I understand that once a tree/shrub has reached maturity, flower buds are apical buds that have morphed from vegetative ones. Yet, not every apical bud morphs into being a flower bud and that fraction that do seems to vary – why?

I’d like to know how I can maximize the flower buds on my flowering trees, rhododendrons, and the like. Conversely, I’d like to know how to suppress flower buds forming. In bonsai practice, for example, it is believed that flower buds ‘waste energy’ that could otherwise go into vegetative growth. Once the bonsai is developed, however, flowers are highly prized.

What are the factors that anyone might control to turn on/off formation of flower buds?

  • Do you have a species in mind? – Grady Player Jan 6 '16 at 4:44
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    I am interested mostly in general principles, but let me say rhododendron (including azaleas), prunus, malus, pyrus, and quince. I am not interested specifically in lilacs, for example. On the other hand I welcome any insights that might be known from the study of any particular woody species. – Jim Young Jan 6 '16 at 5:11
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    I only ask because they may use different triggers to determine flower set, azaleas may use light duration, lilacs may use ratio light/dark, and prunus may use temperature... They are all tropisms and not universal in all angiosperms – Grady Player Jan 6 '16 at 5:13

It's not quite as simple as you state in your question, but then it never is, with plants. Take rhododendron, for instance - it needs chilling for a certain length of time in order to produce flowers, whereas azalea type rhododendrons don't necessarily, depending on the variety. Equally, a shortage of water when flower buds are being initiated or forming means the incipient flowers will abort, and given that initiation varies between species and varieties, it's never that clear cut. So, the other two main factors involved in flowering at all, never mind prolifically, are water and temperature - and that requirement varies between plants. Third is availability of nutrients - some plants flower better if certain nutrients are freely available, others flower better on poorer soil and in poorer conditions.

What you can do with the plants you wish to produce a large number of flowers is to research each one in particular, and provide the optimum conditions for the plant generally - a contented plant will flower well, unless some infection or infestation occurs which affects either the plant itself or the flowers.

As for preventing flowering, the only way I know is to nip off flower buds or obvious flowering growth when they form, but then I'm not a bonsai specialist - there may be some other method they use.

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