Growing Dahlias

Pronunciation: dah'lee-uh

Flamboyant summer-to-frost blooms on lush plants. Hardy to Zone 8 (Zone 7 with heavy mulch). Colder zones: start tubers in pots 4–6 weeks before last frost. Plant several inches deep in light soilless mix, water sparingly until growth appears, then freely. Sunny window or grow lights. Transplant after frost danger passes. Stake tall varieties carefully. Delayed planting? Store tubers cool, dry, dark.

Growing Conditions

• Light/Water: Full sun North, afternoon shade South. No water until growth emerges; then deep watering 2×/week.
• Soil/pH: 60°F soil at planting. Open, well-drained, pH 6.5–7.0.
• Fertilizer: Low-nitrogen (5-10-10) at 30 days post-planting, then monthly side-dress. Avoid high-nitrogen water-soluble products.

Pests & Diseases

• Aphids: Insecticidal soap or neem.
• Borers: Stems break/wilt. Keep weeds away; destroy infested stems.
• Leafhoppers: 1 tbsp isopropyl alcohol + 1 pint insecticidal soap, 3× at 3–5 day intervals.
• Spider mites: Hot, dry weather. Neem or forceful cold water spray (undersides).
• Powdery mildew: Whitish coating. Wettable sulfur or fungicide. Next year: more spacing for air flow.
• Stem rot/wilt: Bacterial/fungal. Remove affected parts. Prevent: well-drained soil, no overwater, keep mulch away from stems.

Companions & Care

• Companions: Roses, oriental lilies, annuals, goldenrod, fall asters.
• Pruning for cuts & bushiness: Pinch center shoot above 3rd leaf set. Rooted shoots = new plants. Cut flowers: place stems in 160°F water until cooled.
• Reflowering: Deadhead diligently for continuous bloom. For exhibition size: remove side buds, one bud per stem.
• Dividing: Spring or fall. Sharp knife—only tubers with eyes grow. Halves/quarters safer than individual tubers. Dry 1 day before storing/planting. Label varieties.

End-of-Season Storage

Wait days after frost blackens foliage (or mid-November in frost-free areas). Cut stalks to 4–6", rinse, air-dry 24 hrs under cover. Layer in newspaper-lined boxes/pots with barely moist sawdust, sand, or peat. No plastic. Cool (40–50°F), dry, dark. Check monthly for rot/shriveling—mist lightly if shriveling. Remove all old foliage from garden.

Calendar of Care

• Early Spring: Divide tubers. Plant 6" deep when soil warms or start indoors. Water once, then wait for growth. Fertilize at 2" growth.
• Mid-Spring: Monthly 5-10-10. Watch pests. Control weeds.
• Late Spring: Mulch (away from crowns). Water if dry. Stake tall varieties. Pinch centers or disbud for large flowers.
• Summer: Monitor fungal wilt—remove/destroy, sterilize tools. Watch pests. Water as needed. Deadhead for continuous bloom.
• Fall: Heavy mulch if overwintering in Zones 7+. North: dig after frost, dry, store cool/dry/dark in lined boxes with moist sand/peat. Divide if desired. Label varieties.