Sweet clover is adapted to a wider range of climatic conditions than
any of the true clovers and possibly alfalfa; in fact, it may be grown
successfully in any portion of the United States except, perhaps,
Florida, and in Florida trials with biennial yellow sweet clover,
annual sweet clover, and _Melilotus suaveolens_ have been successful.
Apparently neither the high temperatures of the South nor the cold
winters of the North severely affect the plants, provided there is
sufficient moisture in the soil. Comparatively little winterkilling
is experienced in Montana, Wyoming, Idaho, and North Dakota when the
seed is sown in close drills or broadcasted. Although approximately 50
per cent of the sweet clover seeded in rows 3 feet apart at Moccasin,
Mont., was killed by the unusually severe winter of 1915-16, no
winterkilling was noted in plats seeded in close drills.
Sweet clover thrives in the more humid parts of the country, as well
as in the semiarid regions where the rainfall is but three-fifths of
that required for the normal growth of such crops as red clover and
timothy. In the semiarid regions of the West sweet clover has proved to
be somewhat more drought resistant than alfalfa.