Red Onion
Allium cepa
Red onions add vivid colour and a milder, slightly sweet flavour to salads, pickles, and roasted vegetable dishes. In the UK, they're most commonly grown from sets (small bulbs) planted in March or April, which is far easier and more reliable than starting from seed. Push sets into well-prepared soil so the tips just show above the surface. Birds love pulling them out, so net newly planted beds until the roots are established. Red onions need a long growing season to size up properly — don't be tempted to harvest too early. Wait until the foliage yellows and falls over naturally in August or September, then lift and dry in the sun for a week before storing. 'Red Baron' is the most popular UK variety with deep red skin and mild, sweet rings. Avoid heavy nitrogen feeding, which promotes leafy growth at the expense of bulb development.
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When to Sow Red Onion
Sow red onion in March, April.
Time to Harvest Red Onion
Expect to harvest approximately 5 months after sowing.
Companion Plants
Expected Yield
Each set produces one bulb; expect 3–4kg per metre of row.
Common Problems with Red Onion
Bolting
Onions bolt (send up a flower stalk) when they experience a cold snap after a warm period, tricking the plant into thinking winter has passed and it should reproduce. Avoid planting sets too early in cold soil, keep plants well watered during dry spells, and choose heat-treated sets labelled as bolt-resistant. Once an onion bolts, use it quickly as it won't store.
White rot
A devastating soil-borne fungus that produces fluffy white mould at the base of the bulb, causing plants to yellow and collapse. There is no chemical cure and the fungal spores persist in soil for 15–20 years. If white rot strikes, avoid planting any alliums (onions, garlic, leeks) in the affected area for at least 8 years and practice strict hygiene with tools and boots.
Neck rot in storage
Grey mouldy decay starting at the neck of stored onions, caused by the fungus Botrytis allii entering through a damp or damaged neck. After lifting, spread onions in a single layer in a sunny, airy spot for 2–3 weeks until the skins rustle and the necks are completely dry and papery. Store in nets or shallow trays in a cool, dry, well-ventilated place — never in sealed bags or damp sheds.
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Cherry Tomato
Solanum lycopersicum var. cerasiforme
Cherry tomatoes are one of the most rewarding crops for UK allotment growers. These small, sweet fruits ripen reliably even in cooler summers, producing heavy trusses from July right through to October. They thrive in grow bags, pots, or directly in the ground, making them versatile for any plot size. Pinch out side shoots regularly on cordon varieties to channel energy into fruit production. Bush varieties like 'Tumbling Tom' need no training and work brilliantly in hanging baskets. Feed weekly with a high-potash tomato feed once the first fruits set. The key to great flavour is letting them ripen fully on the vine rather than picking early.
Beefsteak Tomato
Solanum lycopersicum
Beefsteak tomatoes produce the large, meaty fruits that are perfect for slicing into sandwiches and burgers. They need a long growing season in the UK, so starting seeds early under cover is essential. These are almost always grown as cordons — train them up a single stem, removing side shoots weekly. Each truss produces fewer but much larger fruits than cherry types, often weighing 200–500g each. They benefit from greenhouse growing in cooler regions, though sheltered outdoor spots in the south can produce good results. Consistent watering is critical; irregular watering causes blossom end rot and fruit splitting. Stop the plant at 4–5 trusses to ensure fruits ripen before autumn.
Nantes Carrot
Daucus carota
Nantes carrots are the gold standard for flavour — sweet, crisp, and cylindrical with a smooth skin that barely needs peeling. They perform well in most UK soils but prefer light, stone-free ground to grow straight. If your soil is heavy clay, grow them in raised beds or deep containers filled with sandy compost. Sow thinly to avoid the need for heavy thinning, which attracts carrot fly. Cover rows with fine mesh or enviromesh as a physical barrier against carrot fly — this is far more reliable than companion planting alone. Successional sowing from March to July gives you carrots from June through to winter. Late sowings can be left in the ground over winter under a thick mulch of straw.
Butterhead Lettuce
Lactuca sativa
Butterhead lettuce produces soft, rounded heads with tender, buttery-textured leaves that melt in the mouth. It's one of the quickest salad crops to grow — ready in as little as 8 weeks from sowing. Unlike iceberg types, butterheads tolerate partial shade and are less likely to bolt in warm spells. Sow small batches every 2–3 weeks from March to September for a continuous supply. They work well as an intercrop between slower-growing vegetables like brassicas and leeks. Water consistently but avoid wetting the leaves to reduce the risk of grey mould. 'All the Year Round' is the classic UK variety and lives up to its name, performing well in almost every season.