How to Grow Cleome
'Cherry Queen' (Spider Flower) from Seed
The Spider Flower — vivid carmine-rose spherical flower heads topped with extraordinarily long curling stamens that extend outward like spider legs or a freeze-framed firework, a 1.2m tropical South American annual that thrives in British heat, releases evening scent, and is adored by bees and moths alike
If a border feels flat in August — when the spring flurry has passed and the autumn chrysanthemums have not yet arrived — Cleome is the solution. Standing at 1.2m tall with large, spherical flower heads in vivid carmine-rose, each bloom extended and adorned by incredibly long, curling stamens that radiate outward like the legs of a spider or the explosion of a firework caught at its apex, 'Cherry Queen' provides a scale, exoticism, and vertical drama that very few annuals even attempt. It is a genuinely theatrical plant — impossible to ignore, instantly striking from across a garden, and capable of bringing a mid-border position to life from July to the first frosts.
The common name "Spider Flower" comes entirely from those stamens — the pollen-bearing filaments that extend up to 10cm beyond the petals in a spiralling cluster that genuinely resembles a spider at rest. This structure is not ornamental coincidence but a pollination strategy: the long stamens ensure that any insect visiting the flower becomes thoroughly dusted with pollen before departing. In the evening, a sweet fragrance is released that attracts moths — Cleome is one of the very few flowering annuals that provides a meaningful evening nectar source for British moth populations.
Quick Facts at a Glance
Plant Type
Half-Hardy Annual — needs heat; frost-tender
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Sow Indoors
February–April at 20–25°C
Plant out
Late May–June (after all frost)
Height
Up to 1.2m — back of border
Difficulty Rating
3 out of 5 — needs heat and a long season
Understanding the Plant
Cleome hassleriana (formerly C. spinosa) is a half-hardy annual native to South America — Argentina, Paraguay, and Uruguay. In its native range it grows in open, sunny, disturbed ground and scrubland, and its preference for heat, drought tolerance, and frost sensitivity all reflect this tropical origin. In the UK it must be started early indoors and kept protected from frost until June — but once established in a warm, sunny border, it thrives through the British summer and flowers prolifically from July to the first hard frost.
The Spider Flower Mechanism
The long, curling stamens that give Cleome its common name are not merely decorative — they are the primary pollen-delivery mechanism. As a bee or bumblebee enters the flower seeking nectar, it must navigate past the extended stamens, which brush pollen onto the insect's body. The length of the stamens ensures that pollen is placed on the thorax and abdomen (rather than the leg baskets where it would be groomed off), increasing the probability that cross-pollination occurs at the next flower visited. The spider leg appearance is a byproduct of this very effective pollination strategy.
⚠️ Spiny Stems — Wear Gloves When Handling
Cleome stems have small but effective spines at the base of each leaf, similar in structure to rose thorns. These are not dangerous but can scratch bare skin during deadheading, cutting, or tying in. Wear gardening gloves when handling Cleome at any stem contact point. The flowers themselves are completely smooth and safe to handle bare-handed. The spines also make Cleome deer and rabbit resistant — a practical side benefit in gardens with browsing pressure.
Sowing & Establishment
Surface Sow — Light Required for Germination
Cleome seeds need light to germinate — surface sow onto moist compost and press gently into contact without covering. Covering with compost prevents germination. Keep at 20–25°C. Germination is erratic with Cleome — some seeds germinate in 10 days, others may take 30 days. This is normal for the species — do not discard the tray after 14 days. Continue to keep the surface moist and germination will continue for up to four weeks.
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Sow indoors February to April at 20–25°C. Surface sow onto moist seed compost in a propagator or on a warm windowsill at 20–25°C. Do not cover. Press seeds into good contact with the compost surface. Erratic germination 14–30 days is normal. A heated propagator produces the most consistent germination.
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Pinch the growing tip when seedlings are 10–12cm. This is the single most important management step for Cleome: pinching out the very tip of the main stem when plants are 10–12cm tall encourages branching and produces a bushy plant with multiple flower heads rather than one central spike. A pinched Cleome produces three to five times more flowers than an unpinched one.
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Pot on as plants grow — they grow fast. Cleome is a vigorous, fast-growing plant that will outgrow a seed module or small pot quickly. Pot on to 7cm, then to 12cm, then to a 2-litre pot if needed before the planting-out date. Each pot-on keeps the plant in active growth.
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Plant out late May to June — only after all frost risk has passed. Cleome is frost-tender — even a light frost kills young plants. Do not plant out before late May in most UK locations. Choose the warmest, most sheltered, sunniest position available. Plant 50–60cm apart at the back of the border to accommodate the eventual 1.2m height.
Growing On & Care
Full Sun, Sheltered
Cleome demands full sun and shelter from strong winds. The tall flower heads are vulnerable to wind damage — stake with bamboo canes in exposed positions when stems reach 60cm. In full sun and shelter, Cleome becomes a robust, drought-tolerant plant of impressive presence. In shade or wind, it becomes drawn, unstable, and reluctant to flower.
Evening Scent and Moths
The evening fragrance of Cleome is distinctive and pleasant — a sweet, slightly spicy scent released as temperatures drop in the evening. Position near a seating area or open window to appreciate this quality. The fragrance is the primary attraction for moths, which visit the flowers through the evening and night. Cleome is one of very few UK garden annuals with genuine moth pollinator value.
Self-Seeding
Cleome self-seeds very freely — the long seed pods that develop after flowering contain large quantities of seed that scatter around the base of plants. In subsequent years, self-seeded Cleome emerges in the border and can produce surprising amounts of new plants without any intervention. Remove unwanted seedlings early as they establish quickly.
Drought Tolerant Once Established
Once established with a good root system (six to eight weeks after planting out), Cleome is surprisingly drought tolerant — reflecting its South American scrubland origin. Water young transplants regularly for the first month; established plants need only supplementary watering in very extended dry spells. In typical UK summer conditions, established Cleome thrives without regular watering.
The "Bare Legs" Problem
Cleome's lower stems tend to become bare and somewhat scruffy-looking as the season progresses — the lower leaves yellow and fall while the upper stems continue producing flower heads. This is a known characteristic of the species rather than a problem. Manage it by planting something bushy and dense (Cosmos, Nicotiana, or Salvia) in front of the Cleome at 40–50cm height to conceal the lower stems while the flower heads remain visible above.
Bee and Moth Magnet
The RHS Plants for Pollinators designation reflects Cleome's outstanding ecological value. Bumblebees and honeybees visit the flowers continuously through the day; moths from several species visit from dusk onwards. In an ecology-focused garden, Cleome provides sustained dual-shift pollinator support that most plants cannot offer.
When to Expect Flowers
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
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| 🌱 Sow indoors |
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| 🌿 Plant out |
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| 🌸 Flowers |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Poor or erratic germination | Seeds covered; temperature too low; old seed | Surface sow only — covering prevents germination. Maintain 20–25°C throughout the germination period; below 18°C germination is very unreliable. Germination is naturally erratic with Cleome — wait up to 30 days before considering the tray a failure. Use fresh seed each season. |
| Few flowers, single-stemmed plant | Growing tip not pinched | Pinch the growing tip when plants are 10–12cm tall — this is essential for Cleome. Unpinched plants produce one main flower head and very few side branches. Pinched plants produce four to six or more flowering stems, dramatically increasing output. |
| Plants stunted or fail after planting out | Planted too early; frost damage | Wait until late May or June in most UK locations — no Cleome outside before all frost risk has passed. Even a single light frost kills young plants entirely. If caught by an unexpected late frost, protect with fleece or cloche overnight. |
| Bare, scruffy lower stems | Normal characteristic of the species | This is a species habit, not a problem to solve. Plan for it by planting a bushy companion (Cosmos, Nicotiana) in front at planting time. The lower bare stems are invisible once the companion is established and the Cleome flower heads tower above both plants. |
Plant Specifications
The Spider Flower that brings the tropical border to any British summer
'Cherry Queen' is the plant for the moment in midsummer when the border needs drama — something tall, something striking, something genuinely unlike anything else flowering at the same time. Start early, pinch promptly, plant in the warmest available position, and let the 1.2m spider flower heads with their extraordinary trailing stamens do what they were evolved to do: stop people in their tracks and draw bees and moths from across the garden.
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