Why a British summer needs a little forward planning

Tomatoes are tropical by nature. They want warmth, long bright days and steady moisture, and a British summer can offer all three one week and none of them the next. That is not a reason to give up on them – it is simply a reason to treat them as a crop you manage carefully rather than one you scatter and forget about.

The good news is that tomatoes are extraordinarily generous when you get the basics right. Two or three well-grown cordon plants in a sunny border, a greenhouse or even a large pot by the back door can keep a household in salad tomatoes from July to October, with a glut in late August for chutney and passata. The trick is to work with the climate rather than fighting it: choose varieties that ripen reliably in a shorter season, start them early indoors, and only plant them out when the weather has genuinely turned.

Choosing varieties that earn their keep

In a cool, changeable climate, variety choice matters more than anything else you do. Seed catalogues aimed at warmer countries will tempt you with huge beefsteaks that need a long, hot summer; in most of the UK they will sulk, split, or produce a handful of green fruits in September. Look instead for the words early, cold-tolerant or blight-resistant in the description, plus a stated ripening time of around 60 to 75 days from planting out.

Reliable choices for outdoor growing include classic bush varieties such as Gardeners' Delight for sweetness and heavy trusses, Shirley for an early, dependable crop, and Moneymaker for solid, all-purpose fruit. If blight is a recurring problem on your plot – and in wet western areas it often is – then modern blight-resistant varieties are genuinely worth the extra cost of seed. They taste better than their reputation suggests.

Growing under glass, in a polytunnel, or against a warm south-facing wall widens your options considerably. There you can chance the larger beefsteak types and the heritage varieties with their extraordinary colours and flavours. Choose a mix:

• Two or three early varieties for a reliable first crop in July
• One or two maincrop varieties for bulk through August and September
• One blight-resistant variety if you garden in a damp or western location
• Cherry types for children, snacking and containers, which ripen fastest of all

Starting your seed indoors

Sow indoors from late February in the south, or mid-March further north and in Scotland. A bright windowsill is workable, though seedlings will stretch towards the light and become leggy. A heated propagator or a sunny porch gives you much stockier plants, and a simple fluorescent or LED grow light is a worthwhile investment if you plan to grow more than a handful.

Sow into small pots or modules filled with seed compost, pressing the seed no more than 6mm deep. Water gently and keep the compost at around 18–21°C. Germination usually takes 7–14 days. As soon as the seedlings are up, move them into cooler, brighter conditions – around 15°C – to keep growth compact.

Prick out the seedlings into individual 9cm pots once they have their first pair of true leaves, burying the stem slightly deeper than it was growing. Roots will form along the buried stem and give you a sturdier plant. Pot on again into 12–15cm pots as the roots fill the space, and keep them going on a windowsill or in a frost-free greenhouse until planting time.

Hardening off and planting out

This is the stage where British gardeners lose the most plants. Tomato foliage is damaged by temperatures below about 10°C, and a single late frost will finish them outright. Do not be fooled by a warm spell in early May.

Find your local last-frost date and treat it as a guide, not a guarantee. In sheltered coastal Cornwall that may be late April; in inland Scotland and northern England it can be early June. When you are confident, harden the plants off over 7–10 days: move them outside during the day and back under cover at night, gradually extending the time until they stay out around the clock.

Plant into a sunny, sheltered spot – ideally against a south or west-facing wall, which stores heat and keeps the plants a degree or two warmer overnight. Improve the soil with well-rotted compost and a handful of general-purpose fertiliser. Space cordon varieties 45–60cm apart and bush types a little wider, and water them in well. If you are growing in pots or gro-bags, use a good peat-free multipurpose compost and stand the containers against the warmest wall you have.

Watering, feeding and training through summer

Irregular watering is the single biggest cause of split fruit and blossom end rot. Aim for consistent moisture rather than soaking and drying out, and water in the morning, at the base of the plant, keeping foliage as dry as possible to reduce disease.

Once the first truss of flowers has set fruit, begin feeding with a high-potassium tomato feed every week or fortnight. Too much nitrogen-rich feed and you will get magnificent foliage and very few tomatoes.

Cordon (indeterminate) varieties need training up a cane or string, with side shoots pinched out where the leaf joins the main stem. Bush varieties are left to do their own thing. Either way:

• Pinch out the growing tip of cordon plants in late summer to concentrate energy into ripening existing fruit
• Remove leaves below the first truss once fruit has set, to improve airflow
• Tap the flowers gently on a still day, or leave the door of the greenhouse ajar, to help pollination
• Keep an eye out for blight in warm, humid spells – brown patches spreading from the leaf tips are the warning sign

Ripening the last of the crop

By late September, outdoor plants start to slow. Remove any remaining flowers, which will not have time to set and ripen, and thin out some foliage so light reaches the fruit. If blight strikes, strip healthy fruit immediately, wipe it clean and ripen it indoors.

Green tomatoes will ripen on a sunny windowsill or in a drawer with a ripe banana, which releases ethylene and speeds the process up. Anything that refuses can be turned into green tomato chutney, fried in slices, or made into a sharp, tangy relish that will keep you going through the winter. Grow a few plants well and you will wonder why you ever bought them.