C TA^PTER 6 



BREAKING THE REST PERIOD OF PLANTS 



The object of greenhouse culture is to grow cer- 

 tain crops or blooms at a time and season when 

 these cannot be produced outdoors. All plants un- 

 dergo a period of rest. Bulbs, for instance, enter 

 their resting state when the leaves all die. No mat- 

 ter how cold, warm or wet, bulbs will not grow 

 again before the fall. Howard^ has found that it is 

 very difficult to shorten this dormant period, at least 

 during the earlier phases of the rest. He further 

 found that of all treatments, drying, followed by 

 injection with ether and Knop's solution (made up 

 as follows: Calcium nitrate i gr., magnesium sul- 

 phate 25 gr., acid potassium phosphate 25 gr., and 

 water 1 liter.), and combinations of these were most 

 effective in shortening the rest period of bulbs. The 

 injection may be accomplished by piercing the bulb 

 with a hypodermic needle. Herbaceous perennials, 

 too, like the bulbs, undergo a rest period. Frost, 

 drying, and ether appear to be the most effective 

 agents in breaking this rest period. To treat plants 

 with ether, a galvanized iron chamber is preferred. 

 The latter as used by Howard is shaped like a cylin- 



* Howard, W. L,, Missouri Agr. Expt. Sta., Research Bui. 15: 

 3-25, 1915. 



86 



