Step-by-Step Growing Guide
Dahlias grow from tuberous roots planted in spring after the last frost when soil reaches 15°C. Plant tubers horizontally 10–15cm deep with the eye (growth bud on the neck, not the tuber itself) pointing upward, spacing 60–90cm apart for large dinner-plate types, 30–45cm for patio types. Dahlias demand well-drained, fertile soil with pH 6.0–7.0 and full sun for at least 6–8 hours. Do not water until shoots emerge above the soil — the tuber can rot before it sprouts if kept too wet. Once growing actively, water deeply at 2.5–4cm per week. Feed with a low-nitrogen, high-phosphorus and high-potassium fertilizer every 2–3 weeks once established. Pinch the growing tip when plants reach 30cm tall — pinch again after 4–6 more weeks for maximum branching. Stake all tall varieties before they need it. Dig tubers before first frost, cure in dry conditions for a week, and store in damp peat or vermiculite at 5–10°C.
