How to Grow Dahlia
'Yankee Doodle Dandy Mix' from Seed
The two-tone dahlia with a collar — a Collerette type producing large 7cm flowers in pink, white, yellow, and mauve, each with a distinctive inner ring of shorter petals in a contrasting colour that frames the open centre; compact and bushy at 50–60cm, with no staking needed, and open flowers that make it one of the most valuable dahlias for bees and butterflies in the border
Among the many different dahlia flower forms, the Collerette is one of the most easily recognised and one of the most botanically interesting. A standard single dahlia has one ring of outer petals (ray florets) surrounding a central disc. A collerette dahlia has the same outer ring of long petals — but between those outer petals and the central disc, there is a second, inner ring of much shorter petals called the "collar," which is typically a different colour or shade from the outer petals. This collar creates a two-tone, layered appearance that makes the flower look simultaneously simple and complex — a familiar form made newly interesting by the inner ring.
'Yankee Doodle Dandy' produces these collerette flowers in a mix that includes pinks, whites, yellows, and mauves, each with its distinctive contrasting collar. The plants are compact and bushy at 50–60cm — no staking required — and the open centres of the flowers (both the collar and the central disc are accessible to insects) make this one of the most pollinator-friendly dahlia types available. The RHS Plants for Pollinators designation reflects what is visible in any garden where it grows: a continuous presence of bees and butterflies throughout the flowering season.
Quick Facts at a Glance
Plant Type
Half-Hardy Perennial H2, grown as annual
Flower type
Collerette — outer petals + distinctive inner collar ring in contrasting colour
Flower size
Up to 7cm across; open centre visible
Colours
Pink · white · yellow · mauve — bicolour two-tone combinations
Height
50–60cm — compact; no staking needed; ideal for containers
Difficulty
2 out of 5 — straightforward; same as all dahlias
Understanding the Collerette Form
In formal dahlia classification, a Collerette is defined by three structural elements: an outer ring of flat, overlapping ray petals; an inner ring of shorter petals (the collar) that typically curl slightly inward or outward; and an open, visible central disc of stamens and pistils. The collar is the defining element — it is botanically a second row of ray petals that have been modified in length and, typically, colour, creating the two-layer, two-tone effect. The open disc at the centre means both bees (which can reach the pollen directly) and butterflies (which can reach the nectar) benefit from the flower in a way that densely packed pompon, ball, or decorative dahlias cannot provide.
Why the Collar Makes This Dahlia Different
Most double and semi-double dahlias are designed (through breeding selection) to produce as much petal material as possible — progressively replacing the central disc with additional petals until the centre is hidden or eliminated entirely. The collerette deliberately retains the open centre and adds the collar as an ornamental element without eliminating access for pollinators. The result is a flower that is simultaneously more complex and more intricate than a simple single, while remaining fully accessible to insects. For gardeners who want beautiful, interesting dahlias that also genuinely support biodiversity, the collerette form offers this combination more reliably than any other dahlia type.
The Two-Tone Colour Effect
Each 'Yankee Doodle Dandy' flower displays at least two colours — the outer petals and the collar are typically different shades or tones from each other. A pink outer ring with a white collar; a mauve outer with a pink collar; a yellow outer with a pale yellow or white collar. This built-in bicolour quality gives the mix a visual richness that solid-coloured dahlias cannot match — each individual flower is more interesting close up than it appears from a distance, which rewards closer observation and makes them particularly engaging as container plants near a seating area.
Sowing & Growing On
The Same Method as All Dahlias — Warmth, Pinching, and Deadheading
'Yankee Doodle Dandy' follows exactly the same growing method as all dahlia varieties: warm indoor start, pinch at 3–4 pairs of leaves, plant after frost, feed from first bud, deadhead consistently. The compact 50–60cm habit means no staking is needed in most positions, and the open flower form means pollinators arrive without any further encouragement.
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Sow indoors February–April, 0.5cm deep, at 18–20°C. Into seed trays or small individual pots. Cover with 5mm of compost. Keep at 18–20°C throughout germination. Move to bright, cooler conditions (15°C) immediately after germination — warm conditions with low light produce leggy seedlings. Germination in 7–14 days.
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Pot on into individual 9cm pots when 2–3 true leaves appear. Handle seedlings by the seed leaves to avoid bruising the stem. Grow on in a bright position at 15–18°C. Keep moist but never waterlogged — dahlia seedlings are susceptible to damping off in overly wet conditions.
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Pinch out growing tip at 3–4 pairs of leaves. Remove the top shoot above the third or fourth leaf pair. This one action converts a single-stemmed plant with a few flower buds into a multi-branched, bushy plant that carries many more flowers from July through October. The pinched plant recovers and begins branching within 7–10 days.
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Harden off and plant out late May–June after all frost, in full sun. Place pots outside in a sheltered position during warm days and bring in at night for 7–10 days before permanent planting. Plant in rich, fertile, well-drained soil in full sun. Space 40–50cm apart (or one per large container of at least 30cm diameter).
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Feed weekly with high-potash fertiliser from first bud; deadhead every spent flower. Liquid tomato feed once a week from the moment the first buds appear. Deadhead every flower as soon as the petals begin to drop — this prevents seed setting and maintains continuous flower production until the first autumn frost.
Growing On & Care
The Best Dahlia for Pollinators
The open-centred collerette form provides the most accessible dahlia flower for pollinators. Both the collar and the central disc offer nectar and pollen to bees, butterflies, and hoverflies — and the flower's structure guides visitors efficiently to the reward. From mid-July to October, 'Yankee Doodle Dandy' flowers are among the most consistently visited late-season flowers in the border, providing valuable nectar support through the long period after most summer flowers have finished.
Container and Patio Use
At 50–60cm with a compact, bushy habit that needs no staking, 'Yankee Doodle Dandy' is one of the most suitable dahlias for container growing. Minimum 30cm diameter container with drainage. Fill with rich, fertile compost. Water every day or two in warm weather — containers dry faster than open ground. Feed with liquid tomato feed every 7–10 days from first buds. Position in the warmest, sunniest spot available — dahlias in containers perform best with maximum sun exposure.
As a Cut Flower
The collerette form makes an attractive and distinctive cut flower — the two-tone collar adds a complexity that single and semi-double flowers lack. Condition immediately after cutting: dip the bottom 2cm of stem in boiling water for 10 seconds, then plunge into deep cold water. Vase life is 5–8 days with this treatment. Cut when the outer petals are fully open and the collar is developed but the central disc is not yet fully open.
Colour Combinations
The pink, white, yellow, and mauve tones of 'Yankee Doodle Dandy' work beautifully in a soft, romantic planting scheme alongside Cosmos in white and pink, Verbena bonariensis (purple, airy), and Salvia 'Victoria Blue'. The compact 50–60cm height places it perfectly at the mid-border layer — in front of taller grasses or perennials but behind lower-growing annuals. In a container, one plant of 'Yankee Doodle Dandy' alongside trailing Verbena or Bacopa creates an attractive, long-lasting display.
Tubers and Winter Storage
Like all dahlias, 'Yankee Doodle Dandy' forms tubers underground through the growing season. After the first frost blackens the foliage, cut stems to 10cm and fork up the small tubers carefully. Allow to dry for a week then store in dry compost or coir in a frost-free location. Label by flower colour — a pink and a yellow plant produce identical-looking tubers. Second-year tuber plants are larger and more floriferous than first-year seed plants.
No Staking Needed
The compact, bushy habit of 'Yankee Doodle Dandy' at 50–60cm means that in most UK garden positions, staking is not required. The pinched, branching framework of the plant is naturally self-supporting, and the flower heads (7cm) are small enough not to create excessive wind resistance or top-heaviness. In very exposed coastal positions or gardens prone to strong winds, a single central cane per plant provides sufficient support.
Sowing & Flowering Calendar
| 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 |
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| Flowers not showing collar | Normal early-season variation; bud too young | The collar develops fully as the flower opens. In early buds it is compressed and may not be visible. Wait for the flower to open fully — the collar emerges as the outer petals flatten out and the inner ring of shorter petals extends. Occasionally seed-raised plants produce flowers with a less-defined collar — this is normal variation. |
| Slugs and snails attacking young plants | Young growth highly attractive to slugs | Protect immediately after planting out with a copper tape collar around the base, a physical barrier, or regular hand-picking after dark. Young dahlia growth is one of the most slug-attractive plants in the summer garden — the first two or three weeks after planting are the most vulnerable period. Once established, the plants are less vulnerable. |
| Flowering slowing in late summer | Deadheading insufficient; seed setting | Inspect every plant every two to three days and remove every spent flower without exception. Even a few seed heads forming signals the plant to reduce flower production. Consistent deadheading is the single most important ongoing management practice for all dahlias from July through October. |
| Leaves yellowing or mottled | Dahlia mosaic virus or aphid damage | Aphids (often visible on the underside of leaves and on buds) spread dahlia mosaic virus. Control aphid populations promptly with strong water jets or insecticidal soap. Remove any severely virus-affected plants to prevent spread. Do not save tubers from mottled or distorted plants. |
Plant Specifications
The two-tone collar dahlia — complex, beautiful, and one of the most valuable flowers in the border for bees
Sow February–April at 18–20°C. Pinch at 3–4 pairs of leaves. Plant in full sun after frost. Feed weekly from bud. Deadhead every spent flower. From July to October, 'Yankee Doodle Dandy' produces a continuous display of two-tone collerette flowers in pink, white, yellow, and mauve — each with its distinctive contrasting collar — on compact, self-supporting 50–60cm plants that suit containers as well as borders, and provide open, accessible flowers for bees and butterflies throughout the late-summer garden.
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