Avoid This Common Mistake When Watering Plants in a Heatwave
As the UK swelters through a heatwave with temperatures expected to hit 34°C this weekend, many gardeners are unknowingly making a crucial mistake that could be killing their plants.
The mistake is simple – watering your plants from above. Josh Novell, gardening expert at Polhill Garden Centre, says that while it might seem intuitive to pour water over your plants during hot weather, top watering can actually do more harm than good.
“In intense heat, watering from above can scorch the leaves, waste water through evaporation, and even increase the risk of fungal diseases like powdery mildew and black spot,” Josh explains. “Bottom-watering is a far more effective method, especially during a heatwave.”
Why you should be bottom-watering
Bottom-watering involves applying water directly to the base of the plant, allowing moisture to soak through the soil and reach the roots efficiently. Not only does this method prevent leaf damage, it also encourages stronger root growth, which helps plants become more resilient in extreme conditions.
“Bottom-watering encourages plants to develop deep, strong root systems,” says Josh. “This makes them better able to withstand heat and drought in the long run.”
Another benefit is that it reduces the likelihood of diseases caused by excess moisture sitting on leaves and stems, like rust, powdery mildew, and black spot, which can weaken or even kill plants during hot, humid spells.
The dangers of overwatering
Many well-meaning gardeners respond to heatwaves by giving their plants extra water, but this can actually backfire.
“Overwatering can saturate the soil, block air flow, and prevent nutrients from reaching the roots,” Josh warns. “If your soil doesn’t drain well, like clay or silty soils, you risk root rot and suffocation.”
For best results, Josh recommends using sandy or loamy soil and containers with good drainage. A long-handled watering wand can also help you reach the base of plants, hanging baskets, and tight spots without wetting the foliage.
How to bottom-water correctly
- Use a watering can or hose to apply water directly at the base of the plant.
- Avoid splashing the leaves or stems.
- Water deeply every 2-3 days instead of giving quick daily sprinkles.
- Use trays under pots to allow plants to absorb moisture from the bottom up.
“Always water early in the morning or in the evening,” Josh advises. “This gives the water time to soak in before it evaporates in the midday sun.”
“And be patient, let the water soak in slowly to avoid runoff or pooling,” he adds.
Exceptions to the rule
“Water lilies, rain lilies and other aquatic plants should be watered from above,” says Josh. “They need surface moisture to stay healthy because that’s how they’re designed to grow in nature.”
Herbs like mint, basil, and oregano are also happier with overhead watering, as are some vegetables.
“Tomatoes and peppers in pots often do well with gentle top watering,” Josh notes. “Just avoid splashing the leaves too much, as that can still lead to problems in extreme heat.”
Josh’s extra tips for heatwave plant care:
- “Adding a thick layer of mulch around your plants helps trap moisture in the soil and shields roots from the heat.”
- “Move potted plants into shade if you can, especially during the hottest part of the day. They’ll dry out faster than plants in the ground, so monitor them closely.”
- “Skip the fertiliser while it’s this hot as feeding plants in high heat can stress them even more. Wait until the temperature drops back down before feeding again.”
- “And don’t forget to check hanging baskets and containers. They need more frequent watering, but always aim for the soil, not the leaves.”