NovVEMBER, 1915.] THE ORCHID REVIEW. 331 
By W. H. WHITE, for many years Orchid Grower to the 
late Sir Trevor Lawrence, Bart., K.C.V.O. 
F CALENDAR OF OPERATIONS FOR NOVEMBER. y 
OVEMBER is generally considered the: period at which the winter 
treatment of Orchids should commence, and during this time it is 
necessary to afford careful study in everything appertaining to the future 
welfare of the plants. The great difficulty is to balance the four great 
agents ruling plant life—light, heat, moisture, and air—so that those 
Orchids which are at rest are not unduly excited to start prematurely, 
and that those growing may be encouraged to mature sound healthy 
growth. Natural light being beyond our control, while heat, moisture, 
and air are not, it follows that we must use the three in proportion to what 
we get of the other. Thus during the winter months the temperature of 
the various houses on light bright days should be a few degrees higher than 
on dull heavy days, and on every day the highest temperature of any house 
should be between the hours of twelve and two, while the lowest should be 
during the hours of darkness. The difference between these two extremes 
should be from five to ten degrees when the temperature is maintained by 
fire-heat, and several degrees higher may be allowed during sunshine. 
And, as mentioned in a former Calendar, sudden fluctuations of temper- 
atures should be avoided as much as possible, for many tender Orchids 
under cultivation are easily injured thereby. These are important matters, 
but difficult of accomplishment at times, owing to our changeable weather, 
and the error is quite as often in having too much heat in the pipes as in 
having too little. 
These remarks should be remembered by the young beginner, for with 
a range of ten degrees between the two extremes of the winter temperature 
the plants generally should be quite safe. The following temperatures 
should be aimed at: East Indian house, 60° to 70°; Cattleya house, 
55° to 60°; Mexican and Intermediate houses, 50° to 60°; Cool house, 
45° to 55°. Any of these divisions might fall a degree or two lower for a 
short period, at times when, through very severe frost, much fire-heat is In 
use, causing the atmosphere of the houses to be more than ordinarily dry. 
Undoubtedly, for the next few months to come, the heating apparatus will 
have to afford most of the warmth in the various houses, and should be used 
carefully, as an excess of fire-heat, if persisted in for long together, is 
frequently the cause of injury to the plants, and of the increase of insect 
Pests, particularly thrips and red spider. Cockroaches also multiply very 
quickly when much fire-heat is being used, and Orchid-growers know only 
too well the injury these voracious pests do to the succulent roots, flower 
Spikes, and tender growths of the plants. 
