Annual leaf drop time and rootstock

General Gardening
#1

Hello,

After a few years of knowing this great forum, this is my first thread.

I have a question where I can’t really seem to find an answer for out of the experience.
Of course there are a lot of factors which makes the tree decide it is time for the annual leaf drop.

But I came to think of this when I saw some of my Cercis canadensis. Some have already dropped all their leaves, some not at all and a lot of them are in between.
Now my question is, does the rootstock and its genetics determine the leaf drop or does the grafted part? Or is it somewhere in between?
Also, I read that some people do believe that earlier leaf drop means better cold hardiness? Has somebody experienced that?

Thanks for the knowledge.
Sincerely
Randy

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#2

Those are all good questions!

I see this with some of my shade trees, and the only clue I have is that the healthier trees drop before the unhealthy ones, which tend to cling to their leaves

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#3

My maples and pear trees have dropped their leaves, but my apple is still hanging on to a fair percentage. I can’t say the apple is not healthy, but maybe it’s telling me something?

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#4

Thank you, Mark and Itilton for your input.

Itilton as for the shade trees, could that maybe be because of the dappling of the shade? Here trees that are closer to streetlights are a few days or even a week behind other trees in dropping of their leaves.

I specifically mean in the same species. I know genetic differences in tree individuals from seed also could determine the time when the tree has had enough environmental changes that trigger it to go into dormancy and thus drop leaves. But even between clones, the location could differ, and thus the environmental input, or indeed stress could make it go to dormancy earlier or cling on to leaves.

Casus: Cercis canadensis ‘lavender twist’ is grafted on a few Cercis seedlings.
‘Lavender twist’ his dormancy trigger should always be the same(not thinking about environmental input). But the seedlings are individuals and the dormancy time could differ.
Does the rootstock determine the dormancy trigger? It at least has control over it.
Does ‘lavender twist’ determine the dormancy trigger?
Or would it somewhat bang in the middle?

Thanks for thinking with me!

#5

I have several of the same variety plums ( of both European and Japanese ) in different locations. The plums located in the lowest elevation have already dropped their leaves, while the plums in the slightly higher elevation ( difference of 8-10 ft created by a low valley with stream nearby) still have all of their leaves. Another thing to note is that the plums which dropped their leaves already were more significantly impacted with shot hole fungus.

#6

I don’t know the answers. I do know I have a wild crabapple that I have grafted one limb over to Jonsib crab. The wild portion’s leaves are yellowing/dropping off while the Jonsib leaves are still green and hanging on for the most part.

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#7

That 10 ft could probably make a significant difference because the light intensity is higher because of the elevation I guess? But I do see a lot of diseased cherry’s in the neighbourhood, all the trees affected in Summer have lost their leaves two/three weeks already.

#8

Same experience here. My wild crab trees have all dropped leaves, but 90% of grafts onto those wild crabs are still green and holding.

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#9

@Randy

Trees in general speak to me but in their own language. Pear trees are deciduous so they might just be telling me it’s winter when they lose their leaves. So why don’t they all do the same thing? Are all people the same? Rootstock or scion influencing leaf drop? you asked and the answer as you expected is both. There is more at play here so I found an article to back me up on this Do Pear Trees Lose Their Leaves? 5 Key Causes & Preventions – Thriving Yard

" Here are the five main reasons why pear trees lose their leaves (aside from autumn):

  1. Poor Soil Conditions
  2. Pests
  3. Diseases
  4. Dormancy Complications
  5. Human Interference"

Trees are like people don’t try a one size fits all approach but many do. Learn to look at the tree and see what it needs with a glance. @fruitnut is one of the best tree guys there is when it comes to reading what the tree is saying. There is always more we can learn.

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#10

my apples / cane fruit are always the last to drop leaves here. mine are still on right now even after several killing frosts. even found a few red raspberries still on the plant.

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#11

I’m waiting for my nects to drop so I can do a copper spray, but they’re still still green.

#12

With my apple trees the rootstock doesn’t seem to be the determining factor for leaf drop. I have a number of trees with a different variety grafted on where the main tree has dropped its leaves but the grafted branched hasn’t, and visa-versa (this is mid Nov). Out of curiosity I made a list of the dropped vs still on varieties, wondering if later ripening/winter varieties might hold leaves longer. It’s possible it might have something to do with it as my trees still with leaves (mostly brown and getting thin now) include these winter varieties: Prairie Spy, Starkey, Black Oxford and Honeycrisp. Haralson is about half way between keeping/dropping leaves. But Canadian Strawberry also holds its leaves late and is a Fall variety.

I don’t see any difference in hardiness between those who drop early and those who keep hold of their leaves, having older healthy trees in both camps.

Interesting to consider the whys and wherefores! Sue

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