1. Planting should happen in spring after all danger of frost is gone
2. Space the tubers 3-4 ft apart for large dahlias or 2 ft. apart for smaller dahlias
3. Dig a 12 x 12 inch deep hole (30 x 30 cm)
4. Mix organic matter to the soil that has been removed
5. Fill the hole with the above mix to a depth of 6 inches
6. Put in the tuber horizontally, eye facing upward
7. Cover it with the remainder of the soil
8. Press the soil down around the roots and water the planting area thoroughly
9. When the sprout emerges from the ground, gradually add more soil mix until the hole is totally filled.
★ Dahlias thrive on regular rainfall in most areas, though will require watering in arid and desert climates.
★ Dahlias grow in fertile, humus-rich, well-drained soils.
★ Feed monthly with bloom type fertilizer to ensure full blooms
★ Pinch back new growth when the dahlia is a foot high (30 cm) to promote a compact, bushy growth
★ Remove spent blooms to encourage new blooms
★ The stalks are woody, so aphids can attack them. A spray with insecticidal soap or even physically washing the aphids off a few times with a strong jet of water usually solves this.
★ Cut back almost to ground level in the fall, before lifting and storing for the winter.
★ In USDA zone 9 dahlias can be treated as perennial hardy bulbs and left in the ground. In zones 7-8 and below, dahlias either need to be lifted and stored for winter in a dry and cool place - between 50°F and 60°F (10°C and 15°C), or treated as annuals with new tubers or bedding plants planted each spring.
★ If you decide to leave the dahlia tubers in the ground over winter, apply a 6 - 12 inches of mulch over the ground