Allium cepa 'Ailsa Craig' is a Hardy Annual and one of Britain's most celebrated and long-standing onion varieties, introduced in the 1880s and still considered a benchmark of excellence for both the exhibition bench and the kitchen garden. It is a long-day onion, triggering bulb development in response to the lengthening days of British late spring — perfectly calibrated to our growing season when sown at the correct time.

The Flavour Difference: 'Ailsa Craig' is notably milder and sweeter than most standard brown onion varieties — a characteristic that comes from a lower concentration of the sulphurous compounds responsible for the sharp, pungent flavour of typical cooking onions. This makes it far more pleasant to handle and eat raw, and gives it a gentle, sweet quality when cooked that is particularly valued in French onion soup, onion tarts, and slow-cooked casseroles where the onion's flavour needs to come forward rather than fade into the background.

Exhibition Heritage: 'Ailsa Craig' has been winning prizes at horticultural shows across the British Isles since the late Victorian era, and it remains the variety of choice for competitive vegetable growers entering the "heaviest onion" class. The combination of genetics and a long growing season from an early January sowing can produce bulbs of truly impressive size — seasoned exhibitors have grown specimens well in excess of 1kg from seed. For the kitchen gardener, even a modestly sized 'Ailsa Craig' bulb is noticeably larger and more handsome than anything grown from sets.

Cooking Qualities: The low sulphur content that gives 'Ailsa Craig' its gentle raw flavour also means it caramelises to a deeper, more complex sweetness than sharper varieties when cooked slowly over low heat. The flesh is notably juicy and almost translucent when sliced, making it outstanding for dishes where the onion is the star rather than the supporting act — French onion soup, pissaladière, tarte Tatin d'oignons, and simple roasted whole onions with thyme and butter all benefit dramatically from the quality of this variety.

'Ailsa Craig' is best sown early and given a long season — the size and quality of the final bulb is directly related to how much growing time the plant accumulates before bulbing begins in early summer.

How to Sow:
For the largest bulbs, sow indoors from late December to late February — the earlier the better within this window. Sow 2–3 seeds per module approximately 1cm deep in good-quality seed compost and thin to the strongest seedling. Maintain a temperature of 10–15°C — onions prefer cooler germination conditions than most vegetables, and warmth above 20°C can suppress germination significantly. Seedlings emerge within 10–14 days. Grow on in a cool, bright spot such as an unheated greenhouse or well-lit cold frame — sturdy, cool-grown seedlings transplant and establish far better than soft, drawn ones.

Transplanting:
Plant out from March to April once seedlings are pencil-thick at the base — the classic "pencil stage" that indicates the plant is ready to go into its final position. Space plants 10cm apart in rows 25–30cm apart for standard bulbs, or 20–25cm apart if aiming for exhibition-sized specimens. Firm soil well around the base of each transplant. A well-prepared bed with good general-purpose fertiliser incorporated at planting will support the long growing season ahead.

Ongoing Care:
Keep the bed consistently weed-free — 'Ailsa Craig' is not an aggressive grower and cannot compete with established weeds, which will significantly reduce final bulb size. Water regularly during dry spells in May and June when the bulbs are beginning to swell, but taper off watering from mid-July onwards to allow the outer skins to ripen and dry properly. Avoid high-nitrogen feeds once swelling begins, as these encourage lush, soft growth that stores poorly and is prone to neck rot.

Harvesting & Storing:
Bulbs are ready to harvest from August to September when the foliage yellows and falls naturally. Lift carefully with a fork on a dry day and lay in a single layer on wire racks or slatted trays in a warm, airy spot to cure for at least two to three weeks. 'Ailsa Craig' stores for a somewhat shorter period than harder-skinned varieties — typically 2–3 months — so use it before your harder-storing onions and plan accordingly. Its exceptional flavour more than compensates for the shorter storage window.

'Ailsa Craig' is a slow, steady grower that occupies its bed from March through to September — these companions from our range make the most of the space around it while actively benefiting the crop:

• 🧡 Calendula 'Art Shades Mixed': The Potager Companion. Calendula is one of the most reliable and versatile companions in the kitchen garden and works beautifully alongside a long-season onion crop like 'Ailsa Craig'. Its sticky roots deter soil pests and nematodes that damage developing bulbs below ground, while its continuous flowers sustain a population of beneficial hoverflies and lacewings above ground throughout the summer. The warm apricot and cream tones of Art Shades look genuinely beautiful edging the onion bed, softening the geometric rows of glaucous onion foliage with colour and movement from June right through to October.
• 🌼 Borage: The Biodiversity Builder. Borage is a superb general-purpose kitchen garden companion and particularly well suited to the long growing season of 'Ailsa Craig'. Its deep taproot mines soil nutrients that benefit the shallow-rooted onion crop, and its sustained flowering from June to October provides high-value nectar for bees and beneficial insects across the entire growing season. Planted at the ends of the onion rows, Borage creates a lively, living boundary that benefits every crop in the vicinity — and a single sprig of its edible blue flowers floating in a glass of summer Pimm's alongside a freshly sliced 'Ailsa Craig' salad is a quietly perfect combination.
• 🌼 Nasturtium 'Tom Thumb': The Compact Bodyguard. Nasturtiums are a classic and well-evidenced companion for alliums — their pungent foliage is widely believed to deter onion fly, which lays its eggs at the base of developing plants and whose maggots can devastate a crop. As a trap crop for blackfly, they draw pest pressure away from the valuable developing bulbs. The compact, mounding habit of Tom Thumb means it fills the spaces between onion rows and path edges without ever competing with the crop, and the bold orange and red flowers bring vivid colour to the productive garden from early summer through to the first frosts.
• 🌿 Basil Classic Italian: The Kitchen Garden Classic. The aromatic oils of Basil are believed to deter the aphids and thrips that target allium foliage, making it a useful near-neighbour in the potager bed. On the plate, the pairing of 'Ailsa Craig' and fresh basil is exceptional — the sweetness and gentleness of this onion variety is the perfect foil for basil's intensity, and together they form the backbone of a classic Italian salad, bruschetta topping, or slow-cooked tomato sauce that neither ingredient could achieve alone quite as well.

Sow as early as late December for the longest possible growing season — the more weeks 'Ailsa Craig' has before the days begin to lengthen, the larger and more impressive the final bulb will be.