MISSOURI BOTANICAL GARDEN BULLETIN 101 
ground has been frozen two or more feet deep, for under such 
conditions its temperature will soon equalize itself with 
that of the surrounding air, despite a thick covering. The 
function of a protective dressing lies chiefly in its reduc- 
tion of evaporation, which is very excessive during dry 
winters of light snowfall. Being “teaiis, the roots cannot 
respond to the drain upon the plant’s system, and the parts 
exposed to the action of the atmosphere consequently 
shrivel. A mulch also serves a useful purpose in prevent- 
ing alternate thawing and freezing, which is particularly 
injurious in heavy soils, causing the heaving out of plants 
with irreparable damage to the roots. Excessive packin 
and baking of the ground through the weight of snow an 
rain is also eliminated. 
The chief protection afforded trees and shrubs usually con- 
sists of a mulch 4—6 inches deep of well-rotted manure, 
straw, or other litter, placed over the roots when planted in 
the fall. If planting is to be delayed until spring, the trees 
or shrubs may be heeled in; i. e., the roots are laid in a 
shallow trench, covered with well-drained, sandy soil, and 
later given a covering of straw. Occasionally, newly 
planted, large trees need protection over winter in order to 
acclimate them ually to a colder climate than that of 
their nativity. Such trees should be given a mulch at the 
roots, while the tops should be tied close to the main trunk, 
covered with a 6-inch thickness of straw or hay, and finally 
tied with burlap. The latter serves to keep the wind out 
and sheds water. Where available, hemlock boughs effec- 
tively replace the straw and burlap. 
Among shrubs the rhododendrons as a class require 
winter protection. When planted, a location sheltered from 
winds and midday sun should be selected, a ican ever- 
green being an admirable windbreak. In addition, as soon 
as cold weather sets in, a mulch of leaves 10-12 inches deep 
should be placed over the roots, while tall evergreen boughs 
should be stuck into the ground and bent over the tops of 
the plants. 
Native roses, as well as many of the hardy Chinese and 
Japanese kinds, need no covering, but the various hybrid 
types, such as hybrid perpetuals, hybrid teas, teas, etc., will 
not withstand our winters unless a measure of protection is 
afforded. The climbers, being largely offspring of the 
hardy Wichuraiana and multiflora types, are comparatively 
hardy except during such a severe winter as was experienced 
in 1917-18. To be reasonably sure of saving the entire 
cane growth and thus preserving the flower buds, the long 
canes should be laid down, pegged to the ground, and cov- 
