Dahlia coccinea has been extensively bred and today's cultivars bear little resemblace to the original plant.
The flowers vary in size, from miniature (< 100mm) to Giant (> 250mm), shape (eg. formal, decorative, cactus, water lily, collarette), and colour (white, yellow, orange, pink, red, purple).
Certain cultivars have more than one colour.
Dahlias are deciduous perennials, growing leaves and stems during the Summer and dying down to a "tuber" in the Winter.
The tuber is actually a swollen root, modified to store food.
Come spring, growth commences from dormant eyes in the crown, fed by the "tuber".
The "tuber" do not have growth eyes and will not grow if detached from the crown.
Plant dahlia tubers in the spring, when the weather starts to warm up and the danger of frosts has passed.
This is usually around late October.
Tubers should have at least one eye.
They can be sprouted several weeks before planting in the greenhouse, then planted with the top of the sprouts just above the soil level.
Pick a spot that gets full sun and has free draining soil.
Add compost to improve the soil structure.
Insert a stake into the ground first, then plant beside the stake.
Plant one tuber per stake for giant varieties, or two tubers per stake for the other varieties.
Do not plant the tuber too deep or the shoots may rot.
Water sparingly until growth commences, thereafter, water everyday when it is dry.
Feed with a balanced fertilizer - grow the dahlias as you would cabbages.
Allow only one main stem per tuber - remove the rest.
Pinch out the growth on the main stem after the 5 set of leaves and allow it to branch.
For larger flowers, pinch out competiting buds.
Dead head regularly to ensure a continuous supply of flowers and to keep the flower size up.
In the autumn, allow seed heads to form.
This will harden growth for the Winter.
Cut back to the ground before the first frost and lift tubers.
Store the tubers in untreated sawdust in a cool but frost free area (such as a garage) to over winter.
Come spring, when the buds begin to swell, the tubers can be split, ensuring each tuber has at least one bud.