Flower buds for next year's crop

It's that time of year again - your apple trees have been busy setting terminal buds on this year's extension growth, at the same time as they are getting ready for next year's crop. The annual process to initiate flower buds is now underway, which is the critical first step for a successful crop next year.

Usually trees are initiating flower buds at the same time as they are dividing and filling cells in the fruit, and moving storage carbohydrates to the roots as the beginning of the hardening off process. While some trees are not carrying much crop this year, there is still a high energy demand on them. This is why we encouraged all growers to maintain good tree health by adequately managing pests, weeds and irrigation where necessary.

Flower bud initiation is just the first step in a long and complicated process that results in a complex flower structure opening next spring, ready for pollination. With high power microscopes, plant physiologists have photographed tiny groups of cells that look like tiny volcanoes growing on fruit spurs (Figure 1). The differentiation process continues each week, and advances in tissue development can be observed through a microscope. The king bloom can usually been seen by the end of August, and all the secondary flowers by the end of September. The bud scales form shortly after that and the bud prepares for winter.

It is a truly amazing process that is not yet fully understood. Of special interest is what makes the process begin (or in the case of biennial bearing, what stops the process from beginning). Researchers are studying plant hormones, especially from the developing seeds, but more remains to be learned. For now, just appreciate what your trees are doing now, and look forward to a new crop of blooms next spring.

Figure 1. Five-leaf primordial in a differentiated apple bud.

Figure 1. Five-leaf primordial in a differentiated apple bud.

For more information:
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E-mail: ag.info.omafra@ontario.ca