It’s HOT! Help your trees and plants cope.

With days over 100 degrees, trees and plants are struggling to cope. You've spent a lot of time and money installing and maintaining your landscape. You don't want your trees and other plants to be damaged by heat spells. What can you do to help?

Trees and plants can be damaged by excessive heat and not enough water. Dead, leafless branches are a good indication that this tree is in trouble and is struggling to survive. The paving reflects heat making the already hot days even hotter.

Plants need water to keep their foliage cool. They use more water when the temperatures are hot. With watering restrictions in place, your landscape is likely to experience stress in extra hot weather.

Drought stressed tree with dead branches

Are your trees and plants in trouble? Here is what to look for.

Pale shrub in front is drought stressed, darker shrub in back has enoggh water

Paler than normal leaves can be the first sign of water stress. The shrub in the front has pale leaves and needs more water. The shrub in the background has normal dark green leaves and has adequate water.

Plants have different colored leaves, and what is pale for one species may be normal for another. So it helps to be familiar with your plants' normal color.

Provide some water and the pale shrub will recover, probably with no permanent damage.

These symptoms indicate more serious water/heat stress.

leaves with brown, dead edges
Dead edges on leaves
Dead brown spots on leaves
Dead brown spots on leaves
wilted leaves and non-wilted leaves
Leaves on the left side are wilted and curled toward the underside due to drought stress. The leaves on the right side have enough water.

If you see these symptoms, your trees and plants need help right away.

First, check if the soil is moist. You can dig a small hole 12" deep and feel the soil with your fingers.

  • If it is dry it will be hard to dig or feel crumbly and dry.
  • Moist soil should feel like a piece of cake. You can feel the moisture, but it isn't muddy. This is what you want.
  • Wet soil is semi-liquid, more like pudding.

Digging a hole and feeling the soil with your fingers is the best way to check your soil's moisture. But if you cannot dig a hole, you can try a moisture meter. They are not very accurate in sandy or rocky soil, and may show "dry" even immediately after you water. They are more accurate in soils with a lot of clay. Clay holds a lot more water than other soil types so it registers better on the meter.

If your soil is wet, like pudding, do not add more water to the soil. Plants need both air water in the soil to stay healthy, and if your soil already has too much water there is no room left for the air. Letting the soil dry out a little allows the air back into the soil.

To make diagnosis more complicated, sometimes when plants are growing in poorly drained or over-watered soil the leaves can look just like a plant that needs more water. That is why it is best to check the soil, rather than just look at the leaves.

Let the soil dry for a couple days then check it again. Remember, you want soil that is moist like cake, not wet like pudding.

For dry soil, add water. You can use sprinklers, "oozy" hose, or drip lines. You may be able to run your irrigation system for an extra time a week for these very hot weeks.

If your tree is looking poorly and it is normally watered by a drip system, does the drip system provide water to the entire area under the canopy? We frequently see mature trees that are subsisting on the original two drip emitters that were installed when the tree was planted.

See the drawing below for where you should be watering your tree.

Where to water a tree
Graphic of tree and where to apply water
Apply water under the canopy of the tree and a little way beyond. For established trees you don't need to water right next to the trunk.