Dahlia
Dahlia pinnata
Tuberous perennial producing stunning blooms in an incredible range of forms and colors. Lift tubers before frost in cold climates.
Overview
Companion Planting
Sunflower
MarigoldToxicity
Contains phototoxic polyacetylene compounds that can cause mild gastrointestinal upset and skin irritation in pets; generally considered non-toxic to humans (tubers are historically edible).
Planting Tips
1 cm of water per m² equals 10 liters. Use the Watering Calculator for exact amounts.
Care Tip: Pinch the central growing tip when plants reach 30 cm for bushier growth; stake tall varieties and deadhead spent blooms regularly.
Common Pests
Aphids
Symptoms: Sticky honeydew on leaves, curled or distorted new growth, and sooty mold.
Treatment: Spray with insecticidal soap or neem oil; dislodge with a strong water jet.
Prevention: Encourage beneficial insects such as ladybugs and lacewings; avoid excessive nitrogen fertilization.
Slugs and Snails
Symptoms: Irregular holes in leaves and petals, silvery slime trails on and around plants.
Treatment: Use iron-phosphate slug pellets or beer traps; hand-pick in the evening.
Prevention: Remove garden debris and mulch away from stems; use copper tape barriers around pots.
Earwigs
Symptoms: Ragged, chewed holes in petals and young leaves, often worst on blooms.
Treatment: Trap with upturned pots stuffed with straw placed on canes near plants; remove and dispose of caught insects.
Prevention: Clear plant debris where earwigs shelter during the day; avoid thick mulch near dahlia stems.
Common Diseases
Powdery Mildew
Symptoms: White, powdery fungal coating on upper leaf surfaces; leaves may yellow and drop prematurely.
Treatment: Apply a sulfur-based or potassium-bicarbonate fungicide; remove and destroy heavily affected foliage.
Prevention: Ensure good air circulation by spacing plants adequately; water at the base rather than overhead.
Dahlia Mosaic Virus
Symptoms: Light-green mosaic or banding patterns on leaves, stunted growth, and reduced flowering.
Treatment: No cure exists; remove and destroy infected plants immediately to limit spread.
Prevention: Control aphid vectors with insecticidal soap; buy certified virus-free tubers and sterilize cutting tools.
Botrytis Blight (Gray Mold)
Symptoms: Gray, fuzzy fungal growth on buds, flowers, and stems; affected parts become soft and rot.
Treatment: Remove and dispose of all infected plant material; apply a copper-based fungicide in persistent cases.
Prevention: Avoid overhead watering and dense planting; promptly remove spent blooms and damaged tissue.