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How to Help Your Garden Survive a Heatwave

How to Help Your Garden Survive a Heatwave

During most British summers we experience the occasional period of hot, dry, sunny weather. The media are quick to declare a heatwave, sending us all running for our hosepipes. But we should hold our horses ...... in reality, a mature garden planted with trees and shrubs won’t show any sign of distress unless a heatwave persists for a long period of time. Lawns may turn brown but little permanent damage is done if they are not watered. It's when we are caring for tropical houseplants, colourful summer bedding, planted containers or a cherished vegetable patch that we may need to take some simple precautions to ensure that our gardens remain healthy and happy until cooler weather returns. 

Whilst our natural instinct may be to water more regularly, the secret is actually to water more wisely, taking additional measures to reduce the amount of water plants need - that includes mulching or selecting naturally drought-tolerant plants. (You’ll find more tips on watering best practice in this ‘In The Know’ guide). As well as considering water, we need to remember that light levels on bright, sunny days can be exceptionally high, causing delicate foliage and pale skin to burn. For plants and gardeners the answer is the same - find some shade, cover up and keep cool if possible.

Here I share some of my top tips for helping your garden survive a heatwave or summer drought.

  • Houseplants - houseplants positioned on a sunny windowsill will dry out much more quickly during a heatwave - maybe twice as fast as normal or perhaps even more. If the compost in their pot is dry to the touch, give them a good drink, even if this breaks your normal watering routine. Unless you are going away on holiday, avoid leaving houseplants standing in a saucer of water for long periods as it will stagnate and turn sour: tip away any excess water once the roots have drawn up as much as they can. Move houseplants with large, dark-green or variegated leaves away from sunny windows as the leaves may scorch if they're exposed to too much sun. Even succulents will appreciate a little dappled shade - if they become too hot and dry they’ll stop growing and become dormant. The least vulnerable houseplants are those with silver-grey leaves. These have adapted to reflect sunlight and heat thereby keeping the plant cool.
  • Greenhouses - on hot days open all the windows and doors and sprinkle paths with water as often as you can - ventilation and ‘damping down’ will improve air circulation, lower the air temperature and increase humidity. Dry heat encourages red spider mites and powdery mildew, neither of which are easy to control once they take hold. Put up shading if you can, or move plants underneath greenhouse staging to give them some shade from the midday sun.
  • Pots and containers - pots, containers and hanging baskets will dry out very quickly during a heatwave and may need watering as often as twice daily. To reduce the burden, move any that you can into a cool, shady corner until the weather cools down again. If that's not possible, water them thoroughly, until water runs out of the drainage holes in the base of the container. If compost becomes very dry it may lose the ability to rehydrate - in this case stand the whole container in a bucket or trough of water and let it soak for a few hours or until it feels heavy again.

Drought tolerant planting

  • Flower garden - hot weather can shorten the life of many flowers, causing them to shrivel, fade and fall more quickly. Choose early morning or late evening to pick flowers for the house or give to friends - they will last for longer if harvested at cooler times of the day when they are nicely plumped up with water. Keep on top of deadheading so that flowers do not think it’s ‘game over’ and rush to produce seed prematurely. Plenty of plants will relish a heatwave provided they're well watered. You may be surprised how quickly they produce an sensational flush of flowers in response to sun and warmth. Plants from cooler parts of the world may cease flowering during a heatwave but don't worry as they'll pick up again later. As a rule, it’s not a good idea to feed plants when their roots are very dry. Water them first and then feed later.
  • Lawns - water lawns first thing in the morning if you can. It’s important to avoid having wet grass at night as this promotes the spread of diseases: the trick is to water so that the grass has time to dry before nightfall. Water thoroughly, until shallow puddles start to appear on the lawn surface and do this every 7-10 days. Resist the urge to give lawns a quick sprinkle as this encourages the development of shallow roots that are more vulnerable during droughts.
  • Trees and shrubs - even large plants may need watering during hot spells, particularly if they're newly planted. Give roses, fruit trees and flowering shrubs a good 5-10 litres of water every week if they're still getting established. Water at the base of the plant where it meets the ground. Mature trees and shrubs should be able to fend for themselves, although a heatwave lasting weeks or months could cause lasting damage that will manifest itself over time. Remember that plants growing beneath a tree will be quickly deprived of water as the tree will have a much bigger and thirstier root system.

Agapanthus and crinums

  • Vegetables and herbs - hot weather may cause leeks, spinach, lettuce, rocket and parsley to 'bolt' (flower and produce seed) sooner than you'd like. There is not a great deal you can do to prevent this, but planting in light or partial shade and regular watering should help. Harvest vegetables in the morning or evening and avoid picking during the heat of the day. Tomatoes are especially needy when it comes to regular watering and require special care during a heatwave. If they flip-flop between wet and dry the fruit may split and the whole crop could be ruined. Otherwise tomatoes should prosper during a heatwave, with the warmth improving flavour.
  • Wildlife - If water is scarce for plants it's probably scarce for birds, mammals and insects too. Provide a shallow source of water close to ground level so that bees, butterflies and hedgehogs can drink. Keep birdbaths regularly refreshed with clean water. If you have a pond, keep it topped up and make sure there are rocks or platforms for insects and animals to climb on to should they accidentally fall in while drinking. Remove blanket weed which can rapidly cover the water surface like a thick green fleece, suffocating aquatic plants and blocking out light.
  • Gardeners - be aware of just how fierce the sun can be in midsummer. Gardening can expose our skin to the sun in areas prone to burning. Ensure you apply sunscreen to your nose, ears, the back of your neck, the base of your back, the top of your feet and the top of your head. Wearing a hat definitely helps. Take a bottle of water with you everywhere you go and remember to drink it! Time your gardening activity so you can take advantage of the cool of the morning and balmy evenings. Critically, if you start to feel overheated or dizzy, take a break, go inside and drink plenty of water as soon as you can.

See Also

In The Know - How To Water Wisely

Enjoying Your Garden In June

watering chrysanthemums with a watering can

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