100 seeds 030014 £1.95 In stock
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5 seedlings 510296-5 £5.95 Delivery mid April
When in stock, please allow up to 2 weeks for delivery.
10 seedlings 510296-10 £9.95 Delivery mid April
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15 seedlings 510296-15 £12.95 Delivery mid April
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5 jumbo seedlings 510296-SP05 £7.95 Delivery early May
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Or buy this as part of our The Taj Mahal Collection and Candy Stripe Cosmos Collection.

More Details

Cosmos bipinnatus 'Purity' has large, open flowers of pure white, with delicate apple-green foliage. The classic cut flower and a supremely lovely garden plant, which no one should be without.

Cosmos last 10 days in the vase, produce at least two buckets of cut flowers a week from a 1 x 1m patch and do so from late June until November – so that's nearly fifty buckets of flowers in one season from a small patch. They are impossible to beat.

Genus Cosmos
Group/Species bipinnatus
Variety Purity
Type Half-Hardy Annual
Common Name Cosmos
Border Position Back, Middle
Soil Type Chalky, Neutral
Scent Unscented
Site Full Sun
Moisture Moist but Well-drained, Well-drained
Height 90-100cm (36-39in)
Spacing 45cm (18in)
Sowing, Seeds, Planting Sow under cover in mid spring and plant out after last frosts, or direct sow early May.
Care Tips Pinch out tips at 15-20cm to encourage bushier plants. Needs staking.
Flowering June - October, 12-14 weeks from sowing
Vase Life 7-10 days, no conditioning needed. Pick fresh straight into water, just as the buds are about to bloom, and do not pick in the heat of the day. Deadhead the main blooms that are drooping and going over after about a week. Place out of direct sunlight.
Harvesting Flower production: 4-5 months.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  • Sow Under Cover/Plant Indoors
  • Direct Sow/Plant Outdoors
  • Flowers/Harvest
Advice & Videos
Cosmos summer flower arrangement

In this video, Sarah shows you how to put together a lovely roadside-inspired Cosmos 'Purity' flower arrangement.

Summer flowers for pollinators

This is the time of year for wild dreams when it comes to plans for the summer garden.

Annual flowers – create summer colour

Create summer colour with these unbeatable annual flowers.  Sarah's absolute favourites for reliability and colour.

How to plant and grow cosmos

Even if you only have a tiny garden – or just some pots – you have to grow at least one cosmos. They are the lowest maintenance,...

Direct sowing seeds

Learn how to get great results when direct sowing hardy annual seeds.

How to grow your own wedding: Part 1

In this series, Sarah talks about how she grew the food and flowers for their head gardener, Bea.


Plant Delivery - When in stock, please allow up to 2 weeks for delivery.

Seeds Delivery - Items will be despatched in 5-7 working days.

Click here to find out more information about our delivery rates and times.

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Cosmos bipinnatus 'Purity' reviews

* * * * - Average based on 5 reviews
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Review guidelines

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Goliath Cosmos

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Reviewed 11th April 2018 by Joan Harley

I have also had the same problem with some Cosmos, Purity included, over the past 3 or 4 years. Pinching out does help, but not always. The plants left in large pots (in sun) suffer more than the ones in the beds (semi-shade). They become impressive strong, tall plants, not so feathery, and eventually flower in Septemeber through to the frosts. I have tried not feeding the ones in the pots, it helps but not always. Frustrated that I haven't figured it out though! Good to know I'm not alone!

Cosmos Purity & Dazzler

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Reviewed 17th November 2014 by ELIZABETH WALKER

Grown as usual from seeds sown outside in late April. Transplanted to south facing well drained border. Lots of feathery greenery, and plants grew to 8' but no flowers until September. What was wrong?

Reply from the Sarah Raven Team:

"Thank you so much for your comments. Cosmos really need a lot of sun, and thrive once pinched out, so this may be the reason for the late flowering.

For further information, please contact our Customer Service team or view our Instruction Booklets online."

Posted 18th November 2014

always reliably lovely

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Reviewed 17th November 2014 by mary dunstan

Have grown this from seed for several years, and they always do well, in sunny and not-so-sunny sites. Only in late November are they tailing off. Elegant both in flower and leaves, and an excellent foil to many other plants. A true garden essential.

Cosmos - not good cut flowers at all

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Reviewed 13th August 2014 by Wendy Carter

I grew these cosmos for cut flowers on the basis of this recommendation but am terribly disappointed. Contrary to the claim, I have consistently found that they last only a few days as cut flowers. The ones I cut on Saturday I have thrown out today, Wednesday. this is typical of my experience of them. So just leave them in the garden where they look great.

Reply from the Sarah Raven Team:

"Thank you for your comments. We asked the team at Perch Hill to check this out for us, and this is what they came back with:

"It's now day 6 and I had to deadhead the main blooms that are drooping and going over, but the buds on the stems are now opening so taking over and the foliage still looks very fresh. I would propose that the customer may just be picking one flowering bloom on a stem that's a few days old and then goes over or droops after 3 days. Or if she is picking stems with buds too she is doing something wrong: picking in the heat of the day, picking old blooms, putting on a hot sunny windowsill, cutting the stems and letting the stem ends get dry before putting into water so preventing water uptake."

Make sure to pick fresh blooms, cut the stems straight in to water and they should remain looking really fresh. Make sure to do a bit of deadheading, and in the vase they should last 7-10 days. Let us know how you get on, and you can find further advice at http://www.sarahraven.com/articles/the_basics_of_arranging_cut_flowers.htm"

Posted 20th November 2014

flowery blowsy

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Reviewed 27th June 2014 by Vanessa Wagstaff

Cosmos was one of the first annuals I discovered after studying gardens in books. It worked very well and easily, with a beautiful froth of cut flowers. This year I've been rather late getting them in the ground and they have grown shorter, but normally they are a good 4-5 foot high in richer soil. Just wonderful for the house.