Keep track of your plants with reminders & care tips – all to help you grow successfully
My plants
My calendar
My ideas
My advice
For the latest on RHS Shows in 2021, read more
North Yorkshire
Essex
Devon
Surrey
Greater Manchester
General enquiries 020 3176 5800 Mon – Fri | 9am – 5pm
Help us achieve our goals
Make a donation
We have combined these two powerful search tools into a single Find a Plant service searching over 250,000 plant records.
Virtually all of the features of the old searches are still available and in addition we have added several new features to create a more comprehensive and user friendly search experience.
When using this search
Search by plant name, key attributes or both to find plant details and a list of suppliers.
AGM plants have been through a rigorous trial and assessment programme. They are:
This plant will provide nectar and pollen for bees and the many other types of pollinating insects.
It is included in an evolving list of plants carefully researched and chosen by RHS experts. Divided into 3 groups these lists, linked below, are maintained by a team of RHS staff and are reviewed annually.
Give the gift of RHS membership
Other common names chocolate cosmos black cosmos
black dahlia
Synonyms Cosmos atrosanguineus 'Chocolate' Cosmos diversifolius
Bidens atrosanguinea
Family Asteraceae
Genus Cosmos can be annuals or perennials with simple or pinnately divided leaves and large, long-stalked daisy-like flowers in summer
Details C. atrosanguineus is a spreading tuberous perennial, with pinnately divided leaves and bowl-shaped, chocolate-scented, maroon-crimson flower-heads in late summer
Plant range Mexico
Foliage Deciduous
Habit Spreading / Branched
Fragrance Flower
Hardiness
All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets
H3
Full Sun
Aspect South-facing or West-facing or East-facing
Exposure Exposed or Sheltered
Chalk
Loam
Sand
MoistureMoist but well-drained
SoilChalk, Loam, Sand
pHAcid, Alkaline, Neutral
Ultimate height 0.5-1 metres
Ultimate spread 0.1-0.5 metres
Time to ultimate height 2-5 years
Cultivation Grow in a moderately fertile, moist but well-drained soil in full sun. Mulch in autumn; in cold areas lift tubers before first frosts and keep frost-free over winter.
Propagation Propagate by taking basal cuttings in early spring and providing bottom heat
Suggested planting locations and garden types Cut Flowers Flower borders and beds City & Courtyard Gardens Cottage & Informal Garden
Pruning Deadhead to prolong flowering
Pests Generally pest free
Diseases May suffer from foot rot and grey moulds
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
chocolate cosmos
Buy from £7.99 at the RHS Plants Shop
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.