Growing Great Dahlias

By Cory Kelso, UC Master Gardener

Planting

• Choose a site that is sunny and out of strong wind. If you live in North Count or in an area that gets very hot, plant your dahlias where they will get some afternoon shade.
• Dahlias like well-drained soil. Prepare soil using a good quality planting mix.  This will improve drainage in heavy clay soils and improve water-holding capacity in sandy soils.
• Dahlias grow well in pots. Use a good quality potting soil.
• Incorporate a fertilizer that is generally used for vegetables and flowers. Don’t use a fertilizer with a high nitrogen ratio, as that will promote lush foliage at the expense of flower production.
• Place a stake in planting hole.  This will be used to support your plants as they grow.  Tomato cages work well, too.
• Plant tubers horizontally only 1” to 2” deep.  You can add more soil as your plants grow.

Watering

• Don’t overwater newly planted tubers.
• As plants grow, keep soil evenly moist but never soggy.
• Plants will require more water as flowers form, especially on hot days.
• As fall is approaching, cut back on watering.

Pests and Diseases

• Beware of slugs and snails! They love dahlias and can destroy them in one night.
• Earwigs can eat leaves and flowers. Keep area around plants free from weeds and debris where they can hide.  Sluggo Plus and Spinosad can help control.
• Thrips and mites can damage flowers and weaken plants. Deadhead flowers frequently and give you plants an occasional bath to control.
• Diabrotica (Cucumber Beetle) love dahlias flowers. Hand picking in early morning is best control.
• Powdery mildew is the most common disease of dahlias. Make sure plants have good air circulation.  Keep plants well watered and fed during growing season.  Remove infected leaves.

Maintenance During Growing Season

• Dahlias will benefit from occasional feeding during the summer.
• Deadhead to keep those flowers coming!

Dahlia Resources