How to Grow Onion
'Red Baron' from Seed
The definitive red storage onion -- RHS AGM confirmed twice; deep crimson-blood-red skin with beautiful concentric red and white rings when sliced; firm semi-globe bulbs with excellent storage potential (6-9 months -- until the following crop); deeper more pungent flavour than Ailsa Craig; superb raw in salads, roasted, caramelised, or pickled cerise-pink; sow January-February for exhibition or March-April for a kitchen crop; thin to 10cm; harvest August-September; cure thoroughly for maximum storage life
Onion 'Red Baron' is the red onion that the RHS has awarded its highest garden performance recognition (the Award of Garden Merit, confirmed in both 2005 and re-confirmed in 2013), and it earns that recognition with consistent, reliable performance that makes it the standard choice for UK gardeners growing red onions from seed. The deep crimson-blood-red skin with its semi-globe form is visually striking in the kitchen garden, and the sliced bulb reveals something even more attractive: concentric rings of vivid dark red and clean white that make horizontally-sliced Red Baron a genuinely beautiful addition to a salad bowl or a charcuterie board.
The contrast with the other main onion in the Bishy range -- Ailsa Craig -- could not be more instructive. Where Ailsa Craig is a sweet, mild, fresh-eating onion with minimal storage life (1-2 months maximum), Red Baron is a firmer, more flavourful variety with excellent storage potential. With good skins and characteristically thin necks after curing, properly stored Red Baron will keep until the following year's crop is ready to harvest -- providing nearly year-round onion supply from a single spring sowing. The two varieties complement each other perfectly: Ailsa Craig for the fresh summer kitchen, Red Baron for the stored winter pantry.
Quick Facts at a Glance
Plant Type
Hardy Annual vegetable -- RHS AGM; the UK's definitive red storage onion
Bulbs
Deep crimson skin; concentric red and white rings when sliced; semi-globe; firm
Storage
Excellent keeper -- good skins, thin necks; stores until the following crop
Flavour
Deeper, more pungent than Ailsa Craig; excellent raw in salads and roasted
Sow
Jan-Feb indoor for exhibition; March-April general crop; harvest Aug-Sept
Difficulty
2 out of 5 -- patient sowing; the reward is months of beautiful red onions
Understanding Red Baron
RHS Award of Garden Merit -- Twice Confirmed
The RHS AGM for Red Baron was first awarded in 2005 and then reconfirmed following additional trials in 2013 -- a double confirmation that demonstrates the variety's consistent performance across changing UK growing conditions and over an extended evaluation period. The reconfirmation in 2013 is particularly significant because it indicates that performance did not decline with further observation, a test that some initially-impressive varieties fail when subjected to longer-term scrutiny. Red Baron has demonstrably performed well over many years of UK growing trials.
Storage Onion vs. Fresh Onion -- The Critical Distinction
The characteristic that most distinguishes Red Baron from fresh-eating varieties like Ailsa Craig is storage potential. Red Baron's higher sulphur content (which produces the characteristic deeper, more pungent flavour) also provides the chemical preservative that extends storage life significantly. With proper curing and storage in cool, dry, well-ventilated conditions, Red Baron bulbs in good condition typically store for 6-9 months -- potentially well into the following spring or even until the new season's crop is ready. This transforms a summer harvest into a near-year-round kitchen resource from a single sowing.
The Red and White Rings -- Visual and Culinary Significance
The characteristic concentric rings of deep red and clean white that appear when a Red Baron bulb is sliced horizontally are both visually striking and an indicator of quality: well-grown, properly developed Red Baron produces clear, well-defined rings with the colour reaching deep into the flesh. Pale, washed-out rings indicate insufficient sunshine during the growing season or overly rich, wet soil conditions. The visual quality of the rings makes Red Baron the natural choice for any presentation where the cut surface is visible: thinly-sliced raw in salads, roasted halved beside steak, or pickled whole in white wine vinegar where the red pigment colours the pickling liquid attractively.
Sowing & Growing On
Sow January-February (Exhibition) or March-April (Kitchen Crop) -- Thin to 10cm -- Harvest August-September
Sow indoors in seed trays at 10-15°C from January (exhibition) or March-April (kitchen crop). Cover 1cm deep. Germination 10-14 days. Grow on in cool conditions. Plant out pencil-thick seedlings at 10cm spacing. Harvest August-September when tops begin to yellow and fall. Cure thoroughly for maximum storage.
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Sow indoors in January-February (for largest exhibition bulbs) or March-April (for excellent kitchen onions). Sow thinly in seed trays or modules at 1cm deep. Maintain 10-15°C -- onions germinate better in cooler conditions than many vegetables. Germination 10-14 days. Grow on in maximum available light in cool conditions to avoid leggy, weak seedlings.
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Plant out pencil-thick seedlings from March (exhibition) or April-May (kitchen). Rich, moist, free-draining soil in full sun. Space 10cm apart for standard kitchen bulbs; 15cm for larger bulbs. Set just below the soil surface with the base 1cm deep. Do not plant in freshly manured soil -- incorporate compost the previous autumn instead. Water in well.
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Water only in dry spells; weed regularly. Onions compete poorly with weeds -- keep the bed weed-free from planting until harvest. Water only during genuine dry periods (more than 2 weeks without significant rain) and stop watering completely when the tops begin to fall over, allowing the skins to firm up and dry in preparation for storage.
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Harvest when tops yellow and fall; cure for 2 weeks before storing. When tops begin to yellow and fall (typically August-September), choose a dry day to loosen bulbs with a fork and pull. Lay in a single layer in full sun for 1-2 weeks (or in a warm, well-ventilated greenhouse if weather is wet). The skins should be papery-dry and the necks completely dry before storage. Store in net bags or on slatted shelves in a cool, airy location and check weekly.
Growing On & Care
Raw in Salads -- The Visual Impact
Red Baron sliced horizontally into thin rings provides one of the most visually striking salad ingredients available from a kitchen garden: the concentric deep red and white rings are precisely the combination of colour and pattern that elevates a simple salad from functional to beautiful. Slice as thinly as possible (a mandoline or very sharp knife) for the most delicate presentation. Soak sliced rings in cold water for 20 minutes before serving to reduce the raw pungency slightly while retaining the colour and texture. The red pigment (anthocyanin) is water-soluble and will bleed slightly into a dressing -- this is visually attractive in clear dressings but may be managed by adding the rings last in creamy or white dressings.
Roasted and Caramelised
The deeper, more pungent flavour of Red Baron transforms beautifully under heat: the sulphur compounds that make raw Red Baron more assertive than Ailsa Craig are volatilised by cooking, leaving behind the natural sugars in a more concentrated form. Halved Red Baron roasted alongside chicken or beef becomes caramelised, sweet, and deeply savoury simultaneously. Quartered and slow-roasted in olive oil with thyme and balsamic vinegar for 40 minutes at 180°C, the rings collapse into jammy, intensely flavoured layers. French onion soup made with Red Baron has a richer colour and deeper flavour than white onion equivalents.
Pickled Red Onions
Red Baron is arguably the finest pickling onion available from the UK kitchen garden. Sliced into thin rings and pickled in white wine vinegar with salt, sugar, and whole black peppercorns for 24-48 hours (quick pickle) or 2-3 weeks (traditional pickle), Red Baron produces the vivid cerise-pink pickled onion that has become a restaurant staple as a garnish for tacos, burgers, pulled pork, avocado dishes, and cheese boards. The anthocyanin pigment that gives Red Baron its dark red colour reacts with the acidity of the vinegar to produce the characteristic bright pink that makes pickled Red Baron so visually distinctive.
The Storage Advantage -- Year-Round Onions
The storage potential of Red Baron is its most practical kitchen advantage. A successful crop sown in March and harvested in August, properly cured and stored, provides kitchen onions until late spring of the following year -- effectively year-round supply from a single growing season. The good-skin, thin-neck characteristics that contribute to storability are also indicators of well-grown, well-cured bulbs: good skins (several layers of papery outer skin rather than thin or damaged covering) protect against moisture loss and mould; thin, completely dried necks prevent bacterial entry through the neck that is the most common cause of storage rot in onions.
Companion Planting -- Onion Fly and Carrot Fly Deterrence
The same principles of companion planting that apply to Ailsa Craig apply equally to Red Baron: grow mint near the onion bed to mask the onion scent that onion fly (Delia antiqua) uses to locate egg-laying sites; interplant with carrot rows to provide the allium scent that disrupts carrot fly location. A mixed row of Red Baron and carrots is a classic kitchen garden companion combination that provides mutual pest deterrence. The visual contrast of the dark red onion foliage alongside the feathery carrot top is also attractive.
Health Benefits -- The Anthocyanin Advantage
The dark red colour of Red Baron is produced by anthocyanins -- the same family of pigments that make blueberries, red cabbage, and raspberries nutritionally distinctive. Anthocyanins are associated with anti-inflammatory and antioxidant properties and are the primary reason that "eat a rainbow" nutritional advice specifically values red and purple vegetables. Red Baron consumed raw (where anthocyanins are most bioavailable) provides significantly more of these compounds than white or yellow onion varieties of equivalent size. The deeper the red colour in the flesh rings, the higher the anthocyanin concentration.
Sowing & Harvest Calendar
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| Exhibition sow (Jan-Feb indoor) |
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| Kitchen crop sow (Mar-Apr indoor) |
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| Plant out (Mar-May) |
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| Bulb development (May-Aug) |
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| Harvest and cure (Aug-Sep) |
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| In storage (Sep-Apr) |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Pale rings; weak red colour | Insufficient sun; waterlogged soil; excess nitrogen | Red Baron's colour is produced by light-responsive anthocyanin synthesis. Full sun is essential. Avoid waterlogged conditions or over-rich, high-nitrogen soil that produces leaf growth at the expense of bulb quality. Well-drained, moderately fertile ground produces the deepest ring colour. |
| Poor storage; rotting in store | Incompletely cured; thick necks before storing | Cure for at least 2 weeks until all necks are papaper-dry. Never store bulbs with soft or thick necks -- these are the primary entry points for storage rot. Check stored onions weekly and remove any showing soft spots or mould immediately. |
| Small bulbs | Insufficient season; sown too late; overcrowded | For maximum bulb size: sow in January-February. March-April sowing produces smaller bulbs. Thin to 10-15cm -- crowded plants produce small, spindly bulbs regardless of sowing date. |
| Tops not falling; won't ripen | Waterlogged; excess nitrogen; long-season effects | Stop watering once bulbs are visible at the soil surface. High nitrogen soil delays ripening. In very wet seasons, gently bend tops over to encourage drying if they haven't fallen naturally by mid-September. |
Vegetable Specifications
Deep crimson rings that store until spring -- the RHS-approved red onion worth growing over any other
Sow January-February indoor at 10-15°C for exhibition size, or March-April for an excellent kitchen crop. Plant pencil-thick seedlings at 10cm in rich well-drained soil. Stop watering when tops begin to fall. Cure for 2 weeks. Store in cool, airy conditions for up to 9 months -- year-round red onions with the beautiful concentric rings from a single summer sowing.
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