Beating the heat

Here’s how to protect your garden from the mid-summer heat.

There is no doubt that climate change has pushed up the daily temperatures and and gardens are visibly suffering.

All one can do when temperatures are consistently in the mid to upper 30⁰C is to be strategic about watering, protect young plants and keep the soil as cool as possible.

Gardening is always an act of faith and under these conditions one just needs to remember that when the temperatures drop, and the rain comes (hopefully) that garden will recover. However, rose grower Ludwig Taschner always reminds gardeners that 15mm of rain is only the equivalent of one good watering. Less than that means that one still needs to water.

Until then here are some strategies to keep the garden going during extreme heat.

Water on green leaves. Image supplied by Alice Coetzee

Wise watering tips

Water early in the morning or late afternoon. The nights are so hot that the leaves will dry off and not be affected by fungus disease. Watering during the heat of the day is a waste of water because so much of it evaporates. Also, plants are under such stress from the heat that they cannot uptake water efficiently.

Plants in containers should be watered every day but this can be done with harvested rainwater or greywater. Place the plants on a saucer filled with bark chips or coarse wet sand so that all the water that runs through is not lost. This supplies moisture without rotting Through a process of osmosis the plants will draw up the excess water.

Roses and azaleas will appreciate a brief spraying of their leaves with water at midday. This cools down them down and relieves a little of the leaf stress.

Avoid planting, transplanting and heavy pruning in hot weather. Loosen hard, compacted soil so that water can penetrate and add in plenty of compost to improve drainage.

longer lawn grass. Image supplied by Alice Coetzee

Set the lawn mower on its highest setting. Longer grass provides more shade for itself and the soil doesn’t dry out as quickly.

Don’t fertilise the lawn or any plants during extreme heat. New growth places higher water demands on the plants. If you feel that plants need nourishment rather use a liquid fertiliser.

Shaded veggie garden. Image supplied by Alice Coetzee

Provide temporary shade with 60% shade cloth for tender vegetables, seed beds and newly transplanted seedlings. The shade cloth should be raised high enough for the air to circulate.

Potted veggies can also be protected under shade cloth and the containers don’t dry out as quickly.

Sink two-litre plastic cold drink bottles into the soil next to particularly thirsty plants. The cap end should be buried (without the cap) at root level and the broader base cut off so that water can be poured in. Fill the bottle daily. This gets water directly to the roots and lasts longer without evaporating. This also encourages the roots to go deep into the cooler soil, rather than staying on the surface where they quickly dry out.


Simple rule for watering

There is no argument that in a heat wave, plants must be watered but it is important not to overwater plants, so if the heatwave lasts more than three days, skip a day between providing extra water.

A small amount of water to ‘refresh’ doesn’t help. The roots of plants need to go deep where they can access water and that only happens  with deep watering less often. The closer the roots are to the surface the less drought tolerant they are.


Mulching saves water

leaf mulch. Image supplied by Alice Coetzee

Because water is so precious, especially with water restrictions, the aim is to make sure as little as possible is lost through evaporation.

Bare soil bakes dry in an instant and the only way to prevent it is by mulching. Spread a shallow layer of mulch (about 2cm) of organic material on the soil surface, around plants and on the surface of containers. Do not make the mulch too thick because it can prevent water, and vital rainwater, from penetrating.

However, a light mulch (which is renewed regularly) keeps the soil cool and moister for longer, protecting the roots of the plants and also the soil life.

Mulch can be a mix of leaves and dried lawn cuttings, pine needles, peanut shells, bark chips, or hay. Lighter coloured mulch reflects that heat away from the plants and helps keep the soil surface cooler.


Good to know:

Plants with big leaves, like squash, wilt easily as a way of conserving water. They generally perk up when the sun moves over. But, if the leaves stay wilted, water immediately otherwise the plants will die.

For shrubs, veggies and even perennials, make a bowl around the plant by damming up the edges. This prevents run-off and the water seeps through to the root ball, which draws the roots downwards.

If possible, move pots to a shadier spot during the hottest periods. Water in the mornings and on extreme days you may need to water in the afternoon as well. Add a soil-wetting agent to the potting mix  to help pot plants last longer between waterings.


Plants you can count on

Statice and Kalanchoe. Image supplied by Alice Coetzee

South African indigenous plants like agapanthus, wild iris, plumbago, sages, wild garlic, and aloes are all extremely drought tolerant. So too are garden flowers originally from other arid regions like statice, salvia, and bromeliads, that have proven staying power in this country.


Article supplied by Alice Coetzee. 

For more on gardening, visit Get It Magazine.

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