Centaurea Macrocephala (Knapweed)
A very long name for our second knapweed. Its a magnificent plant. This time from the US. Growing 3 feet this plant produces large Scottish thistle like flowers in yellow up to 4 inches across. The leaves are attractive and they look wonderful in floral arrangements. I have seen 2 others specimens of this perennial in 25 years – it is listed by the RHS as garden worthy but doesn’t seem to be in production.
Sow indoors. Sow 10mm deep into moist seed compost in a temperature of between 15 and 20°C. This centaurea does not need light to germinate, and is best left in the dark. Germination takes 21-28 days. Transplant seedlings once large enough to handle to small pots. Plant out in the following spring when there is no risk of frost. You can sow direct into prepared, raked soil 3mm deep in drills 30cm apart in the spring.
THEY NEED TO GERMINATE IN THE DARK!
So if you having trouble, this may be why!.