36 BULLETIN 1276, U. S. DEPARTMENT OF AGRICULTURE 
in some years but on the average mature at almost the same time 
as Kharkof. It should be noted that Turkey, C. I. No. 1558, in 40 
station years matured only 0.3 of a day later than Kharkof, while 
another commercial lot of Turkey, C. I. No. 1571, matured 0.2 of a 
day earlier than Kharkof, indicating that the two varieties are prac-_ 
tically identical in this character. , 
A few varieties, including Blackhull and Kanred, are definitely 
earlier than Kharkof. Kanred in 38 station years was 1.1 days 
earher than Kharkof. 
Among the soft red winter wheats, Buffum No. 17, Lofthouse, 
Minhardi,*and Odessa are distinctly later than Kharkof. The winter 
varieties of white wheat and club wheat grown in these experiments 
also are from one to five days later than Kharkof on the average. 
WINTER SURVIVAL 
Winterkilling is an important limiting factor in winter wheat pro- 
duction in the Great Plains area, especially in the Northern States. 
The winterkilling of wheat sometimes occurs in the Great Basin 
area, although hard red winter wheats usually are not injured by the 
low temperatures there. Winterkilling in the semiarid Western 
States usually is due to a combination of low temperatures, deficient 
moisture, soil blowing, soil heaving, ice covering, and possibly other 
factors. During the period of the experiments reported in this 
bulletin all of the winter wheat varieties were completely winter- 
killed at Williston, N. Dak., in 1912 and 1917; at Dickinson, N. Dak., 
in 1918 and 1920; at Moccasin, Mont., in 1916 and 1917; at Newell, 
S. Dak., in 1918; and at Akron, Colo., in 1909. When all varieties 
were killed the results are not used in computing the relative survival 
of the varieties. When no winterkilling occurred the relative hardi- 
ness can not be determined, and the data are not used in computing 
comparative hardiness. Estimates of the winter survival were made 
either by observation or by counting the stand in small areas in the 
plats. The percentage of winter survival was not reported in many 
expermments. Data on the relative survival of the winter-wheat 
varieties were recorded during 40 station years at the stations in the 
Great Plains area. Survival data also were recorded during five 
station years at three stations in the Great Basin area, but the 
behavior of some of the more tender varieties indicated that the 
differences in the extent of winterkilling were not due principally to 
differences in hardiness. The average percentage of winter survival 
of the varieties is shown in Table 20. The average survival of the 
standard Kharkof during 38 station years in which partial winter- 
killing occurred was 64.3 per cent. Most of the hard red winter 
varieties were less hardy than Kharkof. Those showing the greatest 
hardiness compared with Kharkof during five or more station years 
are Turkey (C. I. No. 3084), Kharkof (C. I. No. 4207), Minturki, 
Karmont, and Beloglina. In these experiments Kanred was slightly 
less hardy than Kharkof, while Blackhull shows an average survival 
of 10 per cent less than Kharkof. 
Two varieties of soft red winter wheat, Diehl-Mediterranean end 
Nebraska No. 28, are distinctly less hardy than Kharkof, while two 
other varieties, Buffum No. 17 and Minhardi, are among the most 
hardy varieties of winter wheat grown in these experiments. 
