The crops that cope with a dry spell, and the ones that need the water

A drought-tolerant vegetable is not one that never needs water. It is one that keeps growing through a dry spell, and recovers when the rain returns. The difference matters most in July and August, when a sandy bed can go from damp to dust in a week.

The 20 that cope best

Root crops. Carrots, parsnips, beetroot and turnips have deep or storage roots and need little once established. Carrots are the most reliable of the four; parsnips are slower but equally tough. Water them before the soil dries out completely, not after.

Leaves and stems. Chard is the best leafy crop for dry weather, and it keeps cropping if you pick the outer leaves. Kale and purple sprouting broccoli are tougher than summer cabbage. Leeks and garlic need water to establish, then very little. Among the brassicas, cabbage and calabrese cope better than Brussels sprouts and cauliflower.

Perennials. Asparagus, globe artichoke, Jerusalem artichoke, rhubarb and sorrel all have deep roots or storage organs. Give them water in their first year, then treat them as part of the dry end of the plot. Rhubarb is the least drought-proof of the five and yields better with a spring mulch.

Herbs. Rosemary, thyme, sage and oregano are Mediterranean plants and dislike wet roots more than dry ones. Grow them in a sunny, free-draining spot and water only in the first season.

That is 20 if you count the herbs as four: carrot, parsnip, beetroot, turnip, chard, kale, purple sprouting broccoli, cabbage, calabrese, leek, garlic, asparagus, globe artichoke, Jerusalem artichoke, rhubarb, sorrel, rosemary, thyme, sage, oregano.

The thirsty ones

Lettuce, spinach, celery, celeriac, Florence fennel and radish need consistent moisture. So do cauliflower and Brussels sprouts, which sulk and fail to heart if they dry out. Runner beans need water at flowering; French beans are more forgiving. Peas have poor roots and give a lower yield in drought unless watered.

Onions and shallots are often described as drought-tolerant, and their bulbs store water, but RHS advice is clear that they have poor roots and yields fall in dry soil. Water them at establishment and in very dry spells, and accept a smaller crop if you cannot.

Water the stages that matter

Even a tough crop has a moment when water decides the harvest:

• Establishment. Seedlings and transplants need water until their roots reach deeper soil. This is the one stage where little and often is right.
• Flowering. Peas, broad beans, runner beans, courgettes and sweetcorn all need a soak when flowers and pods are forming.
• Swelling. Potatoes want water every 10 to 14 days once the tubers are marble-sized. Tomatoes, peppers and aubergines want a steady supply once fruit is setting.
• Hearts and heads. Cabbage, calabrese and cauliflower benefit from a soak as the head begins to form.

A deep soak once a week is worth more than a daily sprinkle. When to water vegetables has the amounts and timing.

Plan the plot around water

Put the thirstiest crops together, near the tap or the water butts, so you are not carrying cans across the whole plot. Put roots, perennials and herbs at the far end. Use mulch on every bed, and keep the dry end mulched more thickly.

If a hosepipe ban arrives, the same plan still works with cans and butts. Hosepipe bans and allotments covers the rules.

What not to expect

Drought-tolerant crops survive; they do not necessarily crop heavily. A carrot that never gets water will be smaller and may split when rain finally arrives. A parsnip will be woody. A chard plant will recover, but the leaves will be tougher.

The honest approach is to grow more of the tough crops, water the ones that repay it, and accept a smaller harvest from the rest. That is a better use of water than trying to keep a full lettuce bed going through August.

For the wider picture, see growing vegetables in a changing climate.