How to Grow Calendula
'Wintersun' from Seed
The pot marigold that ignores winter — bred specifically for cold tolerance, flowering through autumn and into winter during mild spells when the rest of the garden is bare, a vital nectar source for bumblebees on warm January days, and the brightest thing in the garden from November through February
Every other calendula in this range is a summer annual — sow in spring or autumn, flower through summer and into autumn, finished by the frosts. 'Wintersun' is different at a fundamental level: it has been specifically bred for cold tolerance, rated H5 on the RHS hardiness scale (capable of withstanding temperatures to −15°C) compared with H3 for standard calendulas (frost-susceptible). This single difference opens up a use case that no other calendula can offer — growing through autumn and continuing into winter during mild spells, providing creamy-yellow and apricot flowers in November, December, January and February when the rest of the garden is bare and grey.
The human value of a flowering calendula in January is obvious to anyone who has experienced a British winter — the warm, golden tones against bare soil and dead stems are genuinely cheering in a way that photographs cannot convey. The ecological value is equally significant: bumblebee queens emerge from hibernation on unexpectedly warm winter days, sometimes as early as February or even January in a mild year, and they need nectar immediately to survive and build energy for colony establishment. A patch of Wintersun in flower during a January warm spell is one of the very few available nectar sources in the entire garden — and arguably the single most practically beneficial thing a gardener can plant for overwintering bumblebees.
Quick Facts at a Glance
Plant Type
Hardy Annual (H5 — exceptionally cold-hardy)
Sowing Time
Aug–Sep for winter · Mar–May for summer
Winter Flowering
Oct – Feb (mild spells)
Position
Full sun or partial shade; any soil
Height
30–45cm
Difficulty Rating
1 out of 5 — Very Easy
Understanding the Plant
'Wintersun' is Calendula officinalis — the same species as all pot marigolds — but bred through successive selection for cold tolerance and continued flowering in the low light and reduced temperatures of autumn and winter. The H5 hardiness rating indicates it can survive temperatures down to −15°C, significantly hardier than the H3 standard calendulas (frost-susceptible below approximately −5°C). In practice this means established Wintersun plants survive UK winters with normal frosts intact, continue to produce new growth during mild spells, and flower on every calm, bright day when temperatures rise above about 5°C — even in the depths of winter.
The flowers are large, semi-double, in shades of creamy-yellow and apricot — warmer and softer than a pure yellow but without the vivid orange of summer marigolds. This is a palette that works particularly well in the low winter light, where the warm, diffuse tones glow rather than blaring. The blooms face toward the sun (heliotropism) and will close on overcast days and at night in exactly the same way as summer calendulas — the closing flowers on a grey winter day can look almost more beautiful than the open ones on a sunny June afternoon.
H5 vs H3 — The Hardiness Difference That Matters
All other calendulas in this range are rated H3 — "tender in frost" — meaning they are damaged or killed by temperatures below approximately −5°C, and their season ends with the first autumn frosts. Wintersun's H5 rating means it survives temperatures down to −15°C and can persist through normal UK winters as an established plant. In the coldest periods (prolonged hard frost below −5°C) Wintersun may show some damage to flowers and growing tips, but it recovers in mild spells. In mild maritime climates (south and west coasts, urban areas), winter flowering can be almost continuous from October through to March.
The Pollinator Lifeline — January and February Nectar
Bumblebee queens emerge from hibernation during warm spells throughout winter — sometimes as early as January in mild years. On emergence, they are cold, weak, and critically short of energy. Without accessible nectar within flying distance of their hibernation site, a queen that emerges on a January warm day may starve before the weather allows her to fly further. Wintersun in flower during these warm spells — particularly in a sheltered, south-facing position — provides one of the very few available nectar sources during the most critical period of the bumblebee colony cycle. The practical impact of one patch of Wintersun on a local bumblebee population is genuinely significant.
Sowing for Winter Flowers
The Key Sowing Date for Winter Display
To flower in winter, Wintersun must be sown in August or September. Plants sown in this window establish through autumn, develop a compact root system, and are well-positioned to continue flowering through mild winter periods. Spring sowings (March–May) produce summer and autumn flowering plants of excellent quality, but they will not be established enough to continue through winter — they follow the standard summer calendar. For the winter display that makes Wintersun unique, sow in August.
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For winter flowers: sow direct in August–September at 1cm depth. Cover well — darkness is required for germination as with all calendulas. Germination takes 7–10 days. Thin to 30cm spacing once seedlings are established. These plants will flower in October and continue through mild winter spells into February or March.
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Choose a sheltered, south-facing position for winter. A south-facing wall, fence, or well-sheltered bed provides the additional warmth and protection from cold winds that allows Wintersun to perform at its best through winter. In exposed positions, frost severity is greater and the plants may experience more damage to flowers during cold spells.
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For summer flowers: sow direct March–May at 1cm depth. Produces a standard summer to autumn display from June to October. Less distinctive than the winter use but still an excellent, reliable calendula for the summer border.
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Deadhead when accessible. Remove spent heads during mild spells. In very cold winter periods, the plant may not be growing actively and deadheading is less critical than in summer — but regular removal of old heads during mild windows stimulates new bud production and keeps plants tidy through the winter months.
Growing On & Winter Care
Winter Behaviour
During the coldest periods (sustained frost below −5°C), Wintersun flowers may be damaged and the growing tips may darken and die back slightly. This is normal and not permanent — the plant recovers during mild spells, producing new buds from the base and lower side shoots. Do not cut back during cold periods — the damaged upper growth provides some frost protection to the lower, healthy growth below.
Light Requirements
Full sun or partial shade — Wintersun is unusually flexible for a calendula, tolerating partial shade better than standard summer varieties. In winter when sun is low and scarce, partial shade is acceptable. In the bleakest periods, even under an overcast sky, established plants continue to develop buds that open on the next sunny day.
Winter Bee Value
Position Wintersun in a sheltered spot accessible to flying insects — not under a dense canopy or in a north-facing pocket where bumblebees are unlikely to venture in cool conditions. A sunny south-facing spot against a wall or fence is ideal: the warmth absorbed by the wall creates a microclimate where temperatures can be several degrees higher than in the open garden, and bumblebee queens are most likely to emerge and forage here on warm winter days.
Soil Flexibility
Wintersun is more tolerant of a wider range of soil conditions than standard summer calendulas — average to moist soil works well for winter growing, where the lean-soil preference of summer varieties is less important. Avoid waterlogged conditions, which rot the crown during cold winter periods. Well-drained soil in a sheltered position gives the best results through winter.
Companions for Winter Display
Wintersun's creamy-yellow and apricot tones work beautifully with other winter-flowering and early-spring plants. Wallflowers in orange and red tones provide warm harmony; forget-me-nots in blue create a classic complementary contrast. Winter pansies and violas in purple or wine-red provide a low, close-planted foil. Together these create a winter and early spring border of genuinely sustained colour through the most difficult months.
Edible Winter Flowers
The creamy-apricot petals are fully edible in winter as in summer. A mid-January bowl of soup garnished with fresh calendula petals is genuinely unusual and genuinely beautiful — and the contrast between the cheerful golden flower and the grey midwinter context makes it somehow more remarkable than the same garnish in July.
Flowering Calendar — Summer & Winter Display
Wintersun has two distinct use cases with different sowing windows. The winter display — the unique capability of this variety — requires an August or September sowing. The summer display follows the standard calendula calendar from a spring sowing. Both are described below.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
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| 🍂 Sow for winter |
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| 🌿 Sow for summer |
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| ☀️ Summer flower |
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| ❄️ Winter flower |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| No winter flowers after August sowing | Exposed position; very severe winter; spring sowing used instead | Ensure the August/September sowing window is used — a spring sowing will not establish sufficiently to survive and flower over winter. Position in a sheltered, south-facing spot. In the coldest UK winters (prolonged frost below −10°C), even Wintersun may not flower between December and February, resuming in March as temperatures rise. |
| Crown rot in winter | Waterlogged soil during cold wet weather | Ensure adequate drainage. Wintersun can withstand cold but not cold combined with waterlogging. On heavy clay, raise the bed or improve drainage before planting. A layer of grit around the crown helps prevent rotting in winter wet. |
| Flowers damaged by frost | Normal in hard frosts | Frost-damaged flowers on Wintersun are a normal part of winter growing — the plant recovers when temperatures rise. If a prolonged hard frost is forecast, a single layer of garden fleece overnight provides significant protection. Remove fleece as soon as the frost passes to allow air circulation and avoid mildew. |
Plant Specifications
The pot marigold that gives when the garden has nothing left to give
'Wintersun' occupies a unique position in the seed range: it is the only plant that flowers reliably through the British winter, providing creamy-gold colour during the bleakest months and nectar for bumblebees during the critical late-January to March window when no other nectar source is available. Sow in August, position in a sheltered south-facing spot, and let it do the one thing no other calendula can do — bring the warmth of the summer sun into the depths of a British January.
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