Apple flower bud development and return bloom – video

November 2024 | Presented by Dr Poliana Francescatto | Future Orchards® video presentation

Flower bud development in apple is closely connected to crop-load management and the following season’s return bloom. Poliana Francescatto explains the developmental sequence from flower induction and initiation through differentiation and anthesis, and shows that the timing of flower initiation differs substantially among cultivars.

The presentation highlights that varieties prone to biennial bearing initiate flowers earlier than more regular-bearing cultivars. Examples include earlier flower-initiation peaks in Honeycrisp and Fuji compared with Gala. Crop load is one of the major indirect factors affecting flower formation, alongside rootstock, pruning and light, irrigation, nutrition, girdling, climate and the use of plant growth regulators.

Trial results presented for Honeycrisp and Fuji demonstrate the importance of thinning timing. Early reduction of crop load produced stronger return bloom than leaving excess fruit or waiting until later fruitlet stages. Francescatto’s key message is that flower formation occurs during the previous season while the crop is still developing, so return bloom is already being influenced well before harvest.

Plant growth regulators can support return bloom, but the presentation cautions that summer PGR programs work best when crop load has already been reduced early. Early thinning remains the primary strategy for securing regular flowering and reducing biennial bearing risk.