There are about 30 dahlia species, and each one offers an explosion of color for your garden. Dahlias can have disk- or ray-shaped flowers in purple, red, white or yellow -- depending on whether they're ornamental or wild. Most have segmented and toothed leaves. These striking flowers can be grown from seeds or tubers. Just sprinkle seeds over potting soil in a low, flat container. Then, lightly cover with more potting soil, making sure to water it carefully. Sprouts will pop up in less than two weeks. Tubers, on the other hand, need to be planted when the ground temperature is about 60 degrees Fahrenheit (15.5 degrees Celsius), which is anytime from mid-April through May for most parts of the country. Plant dahlias where they'll soak in at least eight hours of sunlight per day; less sunlight translates to taller plants with fewer flowers. Soil should be well-drained and slightly acidic (6.5 to 7.0 pH).