Help Plants Beat the Summer Heat

It’s hot here. I thought I would never say that. And sure, it’s not as hot as Phoenix, but even mountain communities in the Southwest can warm up in summer months. When the temperatures hit the 90s, the humidity stays below 25 percent, and the winds never subside, vegetables and ornamental plants get stressed.

columbine northeastern exposure
In May, this columbine was blooming and healthy! It’s a little stressed now. Columbines grow naturally under the shade of trees, and they need deep water as temperatures rise into the 70s and higher. We mulched around the plant and put it in a northeast-facing location to help it survive summer.

Often, our first reaction is to throw more water on a plant. Sometimes, that’s what they need. Wind, sun and heat dry plants more quickly. Native xeric plants are adapted to take some of the parching sun and wind, and sometimes a gardener can overwater a plant. Here are a few tips to keep xeric plants cool, healthy and happy during the heat of summer:

  • Start with the right plant for the right spot. That means not only a native selection, but choosing sun vs. shade or the right drainage. Most xeric plants can take plenty of sun, but some need partial shade. And most don’t take kindly to wet feet, or roots that fail to dry between watering. Wet feet can happen with overwatering or if you place lavender in poorly draining soil at the bottom of a hill, or hide it under a bush that grows quickly and shades it within a year. You also can plan ahead to take advantage of shade. It’s getting too hot for my lettuce, but we’ll plant some more north of the fence holding the pole beans as soon as they get a little taller.
garden plan for shade
The sun is so bright, it’s reflecting off the spot where we hope to get some shade for lettuce and spinach. You can see the bean seedlings on the other side of the foreground fence shadow.
  • Follow the sun. When you plant in spring, the sun and shade patterns are different than they will be in mid-July and August. So keep in mind the sun’s direction and any plants or structures that might help shade a plant late in the day, when the sun’s rays are their hottest. Remember that deciduous trees might be nearly bare when you plant, but loaded by mid-June.
  • When helping a new plant get established, the typical care instructions might not apply. The plant goes into a sort of shock, much like when you recover from illness or injury. All plants need a little more water, as well as extra sun and wind protection until established. We’ve often used portable lawn chairs to provide filtered shade over new plantings in the afternoon. Old sheets or landscape fabric also work.
  • Use containers. If you have a plant that’s more susceptible to heat stress, place it in a container. You can move it around throughout the summer based on the sun’s path. Of course, if you really love the plant and have lots of time on your hands (and wheels under a larger container), you can move it around during the day, giving it morning sun and afternoon shade.

    tomato in container
    The tomato seedlings I planted in containers are doing better than many in the ground. The patio and house warmed them up during cool nights, but provide shade now on hot afternoons.
  • Water in the morning. It’s tough to find time before work, but watering early in the day loads your plant up, preparing it for the heat. And try to keep soil evenly moist. If you have a slow drip system, the irrigation can run while you get ready for work. Cover the drip hose with a nice, thick layer of mulch and the mulch will slow the water’s evaporation and help keep the ground cool. And as I’ve said before, it’s good to keep an eye on tomatoes and other vegetables and to have someone care for them if you leave town. Once the fruit sets, you can’t drown the tomato to make up for a few days of heat and underwatering. They’ll punish you.

Finally, drink some iced tea, flavored with a small bit of fresh mint. Oh, wait, that’s for me…

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