Some parts of Australia are enduring extremely hot weather and, apparently, there is more to come this summer. Periods of intense heat can cause scorching in many gardens.
Although European-based garden texts recommend full sun for most vegetables, where summers are hot and air pollution is low, full sun can result in sunscald. While Australian natives have evolved to restrict loss of water through leaves in hot, dry conditions, very hot plants, especially those that originated in cooler Northern Hemisphere regions – such as most of our vegetables and fruits, lose a lot of water through their leaves in an effort to keep cool, in a similar way to humans perspiring.
A bit of shade
Providing some light shade during the hottest part of the day can prevent sunscald on susceptible crops, and, by keeping the plants cooler, reduces their water consumption, an important consideration where water restrictions apply. We use lightweight, knitted shade cloth, supported by arches made from 38 mm irrigation pipe attached to garden stakes or star stakes, or you can use old light-weight curtains or sheets.
Each canopy is positioned to allow morning sun to reach plants, yet not restrict air flow around them. Poor air flow (such as in fully enclosed areas) can produce conditions suitable for some fungal diseases to establish. Instructions for making these can be found in the post Sun and heat protection.
However, in an emergency, any old curtains or pieces of lightweight fabric will do. Tie the corners to garden stakes to provide some relief for garden beds during the hottest part of the day.
If possible, move potted plants to a shaded area of the garden, and group them together. This provides more humidity around the plants, and reduces their water requirements.
Water is essential
Adequate soil moisture is essential for your vegetable garden to maintain good growth during heat waves. Mulching garden beds is very helpful. A method that we have found very helpful to water mulched beds is to use plastic soft drink and juice bottles to funnel water directly to the root area of susceptible plants. This is a quick and very efficient way to hand water during water restrictions, heat waves or windy weather. Limp tomato seedlings will freshen up in about 10 minutes after watering by this method.
Simply cut off the base of each container, remove the lids and bury the necks of the containers about 8 cm deep near outer edge of the foliage of plants. Large shrubs may require several containers. Pour water into the container until it begins to drain slowly – an indication that you have dampened the soil in the root area.
Seedlings and pot plants are usually the first to suffer during heat waves, and you can find advice on how to revive stressed pot plants here: Pot plant stress
Water for wildlife
Don’t forget to provide water for birds and bees that visit your garden. A bird bath, or containers of clean water positioned where cats and dogs can’t reach them will provide relief for the insect-eating birds and the bees that pollinate your crops. Chlorinated pool water is toxic to these helpful creatures. A container of water under shaded foliage will be appreciated by your resident frogs too.