Published online by Cambridge University Press: 27 March 2009
A statistical experiment was made on May King lettuce grown in a gravel soil in the unheated greenhouse to ascertain the effect of periodic sowings, two levels of water, and alternate drought and saturation with water on bolting and growth.
Mature lettuces at a low level of water were darker than those at a high level. The total numbers bolting irrespective of treatment were highest in May to July, and this period coincided with temperatures above 60° F., long days, and decreasing ages from germination to bolting; the largest lettuces were harvested in October to May (excluding mid-January to late March), a period of low temperatures less than 60° F., short days, and increasing ages from germination to harvest.