Variation in the Onset of Flowering of Summer Squash as a Function of Days and Heat Units

Abstract

The time from sowing to flowering and maturity of summer squash (Cucurbita pepo L.) varies depending on environment. Research was conducted over a 2-year period to assess flowering time of five squash cultivars grown at different locations and times in Georgia representing varying thermal regimes. Heat units (HUs) were calculated using a single equation to determine if this approach could account for a significant proportion of the variability in the time to onset of flowering observed over this range of environments. Depending on the cultivar and flower sex, the number of days to flowering varied as much as 20 days. There were no cultivar differences in overall mean days to first staminate flower; however, there were differences in mean days to first pistillate flower. There were cultivar differences in HUs required for staminate and pistillate flowers. The use of HUs significantly affected the variability in time to flowering as indicated by regression analyses and mean absolute differences between predicted and observed days to flowering.