May 28, 2016
I have a number of decidious fruit trees in my home orchard that don't seem to want to drop all their leaves in winter. I live in Central Florida zone 9b. Because of my lattitude during winter we get fewer hours of daylight than in summer but the difference is not all that much. I know that in the northern lattitudes there is a significant difference in the number of daylight hours between summer and winter. I also *believe* that is the differing (lower) levels of daylight hours that causes decidious trees to drop their leaves in winter and enter dormancy. In the past I have manually defoliated my decidious trees sometime around mid December. This year we are almost in late December and I am trying to decide if I should defoliate them manually or just allow them to decide for themselves when they want to drop their leaves and enter dormancy. Can you folks who live in the higher lattitudes tell me if you experience the same problems with your decidious fruit trees? At the higher lattitudes I would guess that the trees would quickly drop their leaves in early winter and enter dormancy right? If you also experience problems with some of your trees not wanting to enter dormancy on their own can you tell me how you deal with the situation? Do you defoliate them manually for use some other technique to get them to enter dormancy? Or do you just leave them alone and let them decide when and indeed if they ever want to enter dormancy?
March 16, 2015
Deciduous fruit trees require differing amounts of ‘chilling hours,’ usually sustained temperatures below 55 degrees, with temps over 60 beginning to reawaken them. I’m in SW Virginia @ 2,400 feet, and the apple leaves finally ‘blew off’ around a week ago. Other leaves such as plums, persimmons and pears were gone a month ago. I believe length of day triggers the return of plant sugars to the roots, leaving the yellow-orange pigment in the leaves, and have assumed it takes a hard freeze or harsh wind to cause them to drop.
I’ve read that a limitation on successful deciduous fruit trees in southern latitudes is the lack of chilling hours, or winter rest & rejuvenation. The nation of Israel has bread several apple varieties requiring fewer chilling hours for this reason. I'll assume your orchard planting is relatively new.
It would likely be our smattering of our California members, or one time contributors who could best relate to a zone 9b. I’m at 6b, and this is the first I’ve heard of actually hand-removing leaves to force a tree into dormancy. It’s still early winter, and we’re again due for some more (we had a low of 13 degrees a couple weeks ago) ..colder weather this coming week...
May 28, 2016
I am aware of the chill hours requirement for deciduous fruit trees. I currently have low chill apples like Anna, Dorsett Golden, and Tropic Sweet but I also have pears like the southern Bartlett, Kieffer, Hood, Flordahome, and Bladwin. I also have plums like Santa Rosa, Methley, Shiro, Starking delicious, and Apricots like Blenheim and Aprium. I also have Fuji, Braeburn, Cripps Pink, Gala, and Golden Delicious apples. All of these trees have dropped more than half of their leaves. But some leaves near the top/end of the branches just hang on tenaciously. I guess i was wondering if others see the same things in their orchard. I think you are right though that it would be a more meaningful comparison if i could get feedback from our friends in California who also live in zone 9b. Dave Wilson nursery and Kuffel Creek nursey in California do recommend manual defoliation to induce dormancy. But i wonder if the tree will eventually adapt to its new climate if i just left it alone.
March 16, 2015
That’s an impressive lineup, you’ve obviously done your homework! As mentioned, I had ‘yellowed leaves’ hanging in my apple trees (and those of a neighbors) until recently. But “manual defoliation to induce dormancy,” news to me!
My concern with late leaf drop, even back in Oregon was that of an early wet snow. The snow gloms onto the surface of the leaves and can take branches down, especially with a silver thaw, or freezing rain. I doubt you’re inline for any of that.. but if you’re in line to receive any of the 45 mph wind gusts we’re supposed to get ‘tonight’ (SW VA) ...that may take care of them! Otherwise I suspect they’ll do fine
March 25, 2015
In this report by a profound botanist in Russia Ilya Kotovich, whom one can read to easily know what had been supposedly unseen before, that there can be pretty good activity going on inside young tree branches all times of the year. Due to thin semi-transparent bark thin enough to react with light, they are still active there beating the drums.
View the 46% to midway down subset of this link where it regards summer anthocyan production from light through new bark, in itself in the aid of protecting damage from sun, even December in order to aid almost anywhere it is really cold.
So it is my opinion there are always means to track light from the outside for other purposes such as photoperiodic preparation to flowering, which in itself is to say even before (ie. December) the dormant buds would start to be pushing.
On the other hand leaves can harbor disease and infect branches. In some cases and locations it is very important the leaves fall in a proper time. I don't know about Florida but it could leed into an infection if it happens all at once into the branches and a big problem then.
August 3, 2015
The persistent leaves caseroj describes may be a product of juvenility, a common trait of many plants.
My quince tree in zone 8b lost all mature leaves over a month ago, but several hundred immature leaves remain at the ends of new-growth whips, and many will still be there when I prune next month. This season the temperature has not gone below +29F yet.
March 25, 2015
May 28, 2016
"The persistent leaves caseroj describes may be a product of juvenility, a common trait of many plants."
Yes I can confirm that in fact the leaves which were holding on were mostly on the new growth tips. Either way I went ahead today and manually defoliated my apples, pears, peaches, and apricots. I left my plums alone just as an experiment to see what they do on their own as the winter season progresses. Here in central Florida we don't start to get really cold (relatively speaking) nighttime temperatures until January. I am using the plums as a control set to see if as the temperatures start to drop significantly whether they will respond and finish casting off the existing leaves. Coincidentally I also own two persimmon trees. One is a Tanenashi (astringent) and the other is a Jiro (non-astringent). Those two are behaving just like I would expect them to. Their leaves have turned orange-yellow and are starting to drop en masse. earlier this year I placed an order for some heirloom apples and a Fuyu Persimmon from *Trees of Antiquity*. I will be receiving from them among other things two Hudsons Golden Gem rusetted apples, two warren pears and a Fuyu persimmon. I am really excited about the Fuyu because it has been hard to find this tree locally. Part of the reason I decided to defoliate the trees manually was to avoid the old leaves passing on any fungi to the new leaves. I plan to spray with a copper fungicide before they break dormancy next year and it seems better to do that without any leaves. By the way....look at the background image of the apples and leaves that HOS displays on this page. Can you tell me if those brown spots on the apple leaves are normal? My apple trees started to develop this sympton this year. It happened when I brought to Granny Smith apple trees into the orchard form an online retailer that had the same spots on their leaves. It seems to have spread to all my apple trees before I got a chance to uproot and remove those granny smiths from the orchard. Is that what they call cedar apple rust? Would a copper based fungicide be effective against it? If so is it like peach leaf curl in that it needs to be applied *before* the new leaves come out?
March 25, 2015
To me HOS image is showing apple scab on leaves, which to my understanding is more a cosmetic concern on the fruit. Anyone with more apple tree growing experience may still correct me on it.
The extent of how much damage that can move along from dead leaves and into the tree through developing buds (as others have so indicated) still rests on how well suited the name of your variety does in your area. Maybe other people that live closer to you can chime in before too long or as Viron said from California.
What I was referring to as far as my last post yesterday is recognition that plants are smart. They probably have a so far invisible tactic in this case of recovering from adult flowering mode wood back into a juvenile wood, in itself we recognize juvenile as the ability to learn from conditions or changes made in the outside environment as a plastic plant. For example the fast evolution of bacteria that cause problems that plants develop while juvenile the scientific term "plant plasticity" is the term used for an evolutionary model to explain the invisible adaption of plants to other devices or critters. Other changes directly related to tree health that are severe enough have already been established while green were photoperiod prediction models for a plant to winter dress, flower, etc, that have less to due with future seed)
If epiginetics were true (which it is), then plasticity would be about the same thing if the said 'apple tree problem' passes a helper (ie. cheat sheet) to the future seeds it produces.
Now to your decision, if you were to defoliate, "yes" it is likely it can help the apple tree already mature to live a bit longer if performing the operation during dry weather instead of moist, in order that the new openings have a couple days dry weather to wall or heal against infection.
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