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Late season return bloom strategies for apples

Posted by Mike Biltonen 
Late season return bloom strategies for apples
August 15, 2017 05:13PM
The scenario is this: I have an organic grower that grows primarily cider fruit; old true cider apples that already have a tendency towards biennial bearing. This year several varieties set up way heavier than they should have and so return bloom could be/will be a real problem next year. Typically, a grower will thin the excess apples within 45 days of fruit set to ensure a good return bloom. These trees were thinned with Regalia and oil [which has shown good responsiveness] at bloom and petal fall. It worked with some varieties, but not so much with others. The grower didn’t have time to do much handthinning. Typically, a conventional grower could apply a synthetic growth hormone (auxin or ethylene] to trigger the fruit bud formation process. Even late in the season, like now, some effectiveness using synthetic ethylene has been shown to trigger fruit bud formation when for all intents and purposes the “sweet spot” timing was gone a long time ago.

This made me wonder about using a nutritional spray or a product with some plant growth hormones, amino acids, etc (seaweed, kelp) at this time of year and/or between greentip and ½” green next year to transform some of the undifferentiated buds to flower buds. Gibberllic acid produced by seeds is what seems to really impact flower bud formation – a GA suppressor could in fact suppress the impact of too many apples and increase flower bud formation. My theory is that shifting the hormone balance with in the tree – artificially or otherwise – would positively influence return bloom. Ditto for proper nutrition...


Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: Late season return bloom strategies for apples
August 27, 2017 08:57AM
We have been using a nutritional approach to correcting alternate bearing in our orchard and to build up our flower buds to not be as strongly affected by not enough chilling. We are using primarily products from Bioflora including Dyna-Mega, which is a naturally extracted humid acid and fish, Seaweed Creme, and a fulvic acid with trace minerals.

It has worked pretty well for the alternate bearing on some varieties, such as Newtown Pippin and Fuji, but not as well on Empire and Gravensteins. We haven't had a low chilling winter since we started the program so we can't tell about that. The thing is you can't wait until this late in the season to start, because the flower bud initiation happens right after thinning time. We combine the nutritional products in the tank with the Calcium Chloride that we are already using for bitter pit, and with Dipel sometimes. That means about 6 to 8 applications per season. We are keeping with it because we are bound to have a low chill winter in the future and it really helped on some crops after the 2014/2015 no chill winter.

Fruitilicious Farm
Zone 9b in California
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