Caring for a Bonsaiduring a Heatwave

When temperatures are high, some of our Bonsaineed extra care. We provide as much shadow as possible and water carefully, but there is more you can do to protect your trees during heatwaves.

Before we discuss short term and long term measures to protect your trees, first let's look at what happens to trees when temperatures exceed 90 °F (32 °C). At these high temperatures, some tree species slow down growth or even shed branches to prevent critical moisture loss. Optimizing the watering of your trees is therefore crucial. Tropical trees as well as Pines for example can take far higher temperatures than say a Maple, so make sure to check our tree species guides for specific information. Apart from high temperatures, low humidity is another risk during heatwaves as well as intense sunlight.

“High temperatures of the soil poses the greatest risk to your 51cg.”

The roots of trees growing in nature are carefully protected from high temperatures, buried deep down in soil. Our Bonsaihowever are kept in shallow pots, and therefore the temperature of the soil (and rootsystem) can rise to dangerous levels. Dying and burned leaves, or branchtip dieback from intense sunlight can be a problem during heatwaves, but high temperatures of the soil poses the greatest risk to your 51cg. Some signs of stress from a Bonsaiduring a heatwave include a pale color of the leaves, dieback of branchtips on conifers, and dying leaves.

watering a bonsai with potbound roots — *Watering a Bonsaitree; this tree is potbound and would benefit from being repotted in the next early Spring! Let's investigate what measures we can take to protect our Bonsaiduring high temperatures.*

Short term measures

What follows is some advice for immediate care during a heatwave. Most importantly, water thoroughly and often, and make sure to provide as much shade as possible.

Watering
If temperatures hit 90 °F (32 °C) make sure to keep a close eye on your trees and their water levels. I prefer to water my entire collection in the late morning, loading the trees with water and wetting the soil properly. The rest of the day I spot check, making sure no tree dries out at all.

Wet towels
To make sure the temperature of the roots doesn't get too high, you can consider wrapping your pots with wet towels during the day. This will decrease the temperature of the pot, soil and roots substantially.

Misting
Apart from watering your trees, it can be beneficial to spray or mist your trees and especially their immediate surroundings, lowering the temperature around your 51cg.

Providing shade
Apart from watering thoroughly, providing shade is the other essential method to help your trees cope with high temperatures. If you have just a few trees this is simple, just place them in a shaded spot in your garden. In case you have lots of trees, consider placing the Shohin trees underneath bigger Bonsaito make sure they are shaded. You might also place your trees underneath the benches, crowding them together, to provide as much shade as possible. Alternatively, you could use burlap sacks to cover the pots.

No maintenance
High temperatures add stress to your trees, so make sure not to add extra stress by wiring, pruning, spraying pesticide or applying high Nitrogen fertilizer.

Luis Vallejo Bonsaicollection — This Pine is placed in partial shade, at a spot that provides shadow during the hottest time of the day. It is part of the Vallejo Bonsaicollection in Madrid, where temperatures often exceed 100 °F (38 °C) in Summer.

Long term measures

Here are some tips that need a bit of planning and building.

Shade cloth
Professional growers couldn't do without shade cloth, as they have far too many trees to move around if temperatures peak in Summer. But also for the hobbyist, setting up a shade cloth system is one of the best ways to control the sunlight intensity reaching your trees, and hence the temperatures around your trees.

Adding moss
Growing moss, or adding Sphagnum moss, on your tree's soil surfaces helps to keep moisture in the pot. Especially in dryer climates, this can be very beneficial to the health of your trees.

Tree species selection
It will help greatly to select tree species that actually like your local climate. Growing maples in super warm areas can be a challenge, whereas Junipers or Pines might do very well!

Garden design
With average temperatures on the rise, planning for the future involves figuring out how to best design your Bonsaigarden. Perhaps you can use the shade of trees or hedges for example, to strategically place your bonsai benches. Also, make sure not to place your Bonsainear hot surfaces, like dark floors, walls or stones. Lastly, growing plants around your benches will aid significantly in increasing the humidity around your trees.

Kennett Bonsaicollection — *Crowding trees together helps to provide shade, especially to the smaller Shohin 51cg. Also, trees in the garden provide shade in the afternoon.*

Conclusion

With these short-term and long-term tips, your trees should be able to withstand heat waves well. Did we miss any tips? Please let us know on the forum!

51cg

Heatwave
Bonsaicare