I love summertime in my garden. The long days lure me from my office to spend hours outside…
I know that the intense sun and dry air can dehydrate me and burn my skin to a crisp if I’m not careful. But what happens to our plants and gardens when temperatures soar and the humidity takes a nosedive?
Here are common indicators of summer garden stress and why they happen.
Signs of Water Stress
Consider how water moves through plants: we water soil so the water can enter plants through their roots. From the roots, water travels up through stems and branches, ultimately into the leaves.

Plants cleverly curl their leaves in extreme heat to protect themselves from sunburn and dehydration.
That water doesn’t stay in the plant, however. It moves through the leaves into the air by evaporation and by a process called “transpiration,” which is similar to the way water vapor goes into the air when you exhale.
This process of water entering and leaving plants happens constantly. Under most conditions, the two are in balance. But in the extreme heat, sunlight, and aridity, the process gets out of whack; plants lose water faster than they can replace it. This imbalance causes the plant to be water stressed.
How do you recognize water stress?
- Curled leaves, aka “taco” leaves, curl inward along the edges to the point where they almost fold in half. Curled leaves are common in water-stressed citrus, shrubs, and other trees. Leaves curl or fold to reduce the surface area that’s exposed to air, limiting ways that water can escape. At the same time, the curl protects the leaf from intense sunlight. Clever, right? If just one leaf curls, there’s probably a cocoon inside, but if all the leaves curl, it’s water stress.
- Droopy leaves and branches. When soft-stemmed plants lose water faster than the water is replaced, their leaves droop rather than curl. As the imbalance increases, branches droop, too.

These unsightly spots on your tomatoes are caused by blossom end rot.
- Soft, mushy brown spots on the bottom ends of squash and tomatoes are classic symptoms of blossom end rot, which is also a problem with water management—not a lack of calcium, as many sources claim.
- Sudden plant death, especially with California native plants and plants from Australia and South Africa. This is a case of too much water. We often think we need to water more through summer’s heat. But these plants evolve in regions where there’s no summer rainfall; they are perfectly adapted to staying dry all summer. Beyond that, in our region, irrigating warm soils supports a fungus that attacks the roots of these plants. If you tend to lose these kinds of plants suddenly—they seem to turn brown overnight or over just a few days—between late July and late October, it’s likely they were overwatered.
Signs of Sun Stress
Just like us, plants can be damaged by intense sunlight. Some sun issues are indistinguishable from water issues—others are clearly different.
- Dead blotches on tomato and pepper fruits, whether brown or yellowish, are quite literally sunburn. The fruits are still edible but the burn is permanent.
- Dead, flaking bark on trees, most common on citrus and avocado but sometimes on other trees. Sunburn also damages or kills the bark on these trees. One benefit of growing dense branches of leaves is that they shade the bark.
- Newly planted plants droop. Recently planted plants need time to grow new roots, which allow them to grow the branches and leaves that shade them. In the meantime, they’ll droop in response to the intense sunlight.
Signs of stress in your plants can be concerning. The good news is that these stressors can be prevented. That will be the focus of my upcoming webinar, “Summer Garden Care.” We’ll chat through how to protect your garden in our intense, Southern California summer. I’ll cover topics like:
- What are ways to create temporary shade to protect plants from intense sunlight?
- How do you deal with summer pests like spider mites, tomato hornworms, and others?
- What about managing irrigation, protecting soils, supporting bees, birds, and butterflies in the heat?
Join me this Thursday, July 18th, at 7 PM PST to learn how to keep your garden thriving all summer long. Tickets are on sale now.