BLIGHTS OF CONIFEROUS NURSERY STOCK. ALL 
established. This method tends to protect the transplants during the 
period when they have the least absorbing root surface and exposes 
them to the sun during the larger part of the growing period, so 
that by the end of the season the trees should be thoroughly hard- 
ened and ready to stand field planting. Shade will always be a 
useful adjunct in preventing sun scorch, though the extent to which 
it should be used will vary greatly with different nurseries. 
Crowding should be avoided in order to avoid sun scorch. What 
constitutes crowding varies greatly at different nurseries and with 
different species. At Halsey a second-year seed bed containing 75 
Scotch pine per square foot is crowded. At Monument 150 Douglas 
fir per square foot do not crowd each other seriously at the same age. 
Transplants should be given much more room than seedlings. The 
older commercial nurseries often practice thinning in their older seed 
beds and generally give their transplants a great deal of space. Be- 
cause of the extra cost of weeding and cultivating large areas and the 
limited space at some nurseries, 1t 1s sometimes probably cheaper to 
crowd stock in a small space and prevent scorch by increased shade 
or watering. 
Extremely sandy soils should be avoided, and any deficiency in 
humus should be counteracted by manure and soiling crops, so as to 
increase the water-holding power of the soil. Nurseries on very sandy 
soils in the Northeastern States appear to have more trouble from 
sun scorch than western nurseries, which have drier climate but 
somewhat heavier soil. Windbreaks and surface cultivation are also 
undoubtedly helpful in preventing sun scorch. 
WINTERKILLING. 
Winterkilling is generally understood to mean death as a result 
of drying when the soil and roots are so frozen that the amount of 
water given off from the leaves can not be replaced to a sufficient ex- 
tent by absorption from the soil. In this way its cause is funda- 
mentally the same as that of sun scorch, the difference being that it 
occurs while the soil is frozen. Alternate freezing and thawing is 
considered important in bringing about damage. This may be due 
simply to the increased loss of water from the needles during warm 
periods which do not last long enough to thaw out the soil materially. 
In the West, the warm winds known as “ chinooks” produce such 
sudden very warm periods in the midst of the coldest weather that 
not only small plants but even the largest forest ‘trees are sometimes 
_ killed.t 
1 Hedgcock, G. G. Notes on some diseases of trees in our national forests. III. Phy- 
topathology, v. 3, No. 2, p. 112-113, 1913. 
Hartley, Carl. Notes on winterkilling of forest trees. Forest Club Annual [Uni- 
versity of Nebraska], v. 4, p. 41-46, 1912. 
