D. x hortensis Tall and long lasting A cut flower favourite giving a high percentage of double pompon 'honeycomb' heads. Height: 90cm(36in) Plant Class: Half Hardy Perennial (Treat as HHA). Habit: Tall. Sow indoors, February-April. A warm kitchen windowsill is all you need for starting these seeds. Sow, 0.5cm (?") deep, in trays of compost. Water well and place in a warm position. A temperature of 15-20?C (60-68?F) is ideal. Keep moist. Seedlings usually appear in 14-28 days. Transplant them, 5cm (2") apart, to other trays when large enough to handle (always hold by a leaf, never by the stem). Grow on in cooler, but not cold conditions. Gradually accustom young plants to outside conditions (avoid frosts), before planting out, May-June, 30cm (1') apart, into well-drained soil, when frosts are over. Flowers: July-October.