Should I defoliate these acer palmatum seigens?

toolpro

I received two acer palmatum seigens yesterday, 2-3 years old, almost bare-root, in excellent condition. The problem is that the temperature rose to 91F and will hover there for the next week, here in Atlanta, GA. This is not a good time to be disturbing these trees, but I had no choice since they were almost bare-root. I potted them in a grow mix, and have them in the garage, which is the coolest place I have.

Should I defoliate? Partial defoliate? Any other advice?

Thank you,
Rick

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TimZ8

Do not defoliate. They have been stressed enough. The use of defoliating is much over rated in my opinion and should only be used for mature trees. I lost a maple last year due to defoliating. You are taking a big chance using the technique. Trees will only take so much abuse. If there is already two stikes against the tree it can be the third strike and your out.

bisjoe

When you repot at that kind of temperature there's a lot of transpiration, loss of moisture through the leaves until the roots settle in. I suggest misting it 2-3 times a day (leaves AND trunk/branches) to help it out for a few weeks. Also, don't fertilize until it recovers.

toolpro

Got it.
No defoliate.
Mist every chance.
No fertilizer.

What do you think about leaving them in the garage for a couple of weeks? There are some windows, so it is not totally dark. And it is at least 10 degrees cooler than outside in the shade.

Thanks guys,

Rick

Joanie

Can you make them a shade area outside? Our eyes adjust to the dark, but trees need the wavelengths that we don't/can't see. If they have leaves, they probably need more light than your garage has.

My guess is that it isn't the heat, per se, it's the amount of sunlight. It could be 100 degrees and humid, and as long as the leaves aren't in a full strong sunlight, they will be all right. Now, that's just a guess, and others may chime in to agree or disagree.

As Al said on a different thread, shade cloth diffuses sunlight. It doesn't really block it as much as it spreads and diffuses it. Dappled shade under a large existing tree is also a possibility. Surely in Georgia there is a nice dapply tree that would keep them shaded but in the outdoors?

Joanie

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Repotter

Joanie is right about not keeping them in the garage, too little light.
They need the light to make food through photosynthesis.
A shade spot would be ideal.
I kept my Trident Maples under shade cloth when I lived in Florida and they did great after repotting too.

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toolpro

I thought that once the temperature got beyond the mid-80s, acer palmatums were stressed by the temperature. I don't recall where I got this notion that high temps are such a problem.

Does anyone know definitively the effect of high temps on these trees?

Thank you very much for your attention,
Rick

Moleque_san

Summer Temps are stressful on most if not all trees. There are trees that love the sun and continue to do well during the summer but you still need to take precaution and watch the soil and leaves. Keeping your trees outside is the Best thing you can do and only bring em to a garage with UV lamps if winter gets too cold. Also, all trees need UV for photosynthesis, cool thing about that is you dont need to be in full sun to get that.

Maples are delicate and require shade/dappled shade. They cant handle the harshness of Full sun or high strength winds, it will burn the leaves and sweat the tree too fast for it to reproduce energy. Shade temps are significantly lower then full sun temps and is more to its natural habitat for maples.

any other chimers?

Brent

It's pointless to talk about maximum temperatures for woody plants without also considering the humidity. Japanese maple, Acer palmatum foliage can burn from excessive transpiration even in the high 80's F in strong dry winds. On the other hand, I start cuttings of them in the greenhouse with the humidity at 80 to 90% with the daytime temperature held at 95F and above. I don't start seeing defoliation on the cuttings until it gets higher than about 102F. Below this temperature, they are as happy as clams, and they don't even have a root system.

So, the solution is to treat them as cuttings. Give them 50% shade, perferably with shade cloth to avoid any direct sunlight. Next, loosely tent with with poly, but allow some air circulation, mist under the tent when it starts to get dry. Keep them OUTSIDE, unless you have a greehouse.

An even more bizarre examples: I helped my neighbor start some grape cuttings one year in his greenhouse. On one of the hottest days of the summer (of course) the power goes off and we have to ventilation and no mist. His helper comes running to me and asks me if he should throw open the doors to cool it off. I tell him absolutely not! As long as the greenhouse is closed, the humidity stays very high. The power was off for a couple hours. Later, I read the max/min thermometer. It got up to 135F, but very few of the plants were damaged.

Brent
EvergreenGardenworks.com
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