Dahlia Seeds

The decorative garden dahlia is a show-stopper, opening big, fully double blooms in rich warm shades of red, orange, pink and gold above bushy, well-branched plants. Grown from seed, these bedding strains give you a varied mix on compact growth that suits beds, borders and large containers, and the more you cut for the vase the more flowers they push out.

Planting

Start seed indoors about 4 to 8 weeks before planting out, sowing roughly 0.6 cm deep into cell trays. Germination is fastest at 18 to 21°C, with seedlings appearing in around 3 to 14 days; heat above 24°C slows it down. Pot on as true leaves appear and never let plants get root-bound. Harden off and plant out about 3 to 4 weeks after the last frost, once nights stay near 13°C, spacing bedding types 23 to 30 cm apart in full sun on sheltered, free-draining soil at pH 6.5 to 7.

Fertilizing

Work in well-rotted organic manure at about 5 kg per square metre before planting. Once growing, feed every two weeks with a potassium-rich liquid feed such as tomato feed to drive flowering, and go easy on nitrogen, which favours leaf over bloom. A phosphorus-rich feed encourages larger, denser flowers.

Care

Water deeply once or twice a week, more in hot, dry spells; on heavy soil irrigate weekly and on sandy soil about every 5 days. When plants reach 20 to 40 cm, pinch out the top 7 to 10 cm for bushier growth. Watch for slugs, snails, aphids and red spider mites, plus powdery mildew in dry air. Blooms follow in roughly 100 to 120 days.