Do Prunus need heat or Light or BOTH to flower?

Here is a simple question: in preparing a tree for exhibition and you need the flowers to be open for the show, do Prunus need heat or Light or BOTH to flower?

The only answer I can give is that all the wild plums are in bloom in the woods here now, while it is still cold.

Hi Tony - I think it is an increasing day length and rising temperature hand in hand that gets a tree responding early and very, rather than a sudden increase from nothing to all. I'm playing about in the garage atm with acers - while giving plenty of light was bringing them on slowly the addition of underheating has induced new backbudding already and massively increased the leaf break from the buds. I think i will get a longer growing season and speed up ramification quite substancially. Are you trying to get a tree in flower for Swindon?

To try and best guess the exact species though look to nature - do they flower well every year regardless of the temperatures?, if so they are responding mostly to increased daylength. All our indoor controled work (plants and mostly fish breeding) was centered around increasing the lighting times, which in turn raised the temperature with the heat given off.

good luck,

Marcus

I'll tell you with my experience as an Orchard gardener that in a normal year in a way its both in that one facilitates the other.

The longer and stronger daylight hits the stems and branches and energizes the sap flow. So its heat, thats been brought on by more light. And for the sake of forcing the tree (in a good way ) your ultimate causal factor would be the heat.

This is why If I get a really warm spell that lasts a bit too long..Bang the Cherrys pop even if the temp may dip right back down again. For in that time the warm temps got the juices flowing, if you will, and it was enough to continue into flowering even though the temp plummets right back down again. The daylength remains relatively even and is ever increasing slowly, but it's the Temps that often trick my trees.

Think about when you force pussy willow cuttings as I love doing, If you just put them in a vase outside they would sit there as sticks, but when brought indoors into the warmth of your home...... they pop.
-Jay

In my endeavors in gardening, when forcing plants to flower it is light that triggers the flowering mechanisim. The plants are first grown to the size that they have flowering capability and warmth is needed to achieve this. Once they are able to flower I use a black out box to control the amount of light the plants get. Two ways to achieve this are to give only 12 hrs of light for seven days or just put the plants in blackout for 3 days in a row and flowers will pop. If you continue the 12 on 12 off the plants will continue to flower, if you return to normal day light lighting the plants will return to vegetative stage. They flower naturally after the summer solstice, the longest day of the year. When they sense the shortening days they begin to flower. Either manipulated or natural, it's the light that triggers flowering. I haven't had the need or desire to try to force any of my flowering trees, but i can't see that it would be any different. First establishing flowering capability, this may mean timing your trimming so you're not removing flowering stems, second year wood on alot of trees so if you're timming every year you may need to skip a year or trim after flowering. Then find the trigger timing, most likely 12 on 12 off, but would vary depending on when the tree flowers naturally.

RKatzin wrote: Either manipulated or natural, it's the light that triggers flowering. I haven't had the need or desire to try to force any of my flowering trees, but i can't see that it would be any different.

RKatzin,

I'm only assuming your referring to forcing plants, herbaceous perennials and the like, a Poinsettia for instance. If I'm wrong please forgive me.

The primary difference between those sorts of plants and a tree such as a Cherry in this regard, is that plants that require photo-chemical reactions to trigger flowering have tissue available, leaves and sometimes even green stem tissue, that can sense the change in daylight. A bare twigged dormant tree lacks this perceptive tissue.

Again, my pussy willow branches come inside to a dimly lit house and yet flower a few weeks later, the main variable that is altered is temperature inside my home, light actually decreases. Another great way of looking at it is to consider the Cherry blossom display in Washington DC. They flower around late March down there (I think), but Cherries don't start to flower in upstate NY until early May. We both have identical day lengths, So whats the difference between us? It must be Temperature.

With woody trees and shrubs its been my experience that warmth is what induces flowering, particularly if flowering preceeds the first foliage growth.

But it is indeed a lot of fun to force plants and bulbs by controlling dark periods.
-Jay

Yeah, that's right on Jay and I should have thought of that having often watched the orchards bloom from the bottom of the hill up. Thing is I guess is that there's just no reason to force a tree, scheduling bonsai shows for when they're in bloom is much easier, maybe?

RKatzin wrote: scheduling bonsai shows for when they're in bloom is much easier, maybe?

Agreed!
-Jay

marcus watts wrote:Are you trying to get a tree in flower for Swindon?

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