Too Hot for Japanese Maples?

Maples are thirsty trees with shallow roots. Be sure you monitor them in the heat of summer.

This summer many places hit record high temperatures, as hot and dry as it has ever been. Many of your garden plants may have suffered, if they are still alive. To struggle so hard to achieve a perfect garden and lose some of your most beautiful plants is very difficult. Among the vulnerable and beloved plants are the Japanese Maples. . Extreme heat affects leaf color of Japanese Maples.


Japanese Maples (Acers)are usually the stars of any garden. So, if you are on a mission to keep yours healthy during record heat, the most important thing to remember is that maples are very thirsty trees with shallow roots. They dry out quickly if not watered frequently. Check that they are growing in well-drained soil. If not, amend the soil with sand or bark, especially if your yard is mostly hard clay. Mound up with good topsoil to ensure effective drainage. Water well at least three times a week.

Above all, monitor your tree. If there are dull brown leaves that are crisp and curling, it probably needs water. Since there are other causes for brown leaves, check the soil for moisture. Stick a long screwdriver or strong, thin, sharp stick into the soil below the tree. If that is hard to do, the tree needs more water. Or, to test for moisture, dig a 6-8” hole and take a handful of the soil from the bottom. It should be cool and moist. Roll it into a ball. If it crumbles, the tree needs more water. (If it is very wet, you are over-watering. If your soil is very sandy, it won’t form a ball, in that case, evaluate how damp the soil is.)

There are dozens of spectacular varieties of Japanese maple available, and they don’t all have same heat tolerances. Some are hardy in USDA Zones 5-7, for example, Acer shirasawanum, while others are better with heat, such as Zones 5-9 for varieties of Acer palmatum. If you are on the warm end the zones for your tree, for example Zone 7 for Acer shirasawanum, pay particular attention to it during record heat.

If the tree is struggling in the summer heat, you can add shading mesh for a few weeks to protect it from the sun. Consider moving it or planting taller trees around it for shade as more permanent solutions.

General advice for healthy Japanese maples:

  • When adding a new Japanese maple or moving one, plant it in partial shade. Do not plant it in a windy spot because there it will dry out more quickly.
  • Fertilize once at the beginning of each season with a good all-purpose slow-release fertilizer.
  • When summer heat is at its peak, check the soil and water frequently when dry.