When a heatwave hits, we move into the shade or ramp up the air-conditioning, but your garden plants are stuck where they are. And without taking pre-emptive measures, they will suffer terribly, even die.
Before a heatwave
Before a hot blast arrives, water your garden deeply in the morning. This goes for all plants, trees and lawns. If water hits foliage, the droplets will dry off as it warms up, reducing the risk of fungal disease. Don’t forget your potted plants – they dry out faster than plants in the soil, so they always need extra water.
Other ways to protect your plants include:
- Move potted plants indoors or under some shade.
- Add a seaweed solution to the watering regime – it’s a health tonic for roots and makes them stronger.
- Cover all bare soil with mulch, as this insulates the soil, keeping it cooler. Bare soil can get up to 10 degrees hotter than the air. In fire-prone areas, use an inorganic mulch such as pebbles or gravel.
Protecting indoor plants
If your house is lying in the hot sun, the water inside will also be hot and can scald plants. Run water into a bucket until it’s cold.
During a heatwave
The most important thing to do during a heatwave is to cover plants with shade. This will block excessive heat and burn from the sun. It can be a temporary solution, such as a garden or beach umbrella, white sheets or hessian, or a permanent fixture such as shade cloth.
Other ways to protect plants during a heatwave:
- Put cardboard or carpet onto or against these surfaces to reduce heat reflection from paving, walls, metal fences and rocks. Heat radiates from these garden structures, which can cause even shaded plants to burn, but you won’t notice the damage until after the heat has gone.
- Bring down any hanging baskets and move them and the pot plants into a shaded area. Group them so they create a humid atmosphere. Plastic pots, especially black ones, can really heat up and cook the roots.
After a heatwave
The harm a heat wave causes need not be permanent – quick treatment will have your garden looking as glorious as ever in no time!
After plants have been traumatised by a heat wave, you need to get as much water and air into the root zone as possible. The best way to do this is by making holes around the drip line of the plant with a garden fork to make water penetration easier. Make sure to water in the morning – afternoons will still be hot enough to make surface water evaporate before it gets to the roots. Water deeply and slowly so the soil is given time to absorb the water.
Plants have a built in heat response
Leaf drop, especially in trees, is an indication your plants are responding to heat stress. Leaves expire water, so leaf drop is a mechanism to prevent this. When the heat subsides, new foliage growth will kick into photosynthesis action.
Follow these steps to ensure your plants survive:
- If you haven’t done it before the heat wave, add water storage crystals to your soil. These tiny beads absorb water and release it over time, making watering more efficient. They are replenished every time you water.
- Keep wilted leaves on plants. They look ugly but act as a protective barrier for new foliage. Cutting them away encourages new growth, and immature growth is especially susceptible to extreme heat.
- When your lawns have turned into a brown fuzz, don’t despair. Those lifeless-looking blades of grass are still protecting the roots below, and roots absorb nutrients for the whole plant. Watering will encourage new blade growth, and your late summer/autumn lawns will look lush again.
- Watch out for soils that become hydrophobic, which can happen after prolonged hot weather. It means water doesn’t penetrate the soil, leaving roots thirsty. Apply a soil wetting agent to break down the waxy coating on top of the soil.
- Don’t fertilise your plants until the heat dies down. Plants need time to recover from a heat wave, and feeding them extra nutrients to trigger new growth adds new stress. Add liquid seaweed fertiliser to your soil to encourage root development and subsequently thicken the cell walls of leaves, making them more resistant to extreme weather.
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