132 MISSOURI BOTANICAL GARDEN BULLETIN 
erings remain, even though growth is starting, until the 
danger of heavy freezing is over. Winter usually makes one 
concerted effort to remain, in the latter part of March or the 
beginning of April, and it is this spell that must be guarded 
against. It is advisable to remove the coverings gradually, 
so that if unseasonable weather comes the plants will not be 
entirely unprotected. 
SMOKE INJURY TO ROSES 
Roses can be protected against frost damage by some kind 
of covering, but there is no known protection against smoke 
injury. All plant life suffers in a smoky atmosphere, some 
plants being more susceptible than others. Roses suffer from 
the periods of smoky atmosphere, but it is difficult to de- 
scribe the injury. While the damage is not immediately 
noticeable, the vitality of the plants is gradually lowered. 
Certain roses simply will not grow. They may remain alive 
for a few years without making much growth and then fin- 
ally succumb. Examples of this are the Persian and Harri- 
son’s yellow roses planted in the Garden a few years ago, 
which threw up a number of shoots the first season, blos- 
somed the second season, but made no new growth and then 
died during the third year. In the county these grow read- 
ily. The much-heralded Hugonis rose remains at a stand- 
still from year to year. Plants six years old have grown 
about four feet and new canes attain about the same height. 
A few flowers appear every spring, but never do the plants 
bloom as profusely as the nurserymen and growers claim for 
Hugonis in other places. Wonderful examples of this plant 
have been seen elsewhere, but from the experiences up to 
this time it cannot be recommended for smoky localities. 
The baby rambler roses are not growing as well as a few 
years ago, but are still among our best. The rugosa roses 
grow vigorously from year to year and apparently the smoke 
has little effect on them. Most of the hybrid perpetuals still 
are doing splendidly, although Captain Christy has not been 
thriving. The sweetbrier roses grow rampantly, are ex- 
tremely hardy and require much room to spread, but unfor- 
