Plant Library
Types of dahlias: 10 flower forms from pompon to dinnerplate
The 10 dahlia flower forms per the American Dahlia Society — single, anemone, collerette, waterlily, decorative, ball, pompon, cactus, semi-cactus, stellar
Types of dahlias: 10 flower forms from pompon to dinnerplate
Dahlias deliver more flower power per square foot than almost any other summer perennial — a single mature plant can produce 30 to 50 blooms from July through frost. The catch: with 57,000+ named cultivars and at least 10 distinct flower forms, choosing the right dahlia for your border (or your vase, or your competition show) can feel impossible without a classification map. This guide walks through the 10 official flower forms recognised by the American Dahlia Society (ADS), with sizes from miniature to giant dinnerplate, named cultivars in each group, overwintering rules, and the pet-safety note every dog and cat owner needs. The ASPCA confirms dahlias are toxic to dogs and cats — symptoms are usually mild GI upset.
Match a dahlia to your bed: Photograph your border in Growli and we measure light, soil drainage cues, and existing plants — then rank the dahlia forms and sizes most likely to perform where you live.
How the 10 forms are classified
The American Dahlia Society assigns each registered dahlia a 4-digit classification number combining size, form, and colour. The first two digits are the size code, the third is the form code, and the fourth is the colour code.
Size codes range from AA (giant, 10 inches and larger — the "dinnerplate" dahlias) down through A (large, 8 to 10 inches), B (medium, 6 to 8 inches), BB (small, 4 to 6 inches), M (miniature, under 4 inches), and BA (ball/pompon variants).
Form is the shape and arrangement of the petals (called ray florets botanically) — the 10 main forms covered below.
Colour uses a single-digit code (white, yellow, orange, pink, red, lavender, dark red, dark pink, variegated, bicolor, blends).
The 10 dahlia flower forms
1. Single dahlias — Dahlia (FD code: SC)
The simplest dahlia form. A single row of 8 to 10 flat or slightly cupped ray florets arranged around a central disc of yellow stamens. Ray florets overlap uniformly in the same direction. Open and accessible to bees and butterflies — single dahlias are the most pollinator-friendly form. 'Mignon Single' series and 'Bishop of Llandaff' (single red with dark bronze foliage) are the most-planted singles.
Form: Single row of flat ray florets around exposed disc. Size range: Mostly B to M. Bloom time: July to frost. Use: Pollinator borders, naturalistic plantings.
2. Anemone dahlias — Dahlia (FD code: AN)
A central mass of dense tubular petaloids ringed by one or more rings of flat ray florets. Often the two petal types are contrasting colours, and the flower lacks a central disc. 'Totally Tangerine' (peach with golden cushion centre) and 'Brio' (red and yellow) are popular anemones.
Form: Outer ring of flat petals + central mass of tubular petaloids. Size range: B to BB. Bloom time: July to frost. Use: Borders, cut flowers.
3. Collerette dahlias — Dahlia (FD code: CO)
A single row of flat ray florets like a single dahlia, plus an inner ring of shorter petaloids (the "collar") around a central disc. The collar petaloids are approximately one-half to two-thirds the length of the ray florets and often a contrasting colour. 'Night Butterfly' (deep maroon with white collar) and 'Christmas Carol' (red with yellow collar) are classic collerettes.
Form: Outer ray florets + inner short collar + central disc. Size range: B to BB. Bloom time: July to frost. Use: Borders, cut flowers.
4. Waterlily dahlias — Dahlia (FD code: WL)
Flat-faced double flowers with broad slightly curved ray florets that resemble the shape of a waterlily blossom. Fully double — no visible disc or stamens. 'Cafe au Lait' (cream with hints of peach and pink — the most-photographed wedding dahlia in the world) and 'Gerrie Hoek' (pure pink) are the bestselling waterlilies.
Form: Flat double with broad slightly curved petals. Size range: B to A. Bloom time: July to frost. Use: Cut flowers, weddings, borders.
5. Decorative dahlias — Dahlia (FD code: D)
The largest group. Fully double flowers with broad flat petals that may be partially revolute (rolled backward) or partially involute (rolled inward). Petals are not heavily quilled like cactus types. Includes most of the giant "dinnerplate" dahlias. 'Thomas Edison' (deep purple, AA-class dinnerplate), 'Kelvin Floodlight' (yellow giant), and 'Penhill Watermelon' (10-inch coral and lavender) are showstopping decoratives.
Form: Fully double with broad flat petals. Size range: AA giant to M miniature. Bloom time: July to frost. Use: Borders, cut flowers, competition.
6. Ball dahlias — Dahlia (FD code: BA)
Globe-shaped fully double blooms with uniform ray florets that are involute (rolled inward) for most of their length and fully involute for more than half. Petal tips are circular and blunt with no point or notch. Tighter and more spherical than pompon dahlias and slightly larger. 'Cornel' (deep red ball, ADS Hall of Fame), 'Jowey Winnie' (lavender-pink), and 'Sylvia' (peach-orange) are bestselling balls.
Form: Globe-shaped with involute petals. Size range: 3.5 to 5 inches. Bloom time: July to frost. Use: Cut flowers, formal arrangements, competition.
7. Pompon dahlias — Dahlia (FD code: P)
Miniature globe-shaped double flowers with inward-curving petals, blunt or rounded at the tips. Stricter ADS definition than balls — pompons must be under 2 inches in diameter, perfectly spherical, and with petals fully involute their entire length. 'Bantling' (orange), 'Bonne Esperance' (pink), and 'Whale's Rhonda' (deep purple) are reliable pompons.
Form: Spherical with fully involute petals, under 2 inches. Size range: Miniature only. Bloom time: July to frost. Use: Cut flowers, competition, container plantings.
8. Cactus dahlias — Dahlia (FD code: C)
Spiky double flowers with fully revolute (rolled backwards) narrow pointed petals. When fully revolute, the edges of the petals roll so completely that the edges touch. Looks like a starburst or sea-anemone explosion. 'Park Princess' (pink), 'Nuit d'Ete' (deep maroon), and 'Kennemerland' (yellow) are popular cactus dahlias.
Form: Double with fully revolute narrow pointed petals. Size range: AA giant to BB. Bloom time: July to frost. Use: Borders, cut flowers, dramatic accents.
9. Semi-cactus dahlias — Dahlia (FD code: SC)
Between decorative and cactus. Pointed petals that are revolute for less than one-half their length. Slightly less spiky than cactus dahlias but still showing the pointed petal silhouette. 'Hy Suntan' (orange-bronze), 'Mick's Peppermint' (white striped with pink), and 'Karma Sangria' (peach-orange) are bestselling semi-cactus dahlias.
Form: Pointed double petals revolute less than half their length. Size range: AA to BB. Bloom time: July to frost. Use: Borders, cut flowers, competition.
10. Stellar dahlias — Dahlia (FD code: ST)
A newer form recognised by ADS in the 1990s. Fully double with slightly involute pointed ray florets that overlap to form a star-like silhouette — somewhere between a waterlily and a semi-cactus. 'Alloway Candy' (pink and white bicolor) and 'Tahiti Sunrise' (peach with darker centre) are popular stellars.
Form: Fully double with slightly involute pointed ray florets in a star pattern. Size range: B to BB. Bloom time: July to frost. Use: Borders, cut flowers.
Size — from miniature to dinnerplate
Across the 10 forms, dahlia size codes apply:
- AA / Giant ("Dinnerplate"): 10 inches or more across. Mostly Decoratives and Cactus types. 'Cafe au Lait' (waterlily-decorative borderline), 'Kelvin Floodlight', 'Thomas Edison', 'Penhill Watermelon'.
- A / Large: 8 to 10 inches across. 'Senior's Hope', 'Rip City'.
- B / Medium: 6 to 8 inches across. The size range used for most cut-flower production.
- BB / Small: 4 to 6 inches across. The "florist's dahlia" size for compact arrangements.
- M / Miniature: Under 4 inches across.
- Ball: 3.5 to 5 inches across (Ball form only).
- Pompon: Under 2 inches across (Pompon form only).
Plant height ranges from 18 inches (miniatures and edging dahlias) to 6+ feet for some giant dinnerplate cultivars. Tall cultivars need staking from planting time — never try to stake a mature dahlia, you will damage the stem.
PET SAFETY — dahlias are toxic to dogs and cats (ASPCA)
The ASPCA toxic plants database lists Dahlia spp. as toxic to dogs and cats. The toxic principle is unknown — ASPCA records mild gastrointestinal signs and mild dermatitis but does not identify the specific compound responsible.
Clinical signs after ingestion are usually mild: drooling, a sensitive tongue and gums, vomiting, and sometimes diarrhea. The ASPCA classification is "mild to moderate" — symptoms typically clear up within 24 hours and dahlia poisoning is not usually life-threatening.
All parts of the plant are technically toxic — leaves, stems, flowers, and tubers. Dogs that dig up freshly planted tubers and chew them are the most common emergency-vet calls in this category. Cats are at lower risk because they rarely chew dahlia foliage, but cut flowers brought indoors can attract cats with grass-chewing habits.
If a pet ingests any part of a dahlia, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435. Most cases involve mild GI upset that resolves in 24 hours without treatment, but call for guidance if symptoms persist or the dog is small.
If you have a dog that digs in beds, plant dahlia tubers in raised beds or behind low fencing for the first weeks — disturbed soil over a freshly planted tuber is the most attractive to digging dogs.
How to choose the right type of dahlia
Pick by use.
- Cut flowers and bouquets: Waterlily, Decorative B-class, Ball, and Pompon forms. 'Cafe au Lait', 'Linda's Baby', 'Sylvia', 'Cornel'.
- Wedding work: Waterlily 'Cafe au Lait' is the most-photographed wedding dahlia in the world. Ball-form 'Jowey Winnie' is the runner-up.
- Pollinator garden: Single and Collerette dahlias have accessible stamens — bees and butterflies forage them readily. 'Bishop of Llandaff' is the classic.
- Border drama: AA-class Decoratives and Cactus dahlias. 'Thomas Edison', 'Penhill Watermelon', 'Park Princess'.
- Containers and edging: Miniatures and Pompons. 'Mignon' series, 'Bantling'.
- Competition showing: Ball, Pompon, formal Decoratives. Check ADS classification before entering.
Pick by height and staking effort. Giant dinnerplate cultivars reach 4 to 6 feet tall and need stakes installed at planting. Edging miniatures stay 18 to 24 inches and need no support. Mid-height cultivars (3 to 4 feet) benefit from a single stake or grow-through ring.
Pick by climate. Most cultivars work across USDA zones 7 to 10 outdoors, with tubers lifted and stored in zones 7 and colder. UK gardens grow dahlias spectacularly — the cool damp summer suits them — but most regions need to lift and overwinter tubers.
Planting timing and overwintering by USDA zone
Spring planting (all zones with frost risk):
- Indoors: Start tubers in pots indoors 4 to 6 weeks before your last frost date — early March in zone 6, late March in zone 5. Pot up in 1-gallon containers, water sparingly until shoots emerge.
- Outdoors: Plant tubers directly outdoors after all frost danger and soil reaches 60°F — typically mid-May in zone 6, late May in zone 5, early April in zone 8.
Planting depth and spacing: Lay tubers horizontally 4 to 6 inches deep, with the "eye" (growing point) pointing up. Space 18 to 24 inches apart for smaller cultivars and 24 to 36 inches for giant dinnerplate types.
Overwintering by zone:
- USDA zones 8 and warmer: Tubers can stay in the ground. Cut back stems after first frost, mulch heavily with 4 to 6 inches of bark or chopped leaves. This covers most of the UK — gardens south of Manchester typically overwinter dahlias in the ground.
- USDA zones 7 and colder (most of the US Midwest, US Northeast, northern UK, Scotland): Lift and store tubers. Wait until first hard frost blackens the foliage. Cut stems back to 4 inches, lift the tuber clump with a fork (don't pull by the stem), let dry upside down in a frost-free shed for 1 to 2 weeks, brush off soil, and store in dry sand or vermiculite in a frost-free location at 40 to 50°F.
- Mild English winters (south-west England, Cornwall, urban London): Most gardeners successfully mulch in place rather than lift, especially on free-draining or sandy soils. Heavy clay still needs lifting because cold + wet rots tubers faster than cold alone.
Common care across the category
Plant in full sun — dahlias need 6 to 8 hours of direct sun for best flower production. Less sun gives weaker stems and fewer blooms.
Stake tall cultivars at planting. Insert a 5 to 6 foot stake when you place the tuber so the roots grow around it. Trying to stake a mature dahlia damages the brittle stem and tuber.
Pinch the central shoot when the plant is 12 to 18 inches tall — cut just above the third or fourth pair of leaves. This forces side branching and produces more (smaller) flowers and shorter, sturdier stems.
Disbud for size or leave alone for quantity. For competition-size blooms on Decoratives and Cactus types, remove the two side buds from each flower cluster so the plant puts all its energy into the central bud. For maximum bloom count, leave all three buds — you'll get three smaller flowers instead of one giant.
Deadhead aggressively. A dahlia that sets seed stops blooming. Cut spent flowers back to a leaf joint with a stem to encourage new flower production.
Feed weekly during bloom. Liquid tomato fertilizer (high in potassium and phosphorus) once a week from bud-set through frost keeps flower production going.
Water deeply at the roots — overhead watering on flowers causes botrytis (grey mould). A drip system or careful base watering is ideal.
Try Growli: Snap a photo of any dahlia with Growli — instant form ID and care plan in 60 seconds.
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Reviewed and updated by the Growli editorial team. For questions about anything here, open Growli and ask — or email hello@getgrowli.app.
Frequently asked questions
What are the main types of dahlias?
The American Dahlia Society classifies dahlias into 10 main flower forms: Single, Anemone, Collerette, Waterlily, Decorative, Ball, Pompon, Cactus, Semi-cactus, and Stellar. Sizes range from miniature (under 4 inches) to giant 'dinnerplate' (10 inches or more). The classification system assigns each registered dahlia a 4-digit code for size, form, and colour.
Are dahlias toxic to dogs and cats?
Yes. The ASPCA confirms dahlias are toxic to dogs and cats. The toxic principle is unknown — ASPCA records mild gastrointestinal signs and mild dermatitis. Symptoms include drooling, sensitive tongue and gums, vomiting, and sometimes diarrhea. All parts of the plant including tubers are technically toxic. Severity is mild to moderate — symptoms usually clear in 24 hours. Call ASPCA Animal Poison Control at (888) 426-4435 if a pet ingests significant amounts.
What is a dinnerplate dahlia?
'Dinnerplate' is the common name for AA-class giant dahlias — flowers 10 inches in diameter or larger. Most dinnerplate dahlias are Decorative form (broad flat petals), with some Cactus and Semi-cactus types reaching giant size. Classic dinnerplate cultivars include 'Cafe au Lait' (cream waterlily-decorative borderline), 'Thomas Edison' (deep purple decorative), 'Kelvin Floodlight' (yellow), and 'Penhill Watermelon' (coral and lavender).
When do I plant dahlia tubers?
Plant dahlia tubers outdoors after all frost danger has passed and soil reaches 60°F — typically mid-May in USDA zone 6, late May in zone 5, early April in zone 8. To get a head start, pot tubers indoors in 1-gallon containers 4 to 6 weeks before your last frost date, then transplant out after frost. Tubers planted in cold wet soil rot — wait for warmth.
Do I need to dig up dahlias for winter?
In USDA zone 7 and colder (most of the US Midwest, Northeast, northern UK, and Scotland), yes — lift tubers after the first hard frost, dry for 1 to 2 weeks, and store in dry sand or vermiculite at 40 to 50°F. In zone 8 and warmer (much of the UK south of Manchester, US Southeast, parts of Pacific Northwest), tubers can stay in the ground under 4 to 6 inches of mulch. Heavy clay soils need lifting regardless of zone because cold + wet kills tubers faster than cold alone.
How tall do dahlias grow?
Height varies dramatically by cultivar. Miniature edging dahlias stay 18 to 24 inches tall. Mid-height border dahlias reach 3 to 4 feet. Tall and giant dinnerplate dahlias grow 4 to 6 feet tall and need stakes installed at planting time. Always check the cultivar tag before planting — staking a mature dahlia damages the brittle stem and tuber.
Why don't my dahlias flower?
Five most common causes. First, insufficient sun — dahlias need 6 to 8 hours of direct sun. Second, too much nitrogen — high-nitrogen fertilizer pushes leaves at the expense of flowers; use a low-nitrogen high-phosphorus and potassium feed. Third, no pinching — pinch the central shoot at 12 to 18 inches to force branching. Fourth, no deadheading — once dahlias set seed, they stop blooming. Fifth, planted too early in cold wet soil — wait until soil reaches 60°F.
How long do dahlias bloom?
Most dahlias bloom from mid-July through first frost — roughly 12 to 16 weeks of continuous flowers if you deadhead. In cool UK summers, dahlias may flower from June into November in mild years. Each cut-flower stem holds 1 to 2 weeks in a vase. Single, anemone, and collerette forms tend to bloom earliest in the season; large decoratives and cactus forms peak from August through frost.