July 29, 2026, 3:27 pm | Read time: 3 minutes
A heat wave means stress for plants. Many hobby gardeners try to support their flowers, perennials, and vegetable plants with extra care. However, not every measure is sensible. Whether it’s frequent watering, fertilizing, or pruning–some interventions can further weaken the plants, especially in high temperatures. myHOMEBOOK gardening expert Franka Kruse-Gering explains which mistakes to avoid with plants during heat.
1. Mistake: Watering in the midday heat
When the sun is blazing, many hobby gardeners feel guilty and spontaneously reach for the watering can. But that’s the worst time to do it. The ground is highly heated, so some of the water evaporates before it can even reach the roots. This often only helps the plants temporarily. It’s more effective to water early in the morning when the soil is still cool and the water evaporates more slowly. This way, plants can better fill their water reserves for the hot day.
Also interesting: Watering lawns correctly during heat–expert warns against “constant drinkers”
2. Mistake: Watering plants a little every day
Many garden owners mean well and give their plants a small amount of water daily. The problem: The moisture often only reaches the top few inches of soil. As a result, plants develop shallow roots that dry out quickly during the next heat wave. This also applies to lawns, confirms Dr. Harald Nonn, former chairman of the German Lawn Society, in a conversation with myHOMEBOOK: “If I water a little every day, I draw the lawn’s roots upward. Then I have to water more often than with deeper roots.” It’s much better to water less frequently but thoroughly. This way, the soil is moistened in deeper layers, and the roots grow where the soil stays moist longer.
3. Mistake: Fertilizing during extreme heat
When plants look limp, it’s easy to assume they lack nutrients. In many cases, however, they simply suffer from drought stress. An additional round of fertilizer can even be counterproductive. The fertilizer stimulates the growth of new shoots, even though the plant should actually be using its energy to survive the heat period. During a heat wave, restraint is advised.
4. Mistake: Pruning wilted plants immediately
Drooping or curled leaves look dramatic but are often just a protective reaction against strong sunlight and water shortage. Those who hastily reach for the shears and remove large parts of the plant add additional stress to the plants. Many plants recover once temperatures drop or they receive enough water. Therefore, it’s worth waiting to prune until after the heat period.
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5. Mistake: Mowing the lawn as short as possible
A short-cut lawn looks neat at first glance, but it’s a disadvantage in summer heat. The blades shade the ground less, causing it to dry out faster, explains Dr. Harald Nonn. Additionally, the grass itself can burn more easily. During a heat wave, the lawn should be left a bit longer.
6. Mistake: Planting new plants now
Even if the garden center is tempting, heat periods are not a good time for new plantings. Newly planted perennials, shrubs, or vegetable plants do not yet have a sufficiently developed root system and must simultaneously establish themselves and cope with the dryness. This increases the risk that they will not establish well or even die. It’s better to plant new plants on cooler days or wait for the next weather change.