Flowering and fruit set in lychee (Litchi chinensis Sonn.) in subtropical Queensland

Abstract

The pattern of panicle and flower development of lychee (Litchi chinensis Sonn.) trees was studied in subtropical Queensland (lat. 27¦S.). The cultivars studied were Tai So at 3 sites, Bengal at 4 sites, Kwai May Pink at 2 sites, Salathiel at 3 sites, and Wai Chee at 2 sites. Tai So was the earliest cultivar, with panicle emergence in late May and flower anthesis in mid September. The other cultivars were 5-7 weeks later. Tai So had a longer period of flower anthesis than the other cultivars (4 weeks v. 1-3 weeks). Cultivars Tai So and Bengal generally had longer panicles than cvv. Kwai May Pink, Salathiel and Wai Chee (17-32 v. 10-14 cm), and more flowers per panicle (1800-3400 v. 400-900). Similarly, the number of fruit per panicle ranged from 7-33/panicle 2-3 weeks after the end of flowering, to 4-22/panicle at harvest. The proportion of female flowers setting fruit ranged from 2.1 to 19.5%. Similar estimates for fruit carried to harvest ranged from 0.8 to 6.8%. Variations in the times of panicle emergence, panicle development, and anthesis among the cultivars in relation to seasonal progressions in temperature affected the number of fruit set. The number of fruit set per panicle increased as the number of female flowers per panicle increased. Higher numbers of female flowers were associated with maximum temperatures during flower development of 18¦C, with lower numbers at 23¦C. Higher maximum temperatures during anthesis (30¦C v. 24¦C) increased the proportion of female flowers setting fruit.