Root Care

vln1502

I live in flyover country and am in AHS Heat Zone 7. It seems like my trees really suffered this summer from the intense heat. Does anyone have a method for keeping roots cool during extreme heat? I don't really have any shade to speak of and most of my trees are still in plastic pots, so the sun really bakes them in July and August.

Thanks,

Vic

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Vance Wood

I think everyone had this problem this summer. It started out hot and did not really moderate much until September. Hot pots make for stressed out trees. You really cannot water enough to make up for this problem without creating more and even worse problems. The solution is to move the trees into locations where the posts are not in full sun during the heat of the day and or mulch the pots to keep them cool.

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The only finished bonsai is a dead one; me 1992 MABA Des Moines Iowa

vln1502

Thanks, Vance, but that makes me ask: Wouldn't a heavy mulch heat up also? What about suffocating the roots because youv'e cut off the air circulation?

Vic

Dav4

The mulch, being in contact with the ground, would essentially maintain the same temperature as the ground. In other words, it wouldn't heat up much. As far as air circulation, I would think mulch has much more air in it, due to its large chunky nature, then say regular garden soil, which still has plenty enough oxygen for trees growing in your yard. Again, no worries. I've heard some folks will use old white t- shirts or sheets to wrap their pots with during the heat of the summer- white reflects heat. Others, particularly in the south or west, use shade cloth tents to protect the trees from intense summer sun.

Dave

rockm

I simply wet old white or light colored T-shirts and spread them over the pots on the benches during the day. This keeps the pots surprisingly well cooled and allows the trees to be left on the benches.

vln1502

Yeah, seems like I remember the term "evaporative cooling" from somewhere.....the wet cloth would cool the air passing through the fabric by about 10 degrees or so.


Thanks.

Vance Wood

If you mulch with bark chips or coarse bark it will cool as the water evaporates out of it.

__________________
The only finished bonsai is a dead one; me 1992 MABA Des Moines Iowa

rockm

"Yeah, seems like I remember the term "evaporative cooling" from somewhere.....the wet cloth would cool the air passing through the fabric by about 10 degrees or so"

Evaporative cooling is only part of the story. The light color cloth reflects sunlight and shades the pot. The pots underneath the T-shirt (or towel)covering stay 20-25 degrees cooler than a pot left in the open sunlight. Where some pots got too hot to touch in the August sun here in Va., the covering makes them cool to the touch.

treebeard55

Another technique I've heard of is to place each pot into another container, one large enough for several inches clearance around the sides of the bonsai pot itself. Fill the gap between the two pots with sphagnum peat (or something similar) and keep the sphagnum moist. Evaporative cooling, again, is what does the trick.

I've not tried this technique myself, but have heard good things about it.

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Treebeard 55

"To do bunjin is easy. However, to do a bunjin masterpiece is difficult." -- Susumu Nakamura, at MBS '07