Pinch out the growing tip to promote bushy growth.
Removing the spent flowers as the blooms fade will promote moe buds
Start in compost filled seed trays in very early spring indoors
Sow thinly but do not cover with compost. Firm in and keep moist. Cover with a sheet of glass or perspex and keep at 20 to 25C
Remove the cover when the seeds begin to grow
By our calculations, you should look at sowing Blue Danube about 49 days before your last frost date.
Transplant the seedlings to 5cm apart and continue under glass until all danger of frost has past. Harden off and plant out 15cm apart into the final flowering position
Ensure that temperatures are mild (minimum night temperatures should be around 15°C / 59°F) and all chance of frost has passed before planting out, as Blue Danube is a half hardy plant.Blue Danube holds the RHS award of Garden Merit and as such performed better than other similar cultivars for flowering ease of growth and weather resistance