
 winter legumes. The plant is smooth throughout, with coarse stems 
 and prominent stipules. The leaves consist of a pair of large leaflets 
 and a much branched tendril terminating the midrib of the leaf. 
 From the axils arise stalks which bear 2-3 flowered clusters of bright 
 scarlet flowers which are about the size of small sweet pea blossoms. 
 The pods are about S 1 /^ inches long and contain about seven seeds. 
 The seeds (fig. 4) are brown, elliptical, somewhat flattened and about 
 i/4 of an inch long. The hilum or scar is whitish and % of an inch 
 long. 
 
 RELATED SPECIES 
 
 The genus Lathyrus is represented by about 100 species occurring chiefly in 
 the northern hemisphere with a few in the mountains of tropical Africa and 
 some in South America. They resemble the vetches of the genus Vicia so closely 
 that only botanists are able to distinguish one from the other. Those that every- 
 one is familiar with are the annual ornamental sweet pea, Lathyrus odoratus and 
 the perennial everlasting sweet pea, L. latifolius of the gardens. 
 
 The grass pea, Lathyrus sativus, known also as Swiss pea, wedge pea, mission 
 pea and chickling vetch, is an annual plant and makes an excellent winter growth. 
 It is less subject to attack by aphis than the vetches, Vicia, and is strongly resist- 
 ant to the pea weevil. It is recommended for use in Canada in districts where 
 
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 Courtesy of U.S. D. A. 
 
 Fig. 3. — Upper portion of Tangier pea, showing leaves, stipules, flowers 
 
 and pods. 
 
Circ. 290] 
 
 THE TANGIER PEA 
 
 Fig. 4. — Seeds of the Tangier pea, natural size and enlarged five times. 
 
8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 the ordinary field pea, Pisum, cannot be grown on account of the ravages of the 
 pea weevil. The leafage makes good forage and the seed which is produced 
 abundantly, is used as human food especially in the Sudan, Eoumania and other 
 parts of Europe. Mr. A. F. Etters of Ettersburg, Humboldt County, California, 
 reports a yield of 2600 pounds of seed to the acre. The late Mr. L. E. Whiteside, 
 of Willow Creek, Humboldt County, states in a letter that the grass pea is not 
 bothered with pea weevil, that it is good hog feed, and that the seed does not 
 shatter readily. He recommends feeding it to laying hens and also considers it 
 superior to any dry pea for human food. In experiments at the various stations 
 it has been found that the tonnage of green material to the acre is very much 
 less than that of the Tangier pea. Seed of the grass pea is occasionally offered 
 for sale by the seedsmen of California. 
 
 The flat pea, Lathyrus silvestris, particularly the improved strain, Wagner's 
 flat pea, is a perennial offered for sale by seedsmen in Europe, Canada and the 
 eastern United States. It is said to grow successfully on poor land, even if sandy. 
 Owing to its deep root system, it is very resistant to drought. The crop has 
 been recommended for pasture and for hay. It has a high nutritive value, but 
 authorities disagree in regard to its palatability. Trials at the California Experi- 
 ment Station for many years have not been sufficiently promising to justify its 
 recommendation as a crop for this state. 
 
 In addition to the above mentioned, twelve other exotic species of Lathyrus 
 have been grown in our legume experimental gardens. With the exceptions of the 
 French pea, L. clymenum, and the ochrus pea, L. ochrus, none of them have, as 
 yet, given sufficient promise in the preliminary trials to be considered for forage, 
 green manure or seed. 
 
 In California there are at least a dozen indigenous species, some of which are 
 important range plants and others ornamental. The most interesting is what is 
 known as the Pride of California, Lathyrus splendens, with large, showy deep 
 rose purple flowers. Traveling on the highway between San Diego and Imperial 
 Valley one is much impressed by the gorgeous display produced by this plant as 
 it climbs through and over the chaparral. 
 
 Another, Torrey's wild pea, Lathyrus torreyi, occurs in patches in the Sierra 
 Nevada Mountains. It looks not unlike alfalfa and has creeping rootstocks. 
 Other native species are found in the marshes, by the sea shore and on the banks 
 in partial shade on the coast hills. Everywhere they are grazed to a greater or 
 less extent, but no experiments have been carried on to determine their value 
 under cultivation. 
 
 THE SEED CROP 
 
 Tangier peas have given excellent results in the southern United 
 States and in California and the chief objection to their general 
 introduction as a forage and green manure crop has been the difficulty 
 of producing the seed cheaply enough to compete with the vetches 
 (Vicia). 
 
 The seed shatters (fig. 5) readily from the pods when mature if 
 exposed to the hot sun in an arid atmosphere. This difficulty has 
 been very largely overcome by growing the crop in the fog belt and 
 harvesting the seed when the pods are ripe, but moist from the fog. 
 
Circ. 290] 
 
 THE TANGIER PEA 
 
 9 
 
 Commercial quantities of the seed are now available, largely through 
 the efforts of Mr. P. A. Ingvason, who contracted with Mr. J. E. 
 Phillips to grow a seed crop on the Molera ranch, 2% miles from 
 Castro ville, Monterey County, California. The crop was grown on 
 bottom land near the ocean on which sugar beets had been grown for 
 many years. 
 
 Fig. 5. — Pods of Tangier pea before and after expulsion of the seeds. 
 
 For seed production the method of seeding is to plant the seed in 
 rows three and a half feet apart in the fall after the first rains. The 
 time of planting will vary with the seasonal variations, but is usually 
 in November or December. The rate of seeding is about 25 pounds 
 to the acre. Owing to the prevailing cold winds from the ocean, the 
 growth is slow until spring, when it makes a very rapid growth 
 
10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 reaching a height of from 5 to 7 feet by the end of July, when growth 
 ceases. At this time the vines are so heavily laden with pods (fig. 6) 
 throughout their length that a settling (fig. 7) to 5 or 6 feet in height 
 takes place and the vines turn brown and are ready for harvest from 
 the first to the middle of August. 
 
 HARVESTING THE SEED 
 
 The tangled growth is so large and dense that difficulties are 
 encountered in cutting the material in such a manner as to be readily 
 available for threshing. The method has been to cut the material at 
 the base near the ground with a mower and to roll the cut portion 
 (fig. 8) out of the way of the next cut, by hand. It is then bunched 
 and hauled to the thresher (fig. 9). The atmosphere during the 
 harvesting process should be quite moist so as to reduce the shattering 
 (fig. 5) of the seed to a minimum. 
 
 A method sometimes advocated for heavy crops of vetch is to tie 
 a rope to the end of the sickle bar and have a man jerk the cut 
 material away from the standing. No doubt other methods and 
 machinery could be devised that would reduce the labor cost very 
 considerably. 
 
 No trouble is encountered in separating the seed from the pods 
 and straw by any ordinary bean or pea threshing machine and as 
 there are no weeds, a fine quality of seed is produced that needs little 
 or no additional cleaning. One ton of seed to the acre may be ex- 
 pected and two or more tons to the acre have been produced. The 
 seed weighs 60 pounds to the bushel. 
 
 There is every reason to believe that, as the conditions for growing 
 the seed exist over a wide area on the coasts of California, Oregon 
 and Washington, the Tangier pea will soon find a permanent place 
 in American agriculture. 
 
 A very large tonnage of straw remains after threshing. That it 
 is valuable as a fertilizer may be gathered from the following analysis 
 furnished by the Division of Nutrition of the College of Agriculture. 
 
 
 Analysts of Tangier Pea Straw 
 
 
 Moisture 
 
 Protein Fat Ash Fiber 
 
 N.F.E. 
 
 10.00% 
 
 6.42% 1.78% 10.64% 37.10% 
 
 34.06% 
 
 Average of Analyses of Sixteen Kinds of Bean Straw* 
 
 Moisture Protein Fat Ash Fiber N.E.F. 
 
 11.07% 5.68% 1.52% 6.97% 41.10% 33.63% 
 
 * Hendry, G. W., et al., Bean culture in California. California Agr. Exp. Sta., 
 Bull. 294:343, 1918. 
 
Circ. 290] 
 
 THE TANGIER PEA 
 
 11 
 
 
 todfad 
 
 / --< 
 
 Fig. 6. — A dense growth of Tangier peas six feet tall, heavily laden with pods 
 and ready to harvest. All weed growth has been effectually smothered. 
 
 Fig. 7. — A mature seed crop of T; 
 
 pea ready to harvest. Molera Kanch, 
 
 near Castroville, Monterey County, California. 
 
12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 A comparison of the analyses indicates that Tangier pea straw 
 has about the same value as an organic fertilizer as the average bean 
 straw now utilized in the orchards of southern California. As the 
 Tangier pea can be grown for seed on the same land now growing 
 commercial crops of sugar beets, potatoes, mustard seed and other 
 crops, it would seem advisable to spread the straw on the land where 
 it is grown, and plow it under as a fertilizer. It might also be found 
 valuable in the orchards of the Santa Clara Valley and other fruit 
 sections in the vicinity. 
 
 THE TANGIER PEA FOR GREEN MANURE 
 
 The large and abundant nodules (fig. 2) on the roots of the Tan- 
 gier pea make it an excellent nitrogen gatherer. Its ability to with- 
 stand cold and frost without permanent injury is also in its favor 
 as a winter grower. 
 
 The chief aim in growing a green manure crop is to produce as 
 large a tonnage as possible of green material, preferably of a legumin- 
 ous crop, that can be plowed under and incorporated with the soil. 
 Tangier peas produce a heavy tonnage. Mertz shows that a five year 
 average tonnage on light sandy loam under irrigation at the Rubidoux 
 Experiment Farm, Riverside, California, was 13.7 tons to the acre, 
 the same as that of bitter clover (Melilotus indica). The only legume 
 producing a greater tonnage was purple vetch (Vicia atropurpurea) 
 with 20 tons to the acre, but this was for a two-year period only, and 
 therefore not strictly comparable. The average of nine different 
 kinds of legumes was 13.0 tons to the acre. 
 
 The question of whether this or that legume is the ''best" can be 
 determined only by a series of experiments over a long period of 
 years. No single legume gives equally good results every year in a 
 given district. One year the small seeded horse bean will make a four 
 foot growth by January first, and the next year only a foot of growth 
 will be produced because of the ravages of aphis. Bitter clover makes 
 a very poor growth in cool, dry winters, as in the season of 1924-25, 
 when it was only four inches high by the middle of January. Purple 
 vetch is one of the best of the new legumes, but it is severely attacked 
 by aphis in certain seasons. 
 
 Another feature not sufficiently considered in the growing of crops 
 in general is that nearly all crops are subject to certain diseases and 
 insect pests so that by changing the host plant the breeding grounds 
 are frequently interfered with. 
 
 g Mertz, W. M., Green manure crops in southern California. California Agr. 
 Exp. Sta., Bull. 292:10, tab. 2, 1918. 
 
CiRC. 290] 
 
 THE TANGIER PEA 
 
 13 
 
 Fig. 8. — A field of Tangier peas being harvested for seed on Molera Ranch, 
 near Castroville, Monterey County, California. 
 
 
 I 
 
 •*M^j*» .* 
 
 Fig. 9. — A seed crop of Tangier peas bunched and ready to haul to the 
 thresher, Molera Ranch, near Castroville, Monterey County, California. 
 
14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 All of the above mentioned legumes will make a satisfactory green 
 manure crop in certain seasons, but the same legume will in no case 
 make the most satisfactory crop every year. It is safest, therefore, 
 to rotate the best known leguminous green manure crops for a ten- 
 year period. The following is a suggestion for a ten-year rotation: 
 
 Bitter clover (Melilotus indica), two years. 
 
 Purple vetch (Vicia atropurpurea) , two years. 
 
 Tangier pea (Lathy rus tingitanus) , two years. 
 
 Small seeded horse bean (Vicia fab a var. minor), two years. 
 
 Fenugreek (Trigonella foenum graecum), two years. 
 
 It may be found after further experimentation that in certain 
 districts one or more of these legumes may be supplanted in the rota- 
 tion by other varieties. Some very promising winter growing legumes 
 now under experiment are the spurred vetch (Vicia calcarata) , the 
 one flowered vetch (Vicia monanthos) , and species of lupines. It 
 seems probable that when a more complete knowledge of the growth 
 requirements for each legume is available that a definite mixture of 
 seed of a number of different legumes will be found to produce the 
 largest average tonnage of green stuff to plow under over a period 
 of years, and make it practically certain that a good cover crop will 
 be produced every year, notwithstanding the seasonal variations. 
 
 In the early experiments of the California Experiment Station 
 on small trial plots from 1900 to 1905, with irrigation, a yield esti- 
 mated at from 17 to 19 tons of green tops to the acre was produced 
 by April 20 from October seeding in southern California. Without 
 irrigation and with a rainfall of less than 10 inches the results were 
 not promising and in very dry years the crop was a complete failure. 
 One instance is recorded from Redlands where, on red clay loam with 
 the seed broadcasted between the rows of an orange orchard on Octo- 
 ber 7, 1905, and with ample irrigation, an estimated yield of 35 tons 
 to the acre of green stuff is reported by April 4, 1906. 
 
 THE TANGIER PEA AS A FORAGE PLANT 
 
 The experiments that have been conducted with the Tangier pea 
 have been mainly in regard to its use as a green manure. Yet it is 
 highly regarded by Trabut in Algeria and by some of the experiment 
 stations in the United States as a forage plant. The leafage is both 
 palatable and nutritious and no deleterious effects have been recorded 
 from feeding it to livestock. At Vacaville, Solano County, California, 
 
CIRC. 290] THE TANGIER PEA 15 
 
 on alluvial deposit soil verging on adobe, without irrigation, an esti- 
 mated yield of three tons of hay to the acre was obtained. The seed 
 was planted on November 17 and harvested May 1. It received a 
 seasonal rainfall of 17.29 inches with a minimum temperature of 
 30 degrees F. 
 
 At San Lorenzo, Alameda County, California, on alluvial deposit 
 soil, from seed sown October 30 and grown without irrigation a 
 growth five feet in height was obtained by April 23. The tempera- 
 ture dropped to 26° F. in February, but the crop was only slightly 
 injured, and later recovered. Under especially favorable circum- 
 stances estimated yields of as high as nine tons to the acre have been 
 reported in California. As it has been shown that a dense crop seven 
 feet in height can be grown wuthout irrigation and under field con- 
 ditions, it is plain that the Tangier pea should be given a thorough 
 and extended trial for forage purposes in all the coast counties of 
 California from the Monterey Bay region (frontispiece) north to the 
 Oregon boundary line. 
 
 20ro-6,*25