Heatwave gardening: German expert advises 10-20 litres per square metre, morning watering, and no more lawns

Heatwaves challenge not only people but also garden plants, which suffer from drought, sunburn, and water stress. Gerd Bergmann, an expert at the Hessische Gartenakademie, offers a set of practical measures to help gardens survive the summer.

Watering: how much and when

Bergmann stresses that superficial watering is ineffective. "When you water, don't just do a little bit, but water thoroughly and deeply so the roots in the lower area also get water," he says.

Thorough means 10 to 20 litres per square metre. The best time is morning between 6:00 and 9:00, when evaporation is lowest; if that is not possible, the evening after temperatures have dropped is the second-best option. Bergmann recommends using rainwater, but as it becomes scarce, he advises mixing it with tap water from the start.

Soil and evaporation

Bare soil loses moisture quickly. "You should not have open beds and areas," Bergmann warns. They should be covered with mulch or vegetation to keep moisture in the ground. Humus-rich soil, built up by adding compost, mulch, and organic biomass, stores water better. Lightly working the soil surface with a hoe also helps reduce evaporation.

Plant selection and lawn alternatives

Gardeners planning new plantings should choose varieties that can tolerate heat and drought. Bergmann also recommends mixed planting, whether for trees, shrubs, or perennials. "The risk of failure is then simply lower," he explains.

He is blunt about traditional lawns. "Generally I would recommend not planting any more lawns," he says. "You can see how brown they are everywhere." If a lawn is unavoidable, he suggests drought-tolerant species. Tall fescue (Rohrschwingel) is one of the most heat- and drought-tolerant grasses for home lawns; its deep roots need significantly less water than conventional turf. Microclover in the lawn also shows good drought tolerance, stays green longer than pure grass, and protects the soil from drying out with its dense leaves.

Tree care and shade

For trees, Bergmann advises a white coating against solar radiation. "That reflects the sunlight and prevents cracks," he says. The whitewash should be applied in autumn, in October or November, to provide protection for the entire following year. Sensitive or stressed plants need extra shade during heatwaves, which can be provided with umbrellas or shade sails. He also cautions against placing plants in front of white walls, as the reflected light causes them to dry out.

Pest management

Pests such as stink bugs and thrips are increasingly troubling gardeners. The most important defence is keeping plants well-nourished so they can resist attack. If an infestation occurs, Bergmann recommends natural remedies like soapy water. For stink bugs, however, only one method works: "collect them by hand."

For an infestation with stink bugs, only one thing helps: collect them by hand.

Gardeners with further questions can contact the free garden hotline of the Hessische Gartenakademie.