Protecting fruit trees in a heatwave
How to protect fruit trees in a heatwave: deep watering beforehand, shade cloth, sunburn protection for fruit and trunks, and care once it cools.
Australian summers bring runs of days over 35 °C, and fruit trees feel them. Leaves scorch, fruit sunburns and drops, and young trees can die. A little preparation before the heat arrives makes most of the difference.
Before the heat: water deeply
A well-watered tree copes with heat far better than a dry one, because it can keep its leaves cool. One to two days before a heatwave, give every tree a long, deep soak that wets the soil well down into the root zone. Water in the early morning or evening.
- Check that drippers and hoses are working before you need them.
- Top up mulch to keep the soil cool and slow evaporation.
- Young and newly planted trees need water most, as their roots are small.
During the heat
- Keep watering deeply every day or two for young trees and heavy-cropping trees. Established trees on deep soil may need less.
- Water the soil, not the leaves. Wetting leaves in full sun does little to cool them.
- Don't fertilise, prune or transplant during a heatwave. Each one stresses the tree further.
Shade and sunburn
Fruit and bark on the hot western side of a tree burn first.
- Shade cloth of 30 to 50 per cent, put up over young or exposed trees for the worst days, cuts leaf and fruit temperature noticeably. Fix it on a frame so air can move underneath.
- Kaolin clay, a fine white clay sprayed on leaves and fruit, reflects sunlight and is used by many organic growers.
- White trunk paint: young trunks painted with water-based white paint diluted half and half with water are protected from sunscald.
- Keep leaf cover over the fruit. Avoid heavy summer pruning just before hot spells.
Which trees suffer most
Young trees, trees in pots, shallow-rooted citrus and avocados, and anything planted in the last year or two need the most care. Apples, pears and stone fruit carrying a heavy crop also struggle, as the fruit draws water from the tree.
After the heat
- Leave scorched leaves on the tree for now. They still shade the branches beneath them.
- Pick up and remove sunburnt or fallen fruit, which attracts pests.
- Wait until new growth appears before pruning out dead twigs, so you can see what really died.
- Give a light feed once the weather is cooler, if the tree is growing again.
Trees n Bees can send a hot day alert to your phone at the temperature you choose, giving you a day's warning to water deeply and get the shade cloth up. It also shows how many days of water are left in your tanks before a long hot spell.