I only started growing spider flowers, Cleome hassleriana, two or three years ago although on the rare times I’d seen them growing in other people’s gardens over the years I was always smitten. I did buy seed a few times over the past few decades but the seed quality was so poor that I had no success in germinating it. It was only when Lambley started importing fresh Cleome seed that I had another shot at growing them.
In warmer climates seed can be sown straight into the garden but as we have very late frosts, often mid to late November, here in the central highlands of Victoria, I sow seed in a poly house in late September on a heated bed set to 21C. Pricked out into individual 7.5cm pots a few weeks later the plants are ready to be put into the garden by late November. Once planted growth is astonishingly quick. By mid-January the Cleomes are 120cm tall and in full flower.
Individual flowers are like large exotic orchids. Each flower head has a dozen or more flowers open at once and one plant will have a dozen or more heads. Cleomes are self grooming with spent flowers dropping to the ground and new flowers taking their place. There is no dead heading to be done. The plants are tidy and productive until the first heavy autumn frosts.
Copious amounts of seed is set and if allowed to drop in the garden may well self sow but it’s best to collect seed, dry it and keep it cool until it’s time to sow again. Fresh seed germinates much better than old seed.
Recently the Sparkler series has been released. This is an F1 hybrid series which produces plants about half the size of older strains. Whilst not so wonderful in large gardens the smaller growing plants are useful for smaller spaces. Whilst seed from these F1 hybrids doesn’t breed true it is still worth collecting your own seed as a good percentage will be dwarf.