Summer Vegetable Garden: What to Grow and When

A productive summer vegetable plot in the UK isn't built in July — it's planned in late winter and steadily planted from March through June. This guide walks through the vegetables that actually earn…

A productive summer vegetable plot in the UK isn't built in July — it's planned in late winter and steadily planted from March through June. This guide walks through the vegetables that actually earn their space in a British summer garden, the months to sow and transplant them, and the small jobs that make the difference between a glut and a disappointment.

Why timing matters (and when to start)

British summers are short, cool, and inconsistent. The difference between a tomato harvest in August and a wash of blight in the same month usually comes down to whether plants were out early enough to fruit before disease pressure peaks. The core rule: get cool-season crops in the ground as soon as the soil is workable (usually March–April in the south, late April further north), and hold warm-season crops (tomatoes, peppers, courgettes, sweetcorn, beans) until the last frost has passed — typically mid-May in the south, late May to early June in Scotland and the north.

Use the soil temperature, not the calendar, for warm-season sowings. Courgettes and French beans sulk below 13 °C; sweetcorn refuses to germinate under 12 °C. A cheap soil thermometer takes the guesswork out.

What you'll need

• A sunny spot — at least 6 hours of direct sun between April and September. South or west-facing is ideal.
• A bed or border with drainage. A 1 m × 3 m strip is enough for a starter summer veg patch.
• Two bags (roughly 40 litres each) of peat-free multi-purpose compost for containers and seed-sowing.
• One 50-litre bag of well-rotted manure or garden compost per square metre of bed, forked into the top 20 cm.
• A simple seed-sowing kit: modular trays, labels, a watering can with a fine rose, and a fleece or cloche for late frosts.
• For tomatoes, peppers, and aubergines: a greenhouse, polytunnel, or a sunny sheltered wall — outdoor tomatoes are a gamble north of Manchester.
• A notebook or phone reminder: a fortnightly sowing calendar stops you from missing succession sowings.

The crops and when to start them

March to early April — the first outdoor sowings

Sow direct once the soil is workable and not waterlogged: broad beans, early peas, spinach, radish, spring onions, and the first carrots and beetroot. These cool-season crops germinate at 7–10 °C and tolerate a light frost.

• Broad beans: sow 5 cm deep, 20 cm apart in double rows 30 cm apart. Pinch out the growing tips once the first pods set to deter blackfly.
• Peas: sow in a flat-bottomed drill 5 cm deep, 5 cm apart, with a cane or twiggy support 1.2 m tall for taller varieties.
• Carrots and beetroot: thin to 5–8 cm apart. Carrot fly is active from late May — cover with fleece or 60 cm-high mesh barriers from sowing if you've had trouble before.

April — get ahead indoors

Sow tomatoes, chillies, peppers, and aubergines indoors at 18–21 °C in modules or 9 cm pots. Prick out into individual pots once the first true leaves appear. Harden off for 7–10 days before planting out: a cold frame or a sunny doorstep with fleece is ideal.

Sow courgettes, marrows, pumpkins, and sweetcorn indoors in mid-April in 7 cm pots, one seed per pot, on their side to prevent rot.

May — the big planting window

After the last frost (mid-May in the south, late May in the north), plant out:

• Tomatoes 50–60 cm apart, with a 1.5 m cane for cordon varieties. Pinch out side-shoots weekly.
• Courgettes 90 cm apart in soil enriched with compost. One plant feeds a family of four; two plants will swamp you.
• Sweetcorn in blocks, not rows, 45 cm apart each way. Wind-pollinates badly in single rows — you need at least a 3 × 3 grid for proper cobs.
• French and runner beans once the soil is 13 °C. French beans 15 cm apart in rows 45 cm apart; runner beans need a 2 m wigwam or cane row.
• Brassicas for autumn (calabrese, kale, purple sprouting, winter cabbage) — transplant 45–60 cm apart into firm ground. Net against pigeons and cabbage white butterflies the moment you plant.

June and July — successions and warmth-lovers

Sow a second batch of French beans, salad leaves, radish, and carrots in June for an August–September harvest. Direct-sow Florence fennel, spring cabbage, and overwintering onions in July for next year's store-cupboard.

Sow pak choi, mizuna, and other oriental leaves in late July for autumn salads — they bolt if sown earlier.

Common mistakes to avoid

• Planting out too early. Courgettes and tomatoes killed by a single May night frost undo weeks of indoor work. Watch the forecast, keep fleece handy.
• Skipping the hardening-off week. Plants raised at 20 °C and dumped into 12 °C winds stop growing for two weeks. Build up outdoor time gradually.
• Crowding sweetcorn and courgettes. Both need airflow to pollinate well and resist mildew. The spacings in the lists above are minimums, not suggestions.
• Forgetting to feed. Courgettes, tomatoes, and sweetcorn are hungry. A liquid tomato feed (high in potash) every 10–14 days once flowers appear makes a visible difference.
• Ignoring the first signs of blight. Brown patches on tomato leaves in damp July/August weather should trigger immediate removal of affected leaves and a 14-day spray of Bordeaux mixture if the forecast stays wet. If it spreads, lift the plants to save the rest of the plot.
• Letting brassicas go unprotected. A pigeon can strip a row of brassicas in an hour. Net the moment you plant — not when you see the damage.

Troubleshooting quick reference

• Tomato flowers dropping without setting — usually night temperatures below 12 °C or above 24 °C, or dry compost. Mist the flowers in the morning and water more consistently.
• Courgettes rotting at the tip — inconsistent watering or poor pollination. Water deeply twice a week rather than daily, and plant a second courgette nearby to improve pollination.
• Carrot seedlings vanishing — slugs or carrot fly. Use fleece from sowing and water in the morning so the foliage is dry by evening.
• Yellowing brassica leaves with whitefly clouds — yellow sticky traps and a forceful weekly hose-down. For heavy infestations, a spray of insecticidal soap at dusk.
• Sweetcorn cobs with missing kernels — poor pollination. You needed a block, not a row. Next year, plant in a 4 × 4 square.

A simple summer plan

For a 10 m² bed worked by one person, plan it like this:

• March: broad beans down one side, peas down the other, spinach and radish in the middle.
• Late May: replace spent broad beans with French beans, replace spinach with courgettes, plant tomatoes against a south wall.
• June: sow a second row of French beans and a late batch of carrots between the tomatoes.
• July: underplant the tomatoes with a single basil each, and sow pak choi where the early peas finished.

By late August you should be cropping tomatoes, courgettes, French beans, carrots, and beetroot; by October, the last French beans, pumpkins, and autumn calabrese. That single bed delivers roughly 80–100 kg of vegetables across the season if you keep on top of the sowings.

Final tips

• Mulch with straw or grass clippings in June to lock in moisture during July heatwaves — a 5 cm layer cuts watering by half.
• Water in the morning, not the evening, to reduce slug and disease pressure.
• Save seed from one open-pollinated variety each year (a French bean is easiest). It's free, and over four years you'll have a strain adapted to your plot.
• Keep a sowing diary. Next January you'll thank yourself when you can see exactly when last year's tomatoes went in and how they cropped.