lium pratense_)
Oregon Experiment Station]

=Distribution.=--Medium red clover is thought to be native to Europe. It
was probably introduced into England some time early in the seventeenth
century. That it was attracting attention about the middle of the
century or a little later, is rendered probable by the fact that it is
discussed at considerable length in the third edition of Blyth's
"Improver Improved," published in 1662, while it is not mentioned in the
first edition, published in 1650. It was doubtless introduced into the
United States by the early colonists and at sundry times.

Medium red clover will grow in good form only in the temperate zone,
since it cannot stand excessive heat or excessive cold. The northerly
limit of its successful growth in North America is somewhere about 50 deg.
north latitude on the wind-swept prairies, but on suitable soils, and
protected somewhat by trees and winter snows, it will probably grow 10
degrees further to the north. In British Columbia, on the Pacific slope,
it will probably grow as far north as Alaska. But on prairies eastward
from the Rocky Mountains, it has not been grown with much success much
further north than 48 deg., unless under the eastern shadow of the Rocky
Mountains. Low temperatures in winter, where there is only a moderate
covering of snow, are far less fatal to clover plants than exposure to
the sweep of the cold winds. Even where the thermometer is not so low as
in the areas just referred to, such winds are particularly damaging to
the plants when they blow fiercely just after a thaw which has removed a
previous covering of snow. In some instances, one cold wave under the
conditions named has proved fatal to promising crops of clover over
extended areas.

In a general way, the southerly limit of vigorous and reliable growth
may be put at about 37 deg.. But in some localities good crops may be grown
further South, especially in some parts of Tennessee. Nor would it be
correct to say that medium red clover grows at its best in many
localities much south of 38 deg.. On the plateaus it can be grown further
South, where the soil is suitable.

This plant flourishes best in a moist climate. In fact, the abundance
and continuance of the growth for the season are largely dependent on
the amount of the precipitation, and on the distribution of the same
throughout the season. In climates in which it is usual for a long spell
of dry weather to occur in mid-summ