Dahlias have somehow acquired the reputation of a diva, and I’d like to formally object. They are the most forgiving thing I grow, and the most generous — one tuber can hand you forty stems before the frost.
Three rules, no more
Plant after the last frost, in the sunniest spot you own. Don’t water until the first shoots show, or the tuber sulks and rots. Pinch the growing tip once at a hand’s height, and the plant will branch into a small factory.
Then cut, constantly. A dahlia repaid in vases is a dahlia that keeps producing; leave the blooms on and it decides its work is done. Doubt yourself all you like — the dahlia won’t.