Sb m- c(p^ r¥^ 018 451 889 2 f 1 \NNUAL WHITE SWEET CLOVER AND STRAINS OF THE RIENNIAL FORM A. J. PIETERS Agronomist in Charge of Clover Investigations and L. W. KEPHART Scientific Assistant UNITED STATES DEPARTMENT OF AGRICULTURE DEPARTMENT CIRCULAR 169 Contribution from the Bureau of Plant Industry (Office of Forage-Crop Investigations) WM. A. TAYLOR, Chief Washington. D. C. Issued April, 1921 WASHINQTON : GOVERNMENT PRINTINQ OFFICE : 1921 ;]^&^' utpraj^ ANNUAL WHITE SWEET CLOVER AND STRAINS OF THE BIENNIAL FORM. CONTENTS. Page. Annual white sweet clover 3 Wild annual white sweet clover 6 Can the annual plants he distin- guished from those of the hiennial form? 7 Can the seed of the annual he dis- tinguished from that of the bien- nial form? 8 Variations in annual white sweet clover 1(1 Page. Annual blossoming biennial forms. _ 12 Uses for annual white sweet clover_ 12 Value of differeiit varieties of bien- nial white sweet clover 17 Strains of biennial white sweet clover 18 Grundy County sweet clover 19 Arctic sweet clover 20 Summary 21 ANNUAL WHITE SWEET CLOVER. In the spring of 191G Prof. H. D. Hiiorhes, of the Iowa Agricul- tural Experiment Station, discovered that certain white sweet-clover plants growing in the greenhouse Avere blooming the first year. Later in the season Mr. H. S. Coe, of the United States Department of Agriculture, found similar plants at both Redfield, S, Dak., and Fargo, N. Dak., in the regional strain plats sown with Alabama seed. The other plats showed no annuals. Prof. Hughes distributed small quantities of seed to agricultural experiment station workers and to some private individuals, some of whom have propagated the seed and sold it at high prices. During the season of 1920 one firm contracted for 20 bushels of seed at $300 a bushel. Naturally, much interest was aroused by statements of the rapid growth of this variety. During the past two years many articles have appeared in the agricultural press commending the crop very highly. It has even been predicted that it would revolutionize the agriculture of the corn belt. The nature of this new variety is cer- tainly such as to indicate that it may have important possibilities. Whether all of these hopes will be realized remains to be seen. Though Prof. Hughes was the first to call the attention of agrono- mists to the variety, it had probably been observed by the late Prof. S. M, Tracy as early as 1898. In "Forage Plants and Forage Re- sources of the Gulf States," he says, writing of MeJilotus alba^ " a few plants will produce seed the first year and a few will live three years." It is, however, uncertain whether Prof. Tracy referred to genuine annual plants or to the biennial form which sometimes blooms 3 4 Department Circular 169, IL S. Dept. of Agriculture. the first year. In 1917, when Mr. Tracy's- attention was called to the discovery of the annual, he insisted that the words quoted above referred to the annual variety. Some time before 191G Dr. W. B. Gernert, then of the Illinois Agricultural Experiment Station, dis- covered the annual variety and propagated it to some extent. In a letter dated April 15, 1918, Prof. C. G. Hopkins said : " The Illinois station has been growing the annual white sweet clover for several years. In 1917 we harvested about 5 bushels of seed, and we now have about 10 acres of this crop growing." In 1914 the Illinois Agricultural Experiment Station had photographs and notes on this variety together with records of the comparative weights of the Fig. 1. — Roots of white sweet clover : Left, wild growth of the biennial form ; center, biennial form from a cultivated row ; right, annual form from a cultivated row. annual and the biennial forms. Dr. Gernert has kindly supplied from these records the data show^n in Table I. Table T. — Growth data of the annual and Mcnnial forms of ichitc stircct clover at the Illinois Auricultural Exiterinient station. Speciflcation. Annual form. Biennial form. Height centimeters. . 157 88. C2 8.93 119 Air-dry weight: Top grams.. 117.54 Root do 33.69 Annual White Sweet Clover. The annual variety was also observed in Arkansas in 1916. Tlie writers are indebted to Dr. Gernert for a reference to Gleanings in Bee Culture, Decem- ber 15, 1916, where this observation is recorded. There is no record at the Iowa Agricul- t u r a 1 Experiment Station showinc; where the original seed out of which the annual variety was selected was grown. The Illinois strain was selected from a lot of seed purchased in Falmouth, Ky., and reported to have been grown in Ala- bama. The plants found at Redfield and Fargo were in plats sown with seed from Alabama. Mr. Coe described the annual variety, giving it the name of MelUotus alha x'av. annua.^ and called at- tention to the botan- ical characters in w h i c h it differed from the biennial plant. The annual has a smaller, more woody root than the bien- nial form, and crown or resting buds are not formed. (Fig. 1.) The stems, branches, leaves, flowers, pods, and seeds are indistin- guishable from those of the biennial form, but during the season of seed- ing the plant grows more rapidly, blossoms, fruits, and dies. (Fig. 2.) Fig. 2. — A group of annual white s\v<'i>t-cIover plants 4 months after seeding. The plants vary in size and development. 6 Department Circular 169, U. S. Dept. of Agriculture. WILD ANNUAL WHITE SWEET CLOVER. The seed of annual white sweet clover that has been sold so far and most of that on the market during 1920 was produced from the Iowa strain. During the summer of 1920, however, interest in this variety was aroused in Alabama, in Hale and Perry Counties, where it occurs with the biennial form, and some seed from that source will doubt- less be on the market later. It is not possible at present to place any limit on the range in which annual white sweet clover may be growing wild. It has been found chiefly in Alabama, but is also present in natural wild growths of Melilotus alha about Washington, D. C. In waste places near the Potomac River in Virginia, just outside of Washington, there are considerable areas used as dumping places for mortar and building refuse. These dumping grounds are covered every summer with a dense growth of sweet clover, and a few annual plants are to be found. Their number would equal but a small fraction of 1 per cent of the total plant population, however. How, when, or where the annual variety originated is not known. Statements have appeared to the effect that the ver}^ hill slope in an Alabama county on which this variety originated had been located. It seems doubtful whether such claims can be taken seriously, with the evidence at hand. As already stated, it is probable that this variety was observed in the South as early as 1898. The fact that annual specimens were found about Washington after careful search over considerable areas of wild growth suggests that the tendency to sport in this way may be inherent in Blelilotus alha. Conditions in Alabama may have been especially favorable for the increase of this variety, thus giving it greater prominence there. So far a very superficial examination has sliown that the plants occur in sufficient abundance for seed gathering only in the counties in Alabama mentioned. The harvesting of seed appears to be done mainly about Uniontown and Newbern. Throughout this section the annual plants are found either mixed with the biennial form or in more or less pure growths in fields or in patches. Since the two varieties occur in more or less mixed stands, the purity of the seed gathered depends on the ability of the person harvesting to distin- guish the two forms. In the latitude of Washington, D. C, the annual plants begin to bloom at about the time the biennials are in full bloom. Both forms have, however, a long flowering period, and during most of the time from the middle of July to September both annuals and biennials may be found bearing flowers and young or mature pods. Annual White Sweet Clover. 7 CAN THE ANNUAL PLANTS BE DISTINGUISHED FROM THOSE OF THE BIENNIAL FORM? The annual and the biennial forms, of course, can be readily dis- tinguished by the roots, as already explained. When harvestino; seed, Fig. 3. — Typical biennial white sweet-clover plant during the second season. Note the dead stubble of the previous year's growth (a) and the many branches from the crown buds. however, one can not examine all the roots. When the growth of the biennial form in bloom is typical, it has also a distinctive habit. The slender stem of the first season's growth is killed and is represented 8 Department Circular 169, U. S. Dept. of Agriculture. by a stub ot dead tissue. Around this stub and coming from the crown are two to several strong branches, the growths from the rest- ing buds (fig. 3-) . Such branches never occur in the annual form. The habit of growth of the biennial is not always typical, however. In every natural stand, .especially if it is thick, there are a number of plants with apparently one central stem only. An examination of the root will show that this stem is not truly central, but has come from a lateral resting bud. By the suppression of the other buds and the total disappearance of a central stem, the one branch appears to be a central stem (fig. 4). How large a percentage of such plants may Fiu. 4. — Stems and roots of biennial wtiite sweet clover. The four stems at the left may readily be mistaken for those of annuals. Note the old stubbles on several plants. occur in a natural stand of biennial sweet clover is not known, but it can readily be seen that where a mixed growth of annuals and bi- ennials occurs such plants are easily mistaken for annuals. Great care will be necessary, therefore, when harvesting seed from such a stand. CAN THE SEED OF THE ANNUAL BE DISTINGUISHED FROM THAT OF THE BIENNIAL FORM? The statement has been made that the seed of the annual white sweet clover can be distinguished from that of the biennial form, Annual White Sweet Clover. 9 but the Seed Laboratory of the United States Department of Agri- culture has been unable to confirm this statement. The writers secured from a reliable correspondent in Wilcox County, Ala., a large number of samples taken from both annual and biennial plants of white sweet clover. Samples were also obtained by an agent of the United States Department of Agriculture from lots of seed harvested in Alabama as that of the annual variety. Further samples were taken from plants grown from the department strain of the annual form. All of these, together with authentic biennial seeds and commercial biennial seeds, were submitted to Mr. F. H. Hillman, of the Seed Laboratory, with the request that a study be made to determine whether any constant and reliable difference exists by which seed of the annual may be certainly distinguished from that of the biennial form. His report is given herewith. The 62 samples of seetl of sweet clover, part from annual and part from biennial plants, were received with your letter of August 31. These samples are our Nos. 724077 to 72413S, inclusive. I have examined them with a view to finding means by which seed from annual plants may be distinguished from that from biennial plants. Both pods and seeds have been carefully examined under a low-power com- pound microscope, and I fail to find any external characteristics by which pods or seeds from annual plants may be distinguished from those from biennial plants. Pods from different lots sometimes differ considerably in appearance, ap- parently due to conditions prior to harvesting, but this is evident alike in pods from both annual and biennial plants. Likewise, differences in the seed are observable, but they appear in seed from both types of plants. Later, seed of the Iowa strain of the crop of 1920 was secured from the two largest producers. This seed could not be distinguished from that of the biennial form. It appears, therefore, that no one can tell whether any particular lot of seed is that of the annual or the biennial form. This is of great importance, in view of the present interest in the variety and the high prices being paid for seed. To the possibility of honest error, especially in the case of wild seed, must be added the temptation that always exists in such cases for dishonest dealers to sell seed of one variety for that of the other or to mix the seed. Buyers are cautioned to use care and whenever possible to demand the pedigree of the seed offered. The strain developed by the United States Department of Agriculture has not been generally distributed, and samples of the Illinois strain are reported to have been sent only to several persons in Edgar County, 111., in the spring of 1919 and again in 1920. All commercial lots offered during the season of 1920-21 as specially grown should therefore trace back to the Iowa strain. 34985°— 21 2 10 Department Circular 169, U. S. Dept. of Agriculture. VARIATIONS IN ANNUAL WHITE SWEET CLOVER. The biennial white sweet clover is extremely variable, varying in size, habit, productiveness, and date of maturity. Many of the varia- tions are certainly due to local conditions, such as the presence of an abundance of lime or the absence of lime. Many variations are, however, undoubtedly inheritable. The annual white sweet clover is also extremely variable. During the summer of 1920 the United States Department of Agriculture iSj55:5!SS:?9!i5s3SI58?ii5^5;i^^§^Sii?S^:??^?^^$:§!?3:^$^$$^55§Si3^1?!§^?§§^S!8S18S8fe§SS s?!5^J? Fig. 5. — Relative heights in inches on July 16 of 65 annual white sweet-clover plants grown consecutively in row 10001-C by the United States Department of Agriculture. sowed several rod rows to various lots of annual white sweet clover, the seed being selected from the department strain, from the Iowa strain, and from the Illinois strain. So far as is loiown, none of these selections were from self-fertilized individual plant's. The plants of each row were thinned to stand from 6 to 8 inches apart in the row. All the plants of a lot thus had practically identical soil conditions. The diagram (fig. 5) represents the variations in height of 65 consecutive plants in the row of the department's selection No. 10001-C. Seed was sown on April 10, 1920, and measurements "Were made on July 16, at which time most of the plants were coming Annual White Sweet Clover. 11 into bloom. The plants in the other rows showed similar variations. In date of blossoming there was also considerable variation. The first observation was made on July 14, when fully opened racemes were found on many plants. These were all removed. Later observa- tions showed that' different plants came into flower at various times and as late as August 10. The diagrams (fig. 6) show the relative percentage of all the plants in a lot that came into flower at the dates specified. Much variation was also noted in branching habit, leafiness, and seed-producing capacity.^ ^^ . I ^^ ^ ^ !^ "0 N s ^1 b h S6 ^ ^ 5 O 5 ^i S> ^ ^ ^ "^ ^ ^1 ^