The 20 plants that need extra water during a heatwave, if you want them to flourish all summer

There’s nothing more depressing than when your once thriving vegetable garden starts to lack vigour under the intensity of the heat, and stops producing. Crops producing large fruits or leafy growth require substantial amounts of moisture to maintain healthy development.

1. Tomatoes

Tomatoes are ever so thirsty, and irregular watering during hot weather can cause fruits to split, while fluctuating soil moisture often leads to blossom end rot, which is a dark, sunken patch that develops on the base of fruits. You should water your tomatoes deeply and consistently, at least once every one to two days, which is far better than just a light sprinkle of water little and often. Direct the water to the base of the plant so that you avoid wetting the foliage. 

2. Cucumbers

One of my favourites to grow because I dice them up into Greek salads, which is a delicious hot-weather lunch. They are made up of more than 90% water, and so can very easily become stressed in dry conditions. Plants that are not watered will produce bitter-tasting fruits, and prolonged drought can dramatically reduce your desired cropping. Try to keep the soil consistently moist and mulch around the base to conserve that valuable moisture.

3. Courgettes, Pumpkins and Squash

Some of the largest stars of the garden, is anything more delightful than a courgette glut in the summer months? These vigorous plants produce ginormous leaves that lose large amounts of water through transpiration, and during a heatwave, they are prone to wilting dramatically in the afternoon sunshine, even if the soil moisture is adequate. Long periods of drought will reduce fruit production and stunt growth. Deep watering every few days is far more effective than frequent light watering, so don’t be shy and give your courgettes, pumpkins and squash a hearty drink. 

4. Melons 

It’s my first year growing melons in my garden, and I’m eagerly awaiting harvest time. They’re a tad annoying to grow as they require a near constant supply of water, so I’m sure to give them a long drink every day. If you don’t, you risk a plant that produces smaller fruits that aren’t bursting with that treasured sweetness and flavour, or just a smaller yield, full stop. 

5. Celery 

I’ll confess, it’s not my favourite vegetable of them all, but it’s still a valuable addition to salads and green juices (on the rare occasion I have those!) Arguably, celery is one of the least drought-tolerant vegetables that you might choose to grow in your garden. It really thrives in moist conditions and develops tough, stringy stems if it lacks hydration, which will certainly not be pleasant to eat. 

Other vegetables to consider additional watering during a heatwave 

Peppers, aubergines, sweetcorn, French beans, runner beans, cabbage, and broccoli are also worth monitoring in hot weather. They don’t require as much maintenance as the list above, but they will still benefit from a consistently moist soil whilst they are producing crop. 

Fruit crops that need extra water during a heatwave 

1. Strawberries

One of my favourites, the sparkling red jewels in the garden, that I have been growing in abundance until my small dog found its way into the greenhouse and feasted on! A thirsty plant will produce far smaller berries, which would be a shame after all the effort put into growing them, if you allow them to dry out. It also helps keep the fruits’ distinctive sweet flavour, too.

2. Blueberries

Bursting with antioxidants, a handful of blueberries is one of the best summer snacks you can indulge in, and they are a pleasure to grow, but because they have shallow root systems, they do dry out much faster than many fruit bushes. To combat this, water your blueberry plant regularly during hot spells, particularly if you grow them in containers where the water will evaporate more quickly. 

3. Raspberries

Deliciously sweet and dreamy in crumbles or atop natural yoghurt, raspberries are a summer star. Developing canes require a steady water supply while fruits ripen, so water regularly three times a week during the most intense weather. Drought will lead to poor berry size and a loss of that much-beloved sweetness, as well as shortening the harvest period, so be ample in your watering efforts. 

Other fruit crops to consider additional watering during a heatwave

Although the list above is your top priority, it’s worth also considering younger plants, as they have limited root systems and will struggle to withstand the more prolonged dry weather than more established plants. Citrus trees grown in pots and grapevines grown in containers are worth paying attention to as well, by keeping their soil consistently moist. 

Herbs that need extra water during a heatwave 

Mediterranean species of herbs like rosemary, thyme, oregano, and sage are naturally drought-tolerant and have adapted to hot and dry conditions, so these are fantastic to grow across the year. However, there are a few soft, leafy herbs that need adequate watering during long periods of hot sunshine.

1. Basil 

It’s one of the most versatile herbs you can grow as it’s as delicious dressing a plate of mozzarella as it is sprinkled on a lamb laab dish, but it’s simultaneously one of the thirstiest herbs you can grow, with its large and tender leaves easily losing moisture and wilting if not given a drink regularly. Keep your basil plant evenly moist, especially when you are growing in containers, to encourage fresh and leafy growth.

2. Coriander

Coriander is aromatic and brings distinctive magic to sauces, but it is known in the herb garden as bolting quickly if it endures hot and dry conditions for too long. Any prolonged lack of moisture encourages the plant to produce flowers rather than fresh leaves, which will cut your harvesting season depressingly short. A shady position in the garden and regular watering whenever the topsoil feels dry to the touch should help prevent this. 

3. Parsley 

It’s tougher than basil, but parsley also requires moist soil to grow abundantly and taste at its finest. Coarse leaves are a symptom of soil that has been left to dry too long, and the plant will go yellow. Flat-leaf parsley’s quality is also directly related to its hydration, as it’s very productive when it receives regular attention.

Annuals that need extra water during a heatwave 

We adore annuals as bedding plants that flower continuously and so provide our borders with fabulous long-season interest, but this does come at a cost, the cost being that they use an awful lot of water in the process. 

1. Busy Lizzie (Impatiens walleriana)

Renowned for producing masses of cheerful flowers in shady border spots, Busy Lizzie are a stalwart for giving cheerful colour throughout the summer, however, their succulent stems do make them vulnerable to drought and short periods without water can cause the leaves to drop and the flowers to fall, so keep the compost consistently moist, without waterlogging, and if you’re growing your plants in containers, then positioning in light shade will also help to reduce the speed at which the water evaporates.

2. Fuchsia

One of the best plants for hanging baskets, fuchsias do need regular watering to maintain their foliage and their long seasonal interest. Plants will quickly wilt and lose their flowers even before they’ve burst open if there is not adequate moisture in the soil. Whenever you feel the topsoil is dry, give your fuchsia a welcome drink and feed it regularly with a high potash fertiliser from Amazon if you want to encourage more prolific blooming. 

3. Lobelia 

With its utterly transfixing habit and generous profusion of flowers, we love lobelia, yet its fine root system dries out quickly in hot weather, so do not let the compost become dry, as the plant will refuse to flower until it is hydrated again. If you are growing lobelia in hanging baskets or in patio containers, you need to really be watering them once or even twice a day to ensure that they produce their blooms. Trim faded flowers too to encourage fresh growth and another dazzling display.

Shrubs that need extra water during a heatwave 

Many ornamental shrubs are pretty tolerant of long periods of summer heat, but there are a few that require consistently moist soil as they have shallower root systems that can make them more vulnerable to drought than deeper-rooted shrubs.

1. Hydrangeas

Hydrangeas are known for being the most demanding plant in the summer heat as their large leaves lose moisture rapidly through transpiration, and so you’ll look out the window and suddenly see this once magnificent shrub collapsed on the floor. However, they can recover quite quickly if you intervene fast, and so keep the soil very moist and give them at least two long drinks each week. Mulch and compost around the base can also really help to conserve moisture. 

2. Camellias 

I love a spectacular display of camellias in spring, but once summer arrives, if you do not water your camellia, you will risk next year’s flowers suffering, as now is the time that the camellia is developing this year’s buds. They love acidic soil and appreciate long drinks during prolonged dry weather, so keep the soil evenly moist and apply a leaf mould to help maintain both the acidic soil conditions and reduce moisture loss. 

3. Rhododendrons and azaleas

The shallow fibrous root systems really do make it important to monitor rhododendrons and azaleas throughout the heat. If you don’t, a lack of water can cause leaves to curl and droop and edges to scorch, with prolonged drought affecting the formation of the buds that will burst into flower next spring. Allow the water to really saturate the root zone and avoid wetting the foliage, which will help to keep the soil cool. 

I must sound like a stuck record when it comes to the best watering cans to handle all of this additional watering. I swear by Haws, always have, and probably always will. Their watering cans are so beautifully crafted that they are showpieces for your garden in and of themselves. For larger shrubs and borders, I’d go for the two-gallon Warley Fall, which boasts a long spout so that you don’t have to climb all the way into the bed to give your plants a hearty drink.