Manipulating female flower intensity in ‘Yu Her Pau’ Litchi by delayed winter pruning

'Yu Her Pau’ litchi (Litchi chinensis) has excellent fruit quality. However, its production on Taiwan is limited by low productivity despite being regarded as a high-quality fruit. It is known that litchi’s leaves play a critical role in floral induction under low temperature. Thus, we hypothesized that the flower intensity in spring could be manipulated by altering the leaf quality in winter, thereby increasing crop load. In this pilot study, ‘Yu Her Pau’ trees were pruned in mid-December [early pruning (EP)], one of the common cultural practices carried out by growers in the region, as control or mid-January [late pruning (LP)]. This resulted in 50% and 100% canopy foliage for EP and LP trees, respectively, between mid-December and mid-January. At the peak blooming time in March, LP trees produced significantly more female flowers than EP trees (95.8 and 56.1/panicle, respectively) with no negative effects on initial fruit set number, fruitlet abscission, or fruit quality at harvest. Our results suggest additional mature leaves present on trees in mid-December onward may benefit litchi flower formation without affecting fruit retention. Thus, preserving leaves with delayed pruning might potentially mitigate the negative impacts of warmer winters due to climate change on litchi flowering.