Dahlia Source

    ADS Classification Guide

    The American Dahlia Society recognizes 21 official bloom forms and 15 color classifications. This visual reference helps you identify and classify any dahlia you encounter.

    Bloom Forms

    Each bloom form is defined by petal arrangement, petal shape, and whether the center disc is visible. Here are all 21 ADS-recognized forms.

    Formal Decorative (FD) dahlia bloom form

    Formal Decorative (FD)

    Fully double blooms with flat, broad, evenly arranged petals that curve slightly toward the stem. No open center visible.

    Informal Decorative (ID) dahlia bloom form

    Informal Decorative (ID)

    Similar to formal decorative but with irregularly arranged petals that may twist or curl, giving a more relaxed appearance.

    Cactus (C) dahlia bloom form

    Cactus (C)

    Fully double with long, narrow, pointed petals rolled back (revolute) for more than half their length. Creates a spiky, dramatic effect.

    Semi-Cactus (SC) dahlia bloom form

    Semi-Cactus (SC)

    Broad-based petals that revolve (roll back) for less than half their length. A bridge between decorative and cactus forms.

    Ball (BA) dahlia bloom form

    Ball (BA)

    Fully double, ball-shaped blooms with spirally arranged petals that are blunt or rounded at the tip. Over 3.5 inches in diameter.

    Pompon (P) dahlia bloom form

    Pompon (P)

    Miniature version of the ball form, fully double and globular. Blooms must be under 2 inches in diameter.

    Waterlily (WL) dahlia bloom form

    Waterlily (WL)

    Fully double with broad, flat petals that are slightly curved upward, giving the appearance of a water lily floating on a pond.

    Anemone (AN) dahlia bloom form

    Anemone (AN)

    One or more outer rings of flat ray petals surrounding a dense, pincushion-like group of elongated tubular disc florets.

    Collarette (CO) dahlia bloom form

    Collarette (CO)

    A single outer ring of flat ray petals with an inner ring of shorter, contrasting-colored 'collar' petals, and an open center.

    Single (S) dahlia bloom form

    Single (S)

    One outer ring of petals (ray florets) surrounding an open center disc. Simple, daisy-like blooms. 9 or fewer petals.

    Orchid (O) dahlia bloom form

    Orchid (O)

    Single blooms where the ray petals are uniformly involute (rolled forward) for at least two-thirds of their length.

    Peony (PE) dahlia bloom form

    Peony (PE)

    Two to five rows of ray petals surrounding an open center. A fuller version of the single form.

    Stellar (ST) dahlia bloom form

    Stellar (ST)

    Fully double with narrow, elongated petals that curve and twist along their length, creating a star-like appearance.

    Incurved Cactus (IC) dahlia bloom form

    Incurved Cactus (IC)

    Cactus-type petals that curve inward toward the center of the bloom rather than revolving backward.

    Laciniated (LC) dahlia bloom form

    Laciniated (LC)

    Petals are uniformly split or fringed at the tips, giving a finely cut, feathery appearance. Can appear on various base forms.

    Mignon Single (MS) dahlia bloom form

    Mignon Single (MS)

    Single-flowered dahlias on plants that do not exceed 18 inches in height. Compact garden performers.

    Double Orchid (DO) dahlia bloom form

    Double Orchid (DO)

    Fully double blooms where the petals are uniformly involute (rolled forward) for at least two-thirds of their length.

    Novelty Fully Double (NX) dahlia bloom form

    Novelty Fully Double (NX)

    Fully double blooms that do not fit any other classification due to unique petal characteristics.

    Novelty Open (NO) dahlia bloom form

    Novelty Open (NO)

    Open-centered blooms that do not fit standard open-center classifications.

    Miscellaneous (MS) dahlia bloom form

    Miscellaneous (MS)

    Blooms that do not conform to any of the defined classification types.

    Botanical / Species (BO) dahlia bloom form

    Botanical / Species (BO)

    Wild dahlia species and their direct hybrids. Includes D. coccinea, D. merckii, D. imperialis and others.

    Color Classifications

    The ADS uses 15 color classes to categorize dahlias. Blends, bicolors, and variegated patterns each have their own designation.

    White (W)
    Yellow (Y)
    Orange (O)
    Pink (PK)
    Dark Pink (DP)
    Red (R)
    Dark Red (DR)
    Lavender (L)
    Purple (PR)
    Light Blend (LB)
    Bronze (BR)
    Flame (FL)
    Dark Blend (DB)
    Variegated (V)
    Bicolor (BI)

    Size Classifications

    Size is measured by bloom diameter. The ADS size code is part of every variety's official classification number.

    AA — GiantOver 10 inches
    A — Large8–10 inches
    B — Medium6–8 inches
    BB — Small4–6 inches
    M — MiniatureUnder 4 inches
    BA — BallOver 3.5 inches
    MB — Miniature Ball2–3.5 inches
    P — PomponUnder 2 inches
    MS — Mignon SingleUnder 2 inches, single

    Ready to explore varieties by form, size, or color?

    Browse the Variety Directory