Growing Great Dahlias

Growing Dahlias

By Cory Kelso, UC Master Gardener

Planting

• Choose a sunny site protected from strong wind. If you live in North County or in a very hot area, provide afternoon shade.
• Dahlias prefer well-drained soil. Prepare soil with a good-quality planting mix to improve drainage in clay soils and water-holding capacity in sandy soils.
• Dahlias grow well in pots. Use a high-quality potting soil.
• Incorporate a fertilizer formulated for vegetables and flowers. Avoid high-nitrogen fertilizers, which promote foliage at the expense of blooms.
• Place a stake in the planting hole for support. Tomato cages also work well.
• Plant tubers horizontally 1–2” deep. Add soil gradually as plants grow.

Watering

• Do not overwater newly planted tubers.
• As plants grow, keep soil evenly moist but never soggy.
• Water needs increase as flowers form, especially during hot weather.
• Reduce watering as fall approaches.

Pests and Diseases

• Slugs and snails can destroy plants overnight.
• Earwigs may feed on leaves and flowers. Keep the area free of debris. Sluggo Plus and spinosad can help control populations.
• Thrips and mites damage flowers and weaken plants. Deadhead frequently and occasionally hose plants off to reduce pests.
• Diabrotica (cucumber beetles) love dahlia flowers. Hand-picking early in the morning is effective.
• Powdery mildew is the most common disease. Provide good air circulation, maintain proper watering and nutrition, and remove infected leaves.

Maintenance During Growing Season

• Feed occasionally during summer if needed.
• Deadhead regularly to encourage continuous blooms.

Dahlia Resources