Hot-weather tips for roses

The low levels of dams supplying our urban areas means that water must be used far more sparingly. Gardeners need to get the balance right between using water responsibly and keeping their roses alive, should this hot, dry period continue.

Rose bushes with leaves from top to bottom cope best with the heat because the leaves shade the stems and cool the plant. They survive by going semidormant, with slightly curled hanging leaves. By shutting down, evaporation through the leaves is limited and less food and water is required survive. It is normal to see a few more yellow leaves on the inside and lower down on the bushes during hot weather. Again, it is an internal water saving mode.

We can help roses to cope by the way we care for them. Cut off as little as possible during a heat period. Cutting stems encourages sprouting of dormant eyes and this requires extra water. Rather leave dead blooms on the bush or just cut off the head. The aim is to keep as many leaves as possible to shade the stems of the bush. Defoliated bushes have no protection and may get sunburnt, leading to stem kanker. Cover such bushes with a very light frost guard cloth or double shade cloth for two weeks. By that time many eyes should have sprouted, restoring the sap flow.

Do not fertilise because this also stimulates new growth. Fertilising without watering afterwards will burn the stems and leaves and could kill them. Make every drop of water count. So often, water intended for roses gets sucked up by the roots of nearby plants. One way to make sure it gets to the roots is to sink a two-litre cool drink bottle into the soil so the neck (without the cap) is at root level. Cut off the base of the bottle, so the bottle can be filled with water. Filling that bottle every day will provide the rose with the 10-litres of water a week they need.

Roses can survive with grey water, from the shower, washing machine or kitchen, using ecofriendly cleaning agents. Keep a bowl in your kitchen basin and save the water from washing vegetables or your hands. Where root competition is not a problem, just one deep watering a week will see the roses through. Mulch the beds with a one to two-centimetre layer of organic material. This keeps the soil cool, even if it dries out. However, don’t make the layer too thick; water needs to penetrate easily so leave a gap around the stems. Put container roses on to saucers so the water that drains through is not lost.

On very hot days, the capillary action will draw up excess water. Containers, especially plastic ones, can get very hot, especially if they receive direct afternoon sun. Move them into a position that receives afternoon shade, wrap them with hessian (or other material), or drop the pot into a slightly bigger one that will act as a sun buffer. When you water makes a difference. The best is early morning or after 6pm. The nights are hot enough for the leaves to dry off quickly.

On very hot days, cool down the roses with a quick five-minute shower from the sprinkler or hand-held hose. When you feel like a shower, so do the roses. It will help to slow down the transpiration rate. Red spider often occurs when the downward sap flow slows, which is caused by rapid evaporation from the leaves, with no water returning to the roots.

Spraying once a week with Ludwig’s Insect Spray and drenching the underside of the leaves, will prevent infestations. The best thing to do is keep an eye on your roses. If they look a little droopy give them with some more water. If they aren’t droopy leave them alone.

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