Something to think about when combating summer's heat...

Wm Tom Davis

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Ojai, California
I came across an internet article by Andy Walsh regarding something many people forget about, especially now as temps rise and we over water in hopes of "cooling" the trees down a bit.

Many of my trees are in black plastic pots. I use them to try and get more growth while my trees are relatively young (less that 10 yrs). I live in a semi arid part of California, where lately the temps are in the upper 90's. Some of my trees were getting dry tips in their leaves and needles, so I have been watering and misting the the early morning. I do keep and eye on how damp the soil is, but one thing that I've been noticing is that the soil is a bit warm (black plastic pots).

So I did a search online and found this very informative article about root heat and that it can kill trees fairly quickly.

Here is the link:

I hope this helps someone in someway...
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We have recently had a number of days in the high 90's with some up to 108. In the summer I protect some trees with slabs of slate behind the pots that get afternoon sun. This blocks the direct sun on the pot and keeps the soil cooler. It looks quite acceptable.

I also tend to "over pot" some of my trees to get them out of the hot plastic nursery pots and into a ceramic home. Therefore, I have a number of trees in training that are potted up in bonsai pots. The pots are by no means the appropriate size. They do add an air of respectability to the young'ins.

For those still in plastic, I moved most of them into more shade.
Try 115 out here. I grow hornbeams and maples in this heat. Shade cloth goes up after it starts hitting about 90 wet towels over the pots and or rocks on the soil. I believe the most important thing is to get your roots right as that is what will keep the water up to the leaves and to also modify the micro climate as much as possible. Water trays are not enough. What really works is lush broad leaf plants under and near your trees. This will humidify the air much more than even a pond. On a hot day walk into a lush garden area and you can feel the difference in temperature. I think Hostas are perfect.
I had always thought it was bull but I will also be trying the drought shield that you can spray on the leaves this year. It is meant to reduce transpiration by 50%. I can't remember what article changed my mind but I will see what happens this year.
Right! Here it's been averaging about 95 since March. I intalled 20% shade over the trees, most are in bigger pots and in this part of 'Nam--and right on the coast it's pretty windy. I however, water twice a day, mist a few other times and hose down the area around the plants.

I have moved my trees to a shady area and they seem to be responding well. The humidity is about 25% so its not that bad. I don't have the space to put up shade cloth, but in the future when I get back to California I will definitely find a spot that will afford me space to do so.

Yamadori, I like the idea of doing something to block the sun light on the pot.

Bretts, I went and bought some light colored roof rock, sifted it to size and have covered the top of my soil with it. I agree that this will help keep the soil from drying out so quickly from the heat.

head_cutter, I have been keeping a regimen of misting every morning, and now that its getting hotter and the soil is transpiring more from the heat, I have stepped up my watering schedule from twice a week to every two days. Seems to be working...

Many thanks for the replies!
I'm very appreciative of your responses.
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