FIG. 192.—Young parts of red-clover stems showing characteristic hairiness. Enlarged to show hairiness. A, Italian, smooth. B, American, rough hairy. C, English, appressed hairy
RED Clover Strains—How They Behave
All red clovers are derived from the wild form of Trifolium pratense, a low-growing plant with branches lying nearly flat on the ground. From this, two main types have been developed—the single cut or late clovers, and the double cut. In the United States the single cut is known as mammoth, and the double cut as medium or June red.
These two types are distinguished mainly by the fact that the single cut is in full bloom two to three weeks later than the double cut and produces but one crop of stems in a year, while the double cut produces two crops of stems. The mammoth also has coarser and more hairy stems, but the development of this character depends somewhat on the soil and weather conditions. In the fall of the first year’s growth the mammoth is lower growing and more compact than the medium red and rarely produces stem growth. True American mammoth is grown only in North America. Imported “mammoth” or “sapling” has, in the department’s trials, invariably proved to be European double-cut clover. The American mammoth is a single- cut clover like the European single cut but is a very different strain, being coarse, strong growing, and very hairy, whereas the European type is smooth or with appressed hairs. The Altaswede, developed in Alberta, Canada, is a very good hardy type of European single-cut clover.
While these two main types, single and double cut, are common to red clovers in Europe and in America, the American type, though derived from the European, has developed characteristics of its own by which it may nearly always be known.
The American red clovers, whether single or double cut, are hairy, and the hairs stand at right angles to the stem (fig. 192). The stems are relatively coarse and the flower heads larger than those produced by European clovers, at least under American conditions. The European clovers are either nearly or quite as smooth as the Italian or the hairs lie flat against the stem and point up, as in English and French clovers. There is some variability in this character of hairiness, the American clover sometimes being very hairy and sometimes little hairy, but the characteristic appearance of the hairs can nearly always be seen on the young parts of the stems, especially just below the flower heads. It is very rare to find a plant of genuine American clover with smooth stem or with the hairs appressed to the stem. When such plants occur in numbers in any field it is certain evidence that mixed seed has been sown.
Besides the above characters visible to the eye, American clover is in America more winter hardy and more resistant to disease than the European type of whatever origin so far tested. Russian clovers have not yet been thoroughly tested. South American clover, at present imported only from Chile, is of the European type.
One American strain, the Tennessee anthracnose-resistant clover, has been selected for resistance to this disease, but in appearance is precisely like other American clovers. American clovers, whether grown in Canada or in any of the United States, are all alike in appearance, though there 1s some evidence that they are not all equally hardy or resistant to disease.