86 FARM GRASSES OF THE UNITED STATES 
soils, might replace it altogether. They are also bet- 
ter adapted to sowing with clover, since they mature 
at the same time that clover does. Spring sowing is 
particularly objectionable in the South, and the farther 
south the more undesirable it becomes. In the first 
place, spring-sown grass is likely to be taken by weeds, 
especially by crab-grass. It is also liable to be killed 
by the summer heat. 
On the northwestern prairies the best practice is to 
prepare land in fall and sow grass and clover in spring 
without a nurse crop. ‘There is usually not moisture 
enough for both grain and grass, while fall-sown grass 
would hardly stand the rigor of the first winter. The 
same is generally true on the irrigated lands of 
Wyoming and Montana. On the upland prairies of 
eastern Washington, eastern Oregon, and northern 
Idaho, spring sowing is necessary, for during the win- 
ter there are liable to occur periods of clear weather 
in which the ground freezes at night and thaws in day- 
time, a condition quickly fatal to young grass. But 
in this section the land cannot be prepared in autumn 
with safety for two reasons: first, the winter rains 
would wash it, for the country is quite rolling; 
secondly, the dry winds of early spring would quickly 
rob the bare soil of its moisture, while a covering of 
wheat-stubble prevents this. The best plan is to plow 
the land in early spring, harrow it down, and sow the 
seed at once. At low altitudes in this section, as 
around Walla Walla and Pendleton, fall sowing is 
successful. In western Washington, western Oregon, 
and northern California timothy is nearly always sown 
in the fall. On sandy land in that section clover may 
