Sensation Purity Cosmos Plants

• Variety: Cosmos bipinnatus 'Purity' (Sensation series)
• Common name: Cosmos / Cosmea / Mexican Aster
• Type: Half-hardy annual
• Flower form: Single
• Colour: Pure white with a golden centre
• Height: 90–150 cm (36–60 in)
• Flowering period: June–October
• Position: Full sun (minimum 6 hours)
• Soil: Well-drained, ordinary to poor fertility
• Spacing: 30 cm (12 in)
• Good for cutting: Yes – excellent
• Container suitable: Yes, with support in a large pot
• Sold as: Jumbo plug seedlings, hand-sown by us
• Plant outdoors: After last frost (mid-May in most areas)
• Delivered: Late April to May by next-day courier. Collection from Castle Cary also available

Sensation Purity – The White Cosmos Every Garden Needs

Purity is probably the best of the white-flowered cosmos, and it was the first cosmos we chose for our range. The flowers are large, clean, white daisies with a golden centre, produced in quantities that are hard to believe until you see them. As long as you keep cutting or deadheading, a single plant can produce well over 100 flowers in a summer. For its size, that makes it one of the most floriferous plants there is. It belongs to the Sensation series, the group of cultivars introduced in 1930 that transformed cosmos from a temperamental Mexican import into one of the most reliable summer annuals in British gardens. Most of the Cosmos bipinnatus varieties we grow today descend from that original Sensation breeding, and Purity carries the family habit: generous, uncomplaining, and in flower from June until the frosts.

At 90–150 cm, Purity is one of our tallest cosmos. The foliage is the typical cosmos finery, fresh green and finely cut, almost like extra-lush dill. It makes a beautiful backdrop on its own, and the flowers, large and open, are a draw for bees and hoverflies all summer. In a border, plant about a dozen for a proper drift. In a large container, try it with lavender and a silver foliage plant like cineraria at the front. Really, no garden should be without it.

Why Purity Is the Universal Companion

White flowers go with everything, and Purity is the default partner for almost every other cosmos in our range. Velouette (crimson-mahogany stripes) needs a plain white foil, and Purity provides it at the same height. Dazzler (deep carmine) against Purity gives you a classic dark-and-light contrast. Candy Stripe (white edged in pink) alongside Purity lets the pink markings stand out against the solid white. It is the one cosmos that belongs in every mixed planting.

Cosmos has a long and surprising history as a useful plant. In Mexico, it was used in traditional medicine as a remedy for jaundice and fevers. In South Africa, the Basotho used it to manage headache and stomach disorders. In Brazil and Indonesia, the leaves were applied to treat malaria. These days it is grown purely for beauty, but the genus has more to it than most gardeners realise. For a cross-category pairing, plant Purity as a tall, airy backdrop behind dark-leaved dahlias like Bishop of Llandaff or David Howard. The white cosmos above dark dahlia foliage is one of the great summer border combinations.

Why Grow Ashridge Cosmos?

We hand-sow every cosmos plug ourselves at our nursery in Somerset and grow them on in our own polytunnels. No contract growing, no outside suppliers. We source the best seed fresh each year because cosmos does not come true from saved seed. Every plant is hardened off before it leaves us.

Your seedlings arrive by next-day courier from late April. If anything arrives damaged or fails to establish, our plant guarantee has you covered. Ring us and you speak to the team in Somerset who grew the plants.

Frequently Asked Questions

How tall does Cosmos Sensation Purity grow?

Purity reaches 90–150 cm (3–5 ft), making it one of the tallest cosmos. Support is not optional at this height. Put it in at planting time. Horizontal netting at 30–40 cm works well for groups; individual canes for smaller plantings. For full growing advice, see our cosmos growing guide.

Is Cosmos Purity good for cutting?

Purity is a superb cut flower. The long stems suit tall vases and the large white daisies last 7–10 days in water. Cut in the morning, take the stem to the first leaf joint, and the plant will produce more flowering shoots in response. A dozen plants, cut regularly, will keep a household in white flowers all summer.

What looks good planted with Cosmos Purity?

Purity is the universal cosmos companion. It pairs with everything: Velouette (stripes), Dazzler (deep carmine), Candy Stripe (bicolour), Apricotta (warm peach). It is also the best tall white cosmos for planting behind dark dahlias. Browse the full range in our cosmos collection.

Can I grow Cosmos Purity in a pot?

Yes, though it is tall and will need a large pot (10 litres minimum) and support. Try it in a generous container with lavender, silver-leaved cineraria, and trailing white lobelia or bacopa for a classic summer display. For full container advice, see our guide to growing cosmos in pots.

Does Cosmos Purity need deadheading?

Yes, and it is the single most important thing you can do for continuous flowering. Cut the stem back to the first leaf joint, not just the flower head. If a plant sets seed, it reads that as job done and stops producing buds within days. Keep on top of it and Purity will repay you with flowers from June to November.