Dahlia Growing Guide

Dahlia pinnata

Crop Rotation Group

Miscellaneous ●

Soil

Rich, fertile soil with excellent drainage.

Position

Full sun.

Frost tolerant

None. Dahlia foliage is killed by frost, and roots are hardy only to about 15F (-9C).

Feeding

Mulch with rich compost in early summer, after new growth appears. Fertilize with a liquid fertilizer in midsummer to support strong re-blooming.

Spacing

Single Plants: 1' 11" (60cm) each way (minimum)
Rows: 1' 7" (50cm) with 1' 11" (60cm) row gap (minimum)

Sow and Plant

Dahlias are often sold as dormant crowns consisting of several connected tubers. Prepare a wide planting hole at least 12 inches (30 cm) deep. Spread out the tubers and plant them 3 inches (8 cm) deep, then add a mulch of compost. A few weeks later after the first stems emerge, hill up a little soil around the base of the plant and begin summer mulching. Allow 24in (60cm) between tall dahlias. Small dwarf varieties can be planted 12in (30cm) apart.
Our Garden Planner can produce a personalised calendar of when to sow, plant and harvest for your area.

Notes

Dahlias will bloom all summer when provided with regular water and fertilizer. The color range is endless, and flower size can be large or small, depending on variety.

Harvesting

Dahlias make excellent cut flowers, so they should be easily accessible. Cut dahlias for arrangements as soon as the blossoms open, preferably in early morning. Immediately plunge the stems into warm water. As the flowers fade in the garden, trim them off with scissors or pruning shears.

Planting and Harvesting Calendar

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Pests which Affect Dahlia

Aphids (General)

Slug

Snail