Cosmos bipinnatus Sensation Purity is probably the best of the white-flowered Cosmos which is why it was the first choice in our range of ready to plant cosmos seedlings.
It really is a fantastic plant. Like most of its family, you could be forgiven for growing Cosmos Purity for its foliage alone - fresh green and finely cut - almost like extra lush Dill. It is a much more powerful plant though producing a staggering number of large, white, daisy-like flowers from late spring through to autumn. It looks at its best in a mass planting - about a dozen is a good number, but it also a makes a very good subject in a container along with one of the larger Verbenas and/or some Lavender plus a silver foliage plant such as Cineraria, and maybe some white lobelia... or Bacopa...
The trick with Cosmos Purity is to keep it cut and/or dead-headed. As long as it does not run to seed, a single plant can produce well over 100 flowers in a summer which for its - and their - size has to make it one of the most floriferous plants there is. Cutting should not be a problem, it is a superb cut flower and almost trouble free. Really, no garden should be without it.