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Grittyville, WA

A lot of things coming together in my mind, so bear with me. Auxins help produce ethylene. In trees you are going to have your best fruit on the youngest branches with the largest buds, but trees have a nearly infinite reserve of resources compared to an annual like a pumpkin plant. With a pumpkin plant, a good set (fruit) on large new growth is a good start, but it’s not everything. Both the tree and the pumpkin plant have some mechanisms where it’s unsure if it wants to fully invest in one single fruit. Apical dominance produces ethylene, which has a positive affect on fruit size, it the plants way of saying this “might be” a good place to set a large fruit... but the apical dominance also says that the apex itself is important, at least equally important as the fruit, if not more so. So the plant may nevertheless divert significant resources from the fruit to the apical growth.

1/28/2019 7:50:48 AM

Grittyville, WA

Both an annual (pumpkin plant) and a perennial (fruit tree) want to make good decisions about where to invest resources. A fruit tree wants to set fruit in areas where it feels safe from competition. If there is a lack of light, somewhere, but plenty of resources, then rather than set fruit, it gets hyper competitive and send fast growing suckers in attempt to dominate and win vegetatively. It has a long term (multi year) survival plan. So you prune evenly up and down the tree so that “phloem fruit sinks” are spaced evenly everywhere up and down the trunk and there is light everywhere and healthy new growth everywhere. The result is you don’t get large suckers and you get lots of good sized fruit. But then how do you prune a pumpkin plant? It’s designed to distribute its effort based on an annual production regimen. You don’t have “2 year wood” and you can’t prune apical buds willy nilly the way the orchardists can. There is no energy reserve coming from elsewhere to make up for excessive pruning.

1/28/2019 8:16:54 AM

Grittyville, WA

The meat of my thinking is, what if a guy like Steve Daletas, who extensively covers his vine tips (shades them) is getting the best of all worlds, perhaps entirely on accident? What if (possibly unintentionally) you allow good amounts of light to your vine tips in June, so you get the maximum amount of ethylene into the blossom, but then when summer really starts, shortly or immediately after the blossom has set, you shade all the vine tips.

Here is a speculation: This causes a decrease in the apical dominance of the tips, which of done earlier, would result in a lower quality fruit set. But if this is done a few days after the fruit has set (as the window for a benefit from ethylene closes) then you get the best of all three worlds.

1) natural ethylene for a better fruit set
2) reduced apical dominance for better fruit growth, and dominance
3) you don’t actually have to remove any of the vine tips, so your phloem “source” can continue to expand... the reduction in light reduces dominance chemically but does not actually stop growth.

Let me know what you think!

1/28/2019 8:34:37 AM

Grittyville, WA

I’m not saying Steve does not know what he is doing. He has a method he sticks with that works. He knows his method works. I’m just speculating about why.

1/28/2019 8:41:15 AM

Grittyville, WA

Other top growers use this method too but I’m using Steve as an example because I remember his efforts and diligence in covering vine tips from a club presentation, plus his consistentently good results, and his climate is in some ways similar to mine... so altogether I can speculate more knowledgeably about his methods. But this speculation about vine tip shading could apply to anyone.

1/28/2019 9:18:29 AM

Bethlehem CT

Interesting thoughts, Glen.

1/28/2019 9:23:12 AM