When you first start growing dahlias, you think you’re just picking some pretty flowers. Then you find out there are more than 20 recognized forms, and suddenly you’re zooming in on petal tips like a detective trying to decide if something is “formal decorative” or “semi-cactus.”
Don’t worry, I’ve been there. Here’s a simple breakdown of the most common dahlia forms you’ll actually see in gardens (and why you’ll end up wanting one of each).
Decorative Dahlias
These are the classic beauties you’ll find in every florist’s cooler. Full, fluffy, and perfectly symmetrical, the kind of flower that makes people stop and ask, “Is that even real?”
They come in two types:
Formal Decorative: Petals are flat and precise, like they practiced their spacing.
Informal Decorative: A little wilder, a little looser, and full of character.
Cactus and Semi-Cactus Dahlias
If the Decoratives are elegance, these are energy. Long, rolled petals give them a spiky, fireworks look.
Cactus: Fully rolled petals with all-out drama.
Semi-Cactus: Partially rolled for a softer texture but still plenty of flair.
They’re incredible in bouquets and bring movement to arrangements.
Waterlily Dahlias
Rounded petals that gently curve inward to mimic a waterlily. They’re calm, graceful, and great for anyone who likes symmetry but not fuss.
Dinnerplate Dahlias
My fav!!!! These are the showstoppers. Huge, jaw-dropping blooms that can reach eight inches or more across. The kind of flower you need to photograph beside your hand (or head in my case haha!) just to prove the size.
They’re heavy and sometimes need support, but when they open, it’s magic.
Ball and Pompon Dahlias
Perfectly round and irresistibly neat.
Ball Dahlias: Golf ball size and often rich in color.
Pompon Dahlias: Smaller, tighter, and extra tidy, like little floral marbles.
They’re long-lasting, have strong stems, and always look professional in arrangements.
Anemone and Collarette Dahlias
These are the personality blooms. They have layers, texture, and a little whimsy.
Anemone: Have a cushion-like center surrounded by larger petals.
Collarette: Have one outer row of petals with a frilly inner ring around the center.
Bees love them, and they add playful variety to the garden.
Single and Orchid Dahlias
Simple, open, and full of charm.
Single Dahlias: One neat layer of petals with a visible center, perfect for pollinators.
Orchid Dahlias: Narrow, twisted petals that look like ribbons caught in the wind.
They’re ideal for mixed gardens or anyone who loves that “perfectly imperfect” look.
Novelty and Specialty Forms
These are the rule breakers. They might twist, streak, or change colors as they bloom. Every one is unique and a reminder that even in a field of perfectionists, there’s always room for the rebels.
Final Thoughts
No matter the form, whether spiky, round, or wild, dahlias have a way of stealing your heart (and maybe your storage space).
So start small, they said. Just a few, they said.
And here we are, surrounded by far too many dirty tuber clumps waiting to be divided before their winter slumber.
But honestly, there are worse addictions. 😉