Bonsai Banter Issue 040 Bonsai and Heat

Bonsai and Heat

My daughter called me yesterday from Las Vegas (one of her favorite vacation spots.) “Mom, the temperature is 115 degrees!”

Angela is wise enough to stay indoors, but my thoughts turned to bonsai care when temperatures become this severe. Do the trees need to go indoors? No. However, it will help to drop the temperature of the containers, and in some cases put bonsai in the shade (especially pines).

I’m not in the habit of repeating issues of BonsaiBanter, but last year’s heat wave offered many ideas that I will share again in this issue.

The Heat is On!

These tips are from 2012, but are worthwhile reviewing when temperatures are severe.

… here in S. Indiana we have been experiencing severe heat and drought. Our trees are suffering. With this in mind, I just tried a new experiment and thought I would pass on my results. I have started covering my pots that sit in hot direct sun with heavy wet bath towels …

Experiment Details

Pots were covered with towel at 9:30 a.m. and watered heavily. Temperature checked at 2:00 p.m. in full sun, no shade or shade cloth.

Pot in direct sun soil temperature 112 degrees. Pot in full sun with wet towel covering pot – soil temperature 95 degrees.

After watering at 2:00 pm all soil temperatures of covered pots dropped below 90 degrees. (Soil temperatures were checked with a meat thermometer.)”

– Dave Bogan – Indianna, USA

Other Clever Techniques

You may want to try cutting 1/2 Styrofoam pieces that cover the pot on the sunny side, shim them up with a few rocks (or pieces of foam) and cut the trunk area out.

(Do not use the insulation styrofoam that has the foil on one side.) A larger rock on top holds them down.

The soil temps will be what the temps are in the shade … monitor them on windy days, but the blue Styrofoam does absorb and reflect the heat.

They can be easily removed for thorough watering.

– Kenny Popp, Louisville, KY, USA

Pauline Muth from upstate New York, added an especially easy resolution:

Here, we’ve been using boards slanted on the pot to the south… ”

A Note on Watering in the Heat

If you water with a garden hose, remember if the hose is in the sun, the first water to come out will be very HOT! And yes, it can damage your bonsai.

‘Normal’ Heat

If summer temperatures are normally in the 90s where you live, your bonsai will most likely be tolerant of the summers. You won’t need to do anything special. However . . .

Over the top temps can be dangerous to both humans and bonsai. Use caution!

Heat and Your Smallest Bonsai

Small amounts of soil (in small containers) add to the problem of high temperatures and your smallest bonsai trees.

Click here to get details about the illustration below and see the full page where I have more on shohin bonsai care.

More on Mulberry

In last month’s Bonsai Banter, I talked about mulberry bonsai. It wasn’t long before I received this photo. Thanks to Mitch Thomas for sharing his bonsai. I hope he will send another picture when it is fruiting!

Site Reminders

Until next month, thanks for your input and for visiting my site.


P.S. If you send me an email, photo or story and don’t hear from me, I may not have received it. Please try again!

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