Liz’s Allotment Life: How crops are coping with a heatwave

Heatwaves are revealing a lot about what works – and what doesn’t – on my allotment. With water in short supply and temperatures staying high, I’ve been watching closely to see which crops are managing to keep growing, which are showing signs of stress and where a little extra water makes the biggest difference.

There have been some surprises. A few crops I expected to struggle are flourishing, while others that normally seem unfussy are showing the effects of prolonged dry weather. It’s also been a useful reminder that how a plant responds to heat depends not just on the weather, but on the crop, how established it is and where it is growing.

Climbing beans growing on the allotment during a prolonged period of hot, dry weather, with flowering plants still producing despite the challenging conditions

At a glance: how the allotment is coping

• Cucumbers and tomatoes – thriving with regular watering 
• Sweet potatoes – benefiting from warm soil 
• Winter squash – producing despite limited watering 
• Established
  Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs.

  perennial crops – coping well so far 

Struggling in the heat and drought

• Climbing beans – reduced pod set 
• Spring onions – yellowing and wilting foliage 
• Beetroot – afternoon wilting

The Successes

Cucumbers and tomatoes

These are undeniably thriving in the heat, as long as I get enough water to them with my watering can. I expected these crops to do well, and I’m pleased that is the case. A lot of the more tender crops are doing well this summer, including sweet potatoes, which are benefiting from warm soil. The important thing is keeping these fast-growing, fruiting crops supplied with enough moisture while they are actively producing.

Winter squash

I have not watered these at all since the hosepipe ban came in a few weeks ago and I’m pleased to see them flourishing. The odd fruit has dropped off early – I think due to stress, an abiotic response where plants shed young fruit to conserve water – but there are still plenty there. My squashes are growing in a shadier bed on the allotment simply because that was the space I had, and I wonder whether the reduced exposure is helping to limit heat and water loss.

Winter squash plants thriving in a shady area of the allotment despite weeks of hot, dry weather

Skirret

This is a perennial crop and was a new introduction to the plot this year. As with the squash, I have not watered it for several weeks, but it’s still flowering and looking lush and abundant. I would mainly expect the benefits of a perennial crop, including an established root system, to become more apparent after a year or so. Established

Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs.

Skirret in full flower on the allotment, where the established perennial is continuing to grow vigorously despite several weeks without additional watering

Strawberries

Despite the mice getting all my fruit, the plants are looking really healthy and sending out lots of runners. They have been in the ground for a couple of years now, and their established root networks seem to be thriving without me needing to water. They have all finished fruiting, and any fruit that is trying to crop through this heatwave is more likely to struggle as the plants come under additional water and heat stress.

The Struggles

Climbing beans

While I only grow French beans, climbing beans are generally more reliable in a heatwave than runner beans. They are cropping but are nowhere near as abundant as at other times, as high temperatures restrict overall pod set. 

Beetroot

The roots themselves are a good size, but the foliage wilts dramatically every afternoon. Beetroot is relatively drought-tolerant once established, but prolonged dry spells can still cause stress. I’m watering them about once a week to keep them going. They are a staple of my autumn and winter diet, but without a cool pantry or cellar to store them in, harvesting early isn’t really an option, so I’m hoping they will hold until the weather cools.

Spring onions

While these grew very well earlier in the season, the lack of moisture is showing in the yellowing and wilting leaves. Onions have relatively poor root systems, so they can struggle during drought unless they are watered. I just need to try and eat them before secondary decay sets in and they are only fit for compost.

Raspberries

I never water these on principle, and as they are so vigorous I have no doubt the plants will survive. The only water they have had for several years is rainfall, and this year they are about two-thirds the height of previous years due to water deficit. However, they are starting to crop so I am not worried about them in the long-term.

Established raspberry canes producing a crop despite reduced growth after a prolonged period of hot, dry weather, with no additional watering for several years

Key takeaways for future hot summers

• Tender crops can thrive in hot weather, provided they have enough moisture while flowering and fruiting
• Some shade can help reduce heat and water stress, although most fruiting crops still need plenty of light
• Established plants can be much more resilient to dry conditions than newly planted or establishing crops
• When water is scarce, prioritise crops that are flowering, fruiting or forming edible parts, to make the most of every watering can

Crop of the week: cucumbers

I just can’t keep up with eating them! I’m watering them two or three times a week and they are thriving. I am growing four plants, two ‘Marketmore’, a ridge cultivar, and two ‘Crystal Lemon’, an heirloom type, and this is by far the best year I can remember for growing them outdoors in the UK. 

I don’t bother with fancy recipes; I just chop them up and add them to summer salads on warm evenings.

Coming up on the plot

Watering, watering and more watering. Directing water with a watering can to where the roots need it is by far the most time-consuming task at the moment.

Weeding is light at the moment, as the dry conditions are suppressing much of the weed growth, and I am holding off on any new seed sowing or planting until temperatures drop, as young

A seedling is a young plant grown from seed.