The Cactus Dahlias are mostly large plants, like the Dinnerplates and Semi-Dinnerplates (growing between 3 and 5 ft.) with each stem producing multiple blooms. Many gardeners favor the cactus blooms with their tubular petals that form the famous "fireworks" flowers. They are a sensation in the garden. Why Gardeners love Dahlias (See combination photo below.) Dahlias are one of the most rewarding summer flowers of all. They're really easy to grow with spectacular results. If you know them, you know all about it. If you don't, here is the information you need. Prepare to become "hooked."
First of all, Dahlias are great for cutting, as you can see in the large top photo of an arrangement showing a lavish deep red dahlia right next to a large, voluptuous rose.
Dahlias are native to Mexico, but there's about as much resemblance between the original and the Dutch hybrids as there is between an old toy car and a brand new Mercedes. Dahlias for today's gardeners offer a really big gardening treat.
The "bulbs" are actually tubers, and look a lot like peony roots--sort of like a bunch of carrots. The plants grow quickly and some grow quite tall, always with lush deep green foliage.
Types of Dahlias. These plants have been hybridized into various heights from short bedding plants to tall bushy ones. But they are officially categorized by flower type or shape. The term, "Dinnerplate Dahlia" is probably the most famous description, and though all gardeners use the term, it is not an official classification. "Dinnerplates" are, simply put, the large plants with the huge flowers. The always-double flowers are up to 8", sometimes a whopping 10" across, so the name makes sense.
Photos A and C are examples of Dinnerplate Dahlias. As you can see, they come in both solids and bi-colors.
Photo B shows a whole border of tall dahlias in the garden.
Here are the official classifications:
"Decorative Dahlias" This group includes the Dinnerplates and also other taller (to 4 ft.) plants with double, chrysanthemum-like flowers. The famous "Shogun Dahlias" are as tall as Decoratives, but have very heavy bloom of smaller bi-colored flowers for gardeners who want a large bushy plant covered with color.
"Cactus Dahlias" are the ones with the cactus-like blooms, often in super-bright bicolors, always with the rolled, pointed petals. Like other groups, Cactus Dahlias can be of various heights, as long as they have "cactus" flowers.
"Gallery Dahlias" are a newer group of shorter plants with flower-types of the Decoratives and Cactus groups. The Gallery group is named with terms from the art world including famous artists' names.
"Butterfly" or "Impression Dahlias" are what the Dutch call "bedding dahlias." They stay short, and are perfect for pots or borders. The names in this group all begin with "F" like "Futuro" and "Fantastico". The flowers are wide-open and daisy-like for a really colorful display of their brilliant hues. If well cared-for, watered, and dead-headed, they bloom constantly all season, making great masses of color.
There are other groups such as "Ball Dahlias" and "Pom Pom Dahlias" with spherical blooms, "Colarette Dahlias" with uneven rows of petals creating a "collar" effect--the varieties go on and on. Growing all of them is essentially the same, and best of all, it's easy.
Growing Dahlias: All the gardener needs to do is plant the tubers after spring frosts in good garden soil with full sun. It's best to position them against a wall or be ready to stake them, since they are brittle, and must be protected from high winds. (If you've grown perennial Delphiniums, the plant size and growth is similar, but success with Dahlias is much easier.) Keep them free of bugs, well-watered, and well-fertilized as they grow, and your dahlias will begin to set buds by midsummer and be in full bloom, usually during July or August. Then the huge flowers keep coming until frost.
When frost threatens, just pull the roots up, cut off the stems, and store the tubers until the following spring. Each fall, you'll be amazed how the "bulbs" have multiplied during the summer, giving you more and more to divide and enjoy the next year.
One expert has said, "Never have so many gardeners received so much for so little work, as when they grow dahlias."