Foliar boron timing

General Fruit Growing
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How late is too late to save this year’s baby stone fruit with a boron spray? (Minnesota 4b)

We have experienced complete fruit drop several years without foliar boron. (There’s plenty of B in the soil, but pH is too high so it’s inaccessible.)

A couple of years, we’ve managed to get a couple of boron sprays on during blossom and shortly after, and got decent crops of plums and apricots.

I know this is the crucial moment, but due to family/job reasons, i can’t be there to get the spray on right now - we’re at petal fall.

If it waits another week, will we lose the crop?

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If you have foliage to absorb it perhaps not too late, when I saw your post, I read this article that seems informative:
“ Yes, boron sprays can help improve fruit set in many plant species, particularly under specific conditions. Boron is a crucial micronutrient that plays a vital role in pollen germination, pollen tube growth, and cell division, all of which are essential for successful fertilization and fruit development.

Here’s a more detailed explanation:

  • Boron’s Role in Fruit Set:

Boron is involved in various processes that lead to fruit set, including pollen germination and tube growth, which are necessary for fertilization. It also helps regulate cell division, which is important for the development of the fruit.

  • Foliar Sprays for Boron Deficiency:

When boron is deficient, especially during critical periods like flowering and early fruit set, foliar sprays can be an effective way to quickly provide the plant with the necessary boron.

  • Factors Affecting Boron’s Effectiveness:

The effectiveness of boron sprays can depend on various factors, including the plant species, growing conditions, and timing of application.

  • Examples of Boron’s Benefits:

Studies have shown that boron foliar sprays can improve fruit set in various crops, including apples, pears, avocados, and tomatoes. For example, [The Almond Doctor] reports that post-harvest boron sprays have been shown to increase fruit set and yields in almond orchards.

  • Boron and Yield:

Boron sprays can also contribute to increased yields by improving fruit set, which can lead to a greater number of fruits per plant.

  • Application Timing:

[Yara UK] suggests that applying boron in the autumn, two to three weeks before leaf-fall, can be particularly beneficial, as the boron becomes available to encourage better flowering and fruit set in the following spring.”
So I’m thinking it might be better applied in fall 2-3 weeks before leaf fall!
I plan to spray twice a year, once in fall and as soon as I have leaf buds opening in spring. Perhaps someone with more experience will comment, I look forward to seeing what others have learned.
Dennis
Kent, Wa

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Boron is a critical microntrient but a little goes a long way. I was able to eliminate my problemss