Allium cepa 'Red Baron' is a Hardy Annual and one of Britain's most popular and consistent red onion varieties. It is a long-day onion, meaning it requires the lengthening days of late spring and early summer to trigger bulb formation — making it perfectly adapted to the British growing season when sown at the correct time.

Seeds vs Sets: Growing 'Red Baron' from seed rather than sets offers several meaningful advantages. Seed-grown plants establish a stronger root system, are significantly less prone to bolting, and have better resistance to onion white rot and neck rot. Seed-grown bulbs also tend to store for longer once harvested — a particularly important advantage with red onions, which are naturally shorter-storing than white varieties when grown from sets. The longer growing season required from seed is a small investment for a noticeably superior result.

The Colour Chemistry: The rich red-purple pigmentation of 'Red Baron' comes from anthocyanins — the same antioxidant compounds found in red wine, blueberries, and beetroot. These pigments are concentrated in the outer skin and the flesh layers immediately beneath it, giving the bulb its characteristic concentric rings of deep purple and white when sliced. The colour is water-soluble and bleeds beautifully into dressings, pickling liquors, and cooking juices, making 'Red Baron' as visually dramatic in the kitchen as it is in the garden.

Potager Value: Onions in general are among the most structurally satisfying vegetables in the kitchen garden — their tall, cylindrical, blue-grey foliage contrasts beautifully with the broader leaves of squash and salad crops. 'Red Baron' adds an extra dimension as the season progresses, with the deep burgundy shoulders of the swelling bulbs visible above the soil from July onwards, creating a rich colour accent in the productive garden.

Growing onions from seed requires a little more patience than sets, but the process is straightforward and the results are consistently superior — larger bulbs, better storage life, and lower disease risk.

How to Sow:
Sow indoors from late January to mid-March into module trays or seed trays of good-quality seed compost. Sow 2–3 seeds per module approximately 1cm deep and thin to the strongest seedling. Maintain a temperature of 10–15°C — onions prefer cooler conditions for germination than most vegetables, and excessive warmth can inhibit germination. Seedlings typically emerge within 7–14 days. Grow on in a bright, cool spot such as an unheated greenhouse or cold frame, as stocky, cool-grown seedlings establish far better than soft, warm-grown ones.

Transplanting:
Plant out from March to April once seedlings are approximately 15–20cm tall and pencil-thick at the base — a stage known as the "pencil stage." Space plants 10cm apart in rows 25–30cm apart. Firm the soil well around each transplant to anchor the roots, but avoid burying the base of the stem. A well-prepared bed enriched with general-purpose fertiliser at planting time will serve the crop well throughout its long growing season.

Ongoing Care:
Keep the bed weed-free throughout the season — onions are poor competitors and a weedy bed significantly reduces final bulb size. Water during dry spells in early summer when bulbs are swelling rapidly, but reduce watering in July and August to help the outer skins ripen and harden properly. Avoid high-nitrogen feeds once bulbs begin to swell, as these encourage lush foliage at the expense of firm, well-coloured bulbs.

Harvesting & Storing:
Bulbs are ready to harvest from July to September when the foliage begins to yellow and topple naturally. Lift with a fork on a dry day and leave on the soil surface or on wire racks in a warm, airy spot to dry and cure for 2–3 weeks. Once the necks are completely dry and papery, store in nets, trays, or braided strings in a cool, dry, frost-free place. Properly cured 'Red Baron' will store for 3–4 months.

'Red Baron' is one of the great alliums — and alliums are some of the most beneficial plants in the kitchen garden, actively protecting their neighbours. These companions from our range work with the crop and look beautiful doing it:

• 🧡 Calendula 'Art Shades Mixed': The Potager Partnership. Calendula is one of the most consistently valuable flowers in the kitchen garden and pairs exceptionally well with onions. Its resin-coated roots deter soil nematodes and wireworms that can damage developing bulbs, while its flowers attract the beneficial hoverflies and lacewings whose larvae prey on thrips and aphids — two of the onion's principal above-ground pests. The warm apricot and cream tones of Art Shades create a genuinely beautiful colour contrast alongside the deep burgundy shoulders of swelling 'Red Baron' bulbs as summer progresses.
• 🌼 Borage: The Biodiversity Builder. Borage is one of the great all-round kitchen garden companions and works particularly well alongside alliums. Its deep taproot mines nutrients from lower soil layers, making them available to the shallow-rooted onion crop, and its prolific electric-blue flowers sustain a constant presence of beneficial insects throughout the summer. Planted at the ends or edges of the onion bed, a generous clump of Borage creates a lively, pollinator-rich boundary that benefits every crop in the vicinity — and the edible flowers make a striking garnish alongside a Red Baron salad.
• 🌼 Nasturtium 'Tom Thumb': The Pest Decoy. Nasturtiums are a classic allium companion — their pungent foliage is widely believed to confuse and deter onion fly, one of the most damaging pests of the onion family, while their compact habit means they fill the spaces between rows without ever competing seriously with the crop. As a trap crop for blackfly and aphids, they keep pest pressure away from the developing bulbs. And come harvest time, their peppery leaves and vivid flowers sit beautifully alongside thinly sliced 'Red Baron' in a summer salad bowl.
• 🌿 Basil Classic Italian: The Italian Kitchen Garden. Basil and onion are one of the great culinary partnerships — and growing them side by side is entirely practical. Basil's aromatic oils are believed to deter the aphids and thrips that target onion foliage, while its presence in the kitchen garden means that the two finest ingredients in a classic Italian dressing, bruschetta, or pasta sauce are ready to harvest simultaneously from the same bed. A row of 'Red Baron' alongside a pot of basil is one of the most satisfying and productive small-space kitchen garden combinations there is.

Sow indoors in late winter for transplanting in spring — then watch the deep burgundy bulbs swell through summer for a glorious July to September harvest with months of storage ahead.