28 BULLETIN 1301, U. S.. DEPARTMENT OF AGRICULTURE 
headed back each year. All pruning in these blocks is done before 
the trees start growth in the spring. 
Varieties used in the pruning experiment are Whitney and Lyman 
crabs; Wealthy and Hibernal apples; and Wyant, Wolf, Waneta, 
Cheney, Opata, and Compass plums. Good stands of all varieties 
were obtained. 
WINTER PROTECTION 
Winter protection of some kind is essential to the growth of certain 
fruits on the northern plains. In other cases it may be desirable for 
a few years until the plants become established. Protection against 
mice and rabbits is generally necessary. 
Mulching with straw or old manure is the most common form of 
winter protection that has been employed at the station. Straw 
mulching of apples and plums has been considered. A common 
ractice has been to protect such tender fruits as pears and cherries 
ie piling straw or old manure around the trunks of the trees, and 
experience indicates that winterkillng may be materially reduced in 
this way. A straw mulch from 6 to 8 inches thick has been found 
satisfactory for strawberries. 
Protection can also be obtained by covering the plants with soil. 
This method has been found most satisfactory for raspberries, which 
commonly kill down to the surface of the ground if not protected. 
Grapes also have been brought through the winter in this way while 
unprotected vines were killed, but sometimes they have winterkilled 
even when covered with soil. Gooseberries and currants generally 
are able to survive the winter without such protection, although some 
varieties of gooseberries need covering. In the winter of 1914-15 
covered gooseberries came through in good condition, while unpro- 
tected bushes were severely damaged. In general, however, unpro- 
tected gooseberries have yielded as well or almost as well as protected 
ones; if the hardier varieties are chosen, covering should not be 
necessary. Even tender varieties of trees bent over and covered 
with soil pass the winter without serious injury. Of course, such 
see protection with trees would be practicable only on a small 
scale. 
Whitewash is being tested as a means of winter and early-spring 
protection. Whitewashed twigs heat up less during the warm sunny 
days of late winter and early spring, and as a-consequence the dormant 
bce is prolonged and the danger from late spring frosts is lessened. 
t may also lessen desiccation (drying out) of the twigs during the 
winter, which may be responsible for much winterkilling. Every 
third row in the pruning experiment is whitewashed, but it is too 
early to draw conclusions. 
Protection from rabbits and mice generally has been accomplished 
with wood-veneer wrappers, tree paints, or poisoning. When the 
trees are grown in bush form it is difficult to protect by wrapping or 
painting, and poisoning has been found the most practicable method. 
STOCKS AND TOP-WORKING 
Hardy stocks are just as important as hardy varieties. Conse- 
quently, testing of different stocks for fruit trees has been an im- 
portant line of work. 
Apples have been tested on Pyrus baccata, French crab, Vermont 
crab, Paradise, Doucin, Malus coronaria, Crataegus mollis, Yankton 
