Viola Network Improved seeds are perfect to add exotic colour for your bedding displays and mixed containers. This hardy perennial is most often grown for reliable early or late season colour. Indoor sowing: Sow thinly in trays of seed compost, cover with a fine layer of compost, firm gently and keep moist. Cover tray with glass, polythene or propagator lid . Seedlings usually appear in 14-28 days. Growing on, remove cover when seedlings appear. When large enough transplant 5cm apart in trays.