I had tried growing cleomes before, but when I saw them towering in the productive walled kitchen garden at Rousham last September it felt like a challenge.
They are not entirely straight forward to germinate - although they are happy to seed themselves about in the right garden - so they spent a couple of weeks in the fridge ("have you made a chocolate pudding?" my children asked), before going back into the greenhouse, and onwards. The seeds should be on the surface of the compost and ideally in individual cells. I was, eventually, rewarded with nearly 100% success, and was able to give a few away. In retrospect - and as with so many half hardies - it might have been easier to have waited until April when there is more light.
I bought the seed from the wonderful Higgledy Garden.
Pinch out the main stem! This is where I went wrong pre Rousham.
I have used Cleome 'Helen Campbell' (white), Pink Queen, and Violet Queen constantly all summer. They are fantastic for hand tied bouquets, somehow airy but substantial at the same time, and for getting some really good height in a large pedestal arrangement.
BUT.... those thorns. They really are sharp and removing them adds some time to the whole process. Bees love the flowers so watch out for them if picking. And on the subject of wildlife, slugs find them delicious whilst young, despite those thorns.