Dahlias are tender perennials grown for flowers in many colours, shapes, and sizes. They grow from tubers with buds called eyes. A tuber is not a bulb or a rhizome.
- Choose firm, healthy tubers without mold, cuts, or soft spots.
- Plant outdoors after danger of frost has passed and the soil has warmed. Choose full sun, shelter from damaging wind, and soil that drains well.
- Follow the supplier's directions for depth and spacing because dwarf and giant cultivars need very different amounts of room.
- Put a stake in place when planting a tall cultivar so you are less likely to spear its tubers later. Tie growing stems loosely with soft material.
- Water after planting and when the soil surface becomes dry. Do not leave tubers in waterlogged soil.
- A 2- to 3-inch (5 to 8 cm) layer of leaf mulch, wood mulch, or clean seedless straw helps hold moisture and moderate soil temperature. Keep mulch away from stems.
- Removing faded flowers encourages the plant to keep blooming.
Saving Tubers Through a Cold Winter
In places where the ground freezes, dahlia tubers generally cannot stay outdoors through winter.
- After frost kills or dries the foliage, ask an adult to cut back the stems and loosen the soil several inches away from the plant with a fork or spade.
- Lift the whole clump gently. Cuts and bruises give rot an easy way in.
- Gently wash off soil, then cure the clump for one to three days in a dry, ventilated place away from direct sun and drying wind.
- Label each cultivar and store the tubers in cool, dry conditions above freezing. Check them periodically and remove material that is rotting.
- An adult can divide a clump with a clean, sharp tool before planting. Every division needs part of the crown with at least one eye; a loose tuber without an eye will not make a new plant.
Fascinating Facts!
- Dahlias are native to Mexico and Central America.
- The flower forms range from tidy pompons to enormous decorative blooms.
- Some cultivars stay compact enough for containers, while others grow taller than a child.
- Dahlia flowers occur in many colours, but breeders have not produced a true blue one.