This week’s unprecedented heat has taken a toll on our gardens, leaving plants wilted, lawns browning and trees dropping their leaves months earlier than usual. There is almost certainly worse to come, as global heating makes 40C summers routine. So how can we bounce back from this challenge, and prepare for those ahead?
The first job is to survey the damage, and triage plants to identify those needing immediate help. Begin by launching rescue missions for anything in containers, window boxes and growbags: look for signs of drought stress such as wilted and curled leaves, as well as falling flower buds and dropped foliage. Stick smaller pots into a bucket of water, let them soak for an hour or two then remove and drain thoroughly – the aim is to completely rewet the rootball, and then make sure air can still reach the roots. Keep them in a shady spot to give them a chance to recover: even plants that look terminally crispy can often revive and re-sprout with this treatment. Larger pots should be heavily watered, then allowed to drain – one deep watering is better than daily sprinkles.
The other focus for your watering should be any trees or shrubs planted in the last couple of years. Their immature root systems leave them vulnerable during dry spells, so even if they look unchanged now, they may fail completely in the next few months. It’s fine to use “grey” water from your bathtub or washing up bowl to give these ornamentals a drink.
Don’t try to revive lawns by soaking them with a hose or using a sprinkler – if this is not the last heatwave of the year, any new growth will soon be wiped out by the next drought. Lawn grass is durable and will bounce back once rains do come, so watering is a waste. Also hold off mowing and fertilising lawns – leaving grass longer can help it cope with drought. If you must mow, take care not to pile grass clippings in a large heap, as this can pose a fire risk in hot weather.
It’s tempting to prune off sun-damaged growth from trees and shrubs straight away, but, as with the lawn, it is wise to avoid stimulating new growth that could get wiped out in another temperature spike. The damaged growth will also continue to serve as shade for the rest of the foliage, and can be trimmed off later in the year.
Houseplants that were left outside or not shielded from direct sun during the heatwave may be showing strawlike marks – the result of tissue damage from UV light. Move them to a spot out of the sun to avoid a repeat performance: the marks will not disappear, but new growth should emerge to replace the damaged areas in time. Remember that wilting can be a symptom of waterlogging as well as dryness, so always check houseplants’ rootballs for moisture before watering.
Consider which areas of your plot have suffered most and how you can protect them in future. Despite the current trend for gardens that look like outdoor rooms devoid of plants, adding more greenery to your space will help it stand up better to extreme heat and provide shelter for you and your pets as well as garden wildlife. For instance, a greenhouse, conservatory or cold frame surrounded by plants will stay cooler than one standing exposed; if that’s not possible, consider covering it with removable shade netting, blinds, or even old cotton sheets, to keep the sun at bay during heatwaves. Adding a pond, even a small one, can help create a cooler microclimate, as well as providing water and habitats for wildlife. Cut down on the number of water-hogging containers you plant up for summer: try switching lots of small pots for one larger one planted with several plants that will not dry out as quickly. Removing areas of lawn and, instead, planting shrubs and trees will add valuable shade, but if you must have grass, make sure it’s the real thing. Artificial grass gets dangerously hot during summer and is an ecological disaster.
Canny plant choices will also help save your garden from future damage. Drought-resistant species often have leaves that are silvery to reflect sunlight, succulent to store water, or leathery to slow down water loss. For instance, sea hollies (Eryngium species) and lavenders do well in full sun, while hellebores and the false castor oil plant (Fatsia japonica) thrive in dry shade. For summer bedding, try pelargoniums, sunflowers, cosmos and dahlias.
If another heatwave is forecast, placing old net curtains or horticultural fleece over vulnerable indoor and outdoor plants that cannot be moved will help protect them from the sun. Do everything you can to add organic matter to your soil, as this will help it hold on to moisture during dry spells: if you don’t have a compost heap, start one, as it’s a great way to generate a free source of soil improver. Mulching soils and the tops of pots with a thick layer of bark chips or homemade compost in spring when the soil is still moist also helps to stop water loss as it warms up. Invest in as many rainwater butts as you have downpipes to save precious water supplies and help cut your water bill. And, finally, leave out shallow dishes of water containing a few pebbles, so that wildlife – from bees to hedgehogs – can have a drink.
