How to Grow Cosmos
'Double Click Rose Bon Bon' from Seed
The Cosmos that became a peony — fully double pompom blooms in rich vintage rose-pink, each up to 8cm across with layer upon layer of tightly ruffled petals; part of the award-winning Double Click series and the most volumetric, most luxurious cut flower in the Cosmos range
Standard Cosmos flowers are flat, open, simple daisies — eight broad petals around a central disc. 'Double Click Rose Bon Bon' is the opposite of this in almost every structural respect. The flowers are fully double — no visible central disc, no open space, just layer upon layer of ruffled petals packed tightly into a rounded pompom up to 8cm across. The effect is unmistakably peony-like: a dense, voluminous, richly textured flower head that the word "Cosmos" does not in any way prepare you for when you first see it in the garden. If you removed the fine, feathery Cosmos foliage and substituted it with bolder leaves, the flower head alone would pass as a small garden rose or miniature dahlia.
This is the Cosmos for the gardener who wants the volume and luxury of a peony-style bloom without the years of establishment that peonies require. 'Double Click Rose Bon Bon' achieves it from seed in one season — sow in March, pinch in April, plant out in June, and by July the double pompoms are appearing on tall, sturdy stems that last up to ten days in the vase. The rose-pink colour is a rich, warm vintage tone — not the cool, bright pink of modern garden varieties, but the slightly muted, deeply pigmented rose that the vintage and romantic garden aesthetic prizes above anything else.
Quick Facts at a Glance
Plant Type
Half-Hardy Annual (H2)
Flower form
Fully double pompom — 8cm across; looks like miniature peony
Colour
Rich vintage rose-pink — warm, deeply pigmented
Height
90–120cm — tall, sturdy cutting stems
Golden Rule
Poor soil, NO feeding — Cosmos starvation rule
Difficulty Rating
2 out of 5 — same ease as all Cosmos; starvation rule essential
Understanding the Flower
'Double Click Rose Bon Bon' is part of the Double Click series — a breeding programme focused specifically on producing fully double Cosmos bipinnatus flowers with the maximum number of ruffled petals. The series name reflects the double-petal structure; "Rose Bon Bon" identifies the specific rich rose-pink colour form within the series. The flowers are the most structurally complex of any Cosmos variety available from seed — the double pompom form represents a significant departure from the open single daisy that defines the species' natural flower.
The Pompom Form — What Makes It Different from All Other Cosmos
Standard Cosmos flowers are open, flat, and single — their beauty lies in translucency, simplicity, and lightness. 'Double Click Rose Bon Bon' is dense, rounded, and complex — its beauty lies in volume, texture, and depth. The layered ruffled petals create the same visual richness as a garden rose or peony, but on a Cosmos stem with the distinctive ferny foliage that no rose or peony can provide. In a mixed summer arrangement, a single pompom stem of 'Double Click Rose Bon Bon' provides the focal flower — the substantial, eye-catching element around which lighter, airier flowers (single Cosmos, Ammi, Nigella, cornflowers) arrange themselves naturally.
⚠️ The Starvation Rule — Essential, and Especially Important for Double Varieties
Do not feed 'Double Click Rose Bon Bon'. Do not plant in freshly manured ground. The starvation rule applies to all Cosmos but is particularly important for double-flowered varieties, which may have an even stronger tendency to produce lush foliage at the expense of flowers in rich conditions. Lean, poor, unfed soil in full sun produces the most abundant double pompom production.
Sowing & Growing On
Cut When Half-Open — Different from Single Cosmos Varieties
Single Cosmos are cut at bud stage — when petals are just beginning to separate. Double Cosmos should be cut when the flower is approximately half to fully open — because the dense pompom form does not open well once cut in the early bud stage. Allow the pompom to develop to roughly half-full before cutting. At this stage the flower will continue opening in the vase and provide 7–10 days of full display.
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Sow indoors March–April at 20°C, 5mm deep. Sow into individual modules or small pots. Keep at 20°C. Germination in 5–14 days. Grow on in bright, cool conditions after germination — cool greenhouse, bright windowsill. Do not allow seedlings to become too warm or leggy before outdoor planting time.
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Pinch the growing tip at 20cm — essential for all Cosmos. Remove the top 2–3cm above a leaf joint when plants are 20cm tall. This produces multiple side shoots and dramatically increases flower production. Unpinched double Cosmos plants are particularly disappointing — a single tall stem producing very few pompom heads. Pinching produces a bushy plant with many branching stems, each terminating in the characteristic double bloom.
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Plant out late May–June in full sun on lean, unfed soil. Space 45cm apart. Do not add compost, manure, or fertiliser to the planting area. The leanest, sunniest position in the garden is ideal. Water in well after planting, then largely leave alone — established Cosmos are surprisingly drought tolerant.
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Cut when pompoms are half to fully open — unlike single Cosmos varieties. At half-open stage, strip all lower foliage, condition in cool water for two to three hours, then arrange. Change water every two to three days. Vase life is 7–10 days for fully double varieties.
Growing On & Care
The Focal Flower
In a mixed cutting garden arrangement, 'Double Click Rose Bon Bon' functions as the focal flower — the substantial, volumetric element that draws the eye. A hand-tied bouquet of three double pompom stems surrounded by single Cosmos 'Purity', Ammi majus, and Nigella creates a complete, professionally styled arrangement with minimal effort. The pompom provides the richness; the lighter flowers provide the airy frame.
Wedding Floristry
The vintage rose-pink pompom is one of the most requested Cosmos flower forms for wedding work — it provides the peony-like volume that defines romantic, cottage garden wedding floristry without requiring peonies (which are expensive and have a very short season). 'Double Click Rose Bon Bon' at full peak is available continuously from July through November — a far longer and more reliable supply than actual peonies from a cutting garden.
Lower Seed Yield
Double-flowered Cosmos varieties typically produce fewer seeds per plant than single varieties, as the reproductive structures are replaced by extra petals. Collect seeds from the few flowers allowed to set seed at season's end — the seed heads will be smaller than single varieties but viable. Store dry in a paper envelope for next season.
Support May Be Needed
The heavier double pompom flower heads on tall (90–120cm) stems may require support in exposed or windy positions. Insert bamboo canes or twiggy pea-sticks when plants are 40–50cm tall. In a sheltered garden or when plants are grown close together in a row, mutual support is usually adequate. The ferny Cosmos foliage helps disperse wind pressure that might otherwise topple isolated specimens.
Pollinator Note
Double-flowered Cosmos varieties are less accessible to pollinators than single varieties — the dense petal layers reduce access to the central nectar and pollen. If pollinator support is a priority, combine 'Double Click Rose Bon Bon' with single-flowered Cosmos varieties like 'Purity' or 'Daydream' that provide the open, accessible disc for bees and butterflies.
The Feathery Foliage Contrast
One of the most striking visual qualities of 'Double Click Rose Bon Bon' in the garden is the contrast between the dense, structural double pompom flowers and the incredibly fine, feathery, thread-like Cosmos foliage. This contrast — heavy flower, light foliage — is what gives the plant its distinctive character and makes it more interesting than garden roses and dahlias, which match heavy flowers with proportionally substantial foliage.
When to Expect Flowers
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| 🌱 Sow indoors |
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| 🌿 Plant out |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Foliage only, no pompoms | Rich soil; any feeding; no pinching | Both the starvation rule (lean soil, no feeding) and pinching at 20cm are essential for productive double Cosmos. Rich soil produces foliage; no pinching produces a single-stemmed plant with very few flowers. Address both simultaneously for the best response. |
| Pompoms not fully double — some single flowers | Normal variation in double Cosmos from seed | A small proportion of double Cosmos seedlings may produce semi-double or even single flowers — this is normal genetic variation in seed-grown double varieties. Remove or deadhead these plants and allow the fully double ones to provide your cutting material. The fully double plants are easily identified by the dense, rounded pompom form as soon as flowering begins. |
| Pompoms flopping over on stems | Heavy double flower heads in exposed conditions | Support with bamboo canes or twiggy sticks installed at 40–50cm plant height. In a sheltered position, support is usually not needed. Planting in a block or row rather than as isolated specimens provides mutual support from the overlapping stems and foliage. |
| Short vase life | Cut too early (at very tight bud stage); foliage left in water | Unlike single Cosmos, double varieties should be cut when at least half-open. Strip all foliage below the waterline entirely. Change water every two to three days. Condition in cool water for two to three hours before arranging. |
Plant Specifications
The Cosmos that became a peony — fully double pompom blooms from a seed packet
'Double Click Rose Bon Bon' produces the most volumetric, most luxurious, most peony-like flower available from a Cosmos seed packet — a fully double pompom up to 8cm across with layer upon layer of rich vintage rose-pink ruffled petals, on long ferny-foliaged stems, continuously from July to November. Sow March in lean compost, pinch at 20cm, plant in the poorest sunny position, cut pompoms at half-open stage — and provide the most architecturally beautiful cut flower in the entire Cosmos range for the summer vase and the summer wedding table.
Shop Cosmos Double Click Rose Bon Bon Seeds →