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Cosmos - Care Guide
Cosmos atrosanguineus - Care Guide
This is a reasonably hardy tuberous perennial originating in Mexico which has become a popular bestseller because of its chocolate scented flowers. It has a fairly short lifespan but is easily propagated from basal root cuttings taken in early spring and brought into growth with bottom heat.
Other varieties of cosmos (which we do not stock) are annuals for the summer border display and fillers for the herbaceous border. C. atrosanguineus are excellent border or container plants and, more importantly, perennials.
This plant is initially erect in its growth habit but soon ‘flops’ and spreads. The plants which we sell in pots at shows require careful tying in to small split cane supports but this is not necessary when they are grown in a border.
The stems are reddish-brown with spoon-shaped, pinnate, dark green leaves. Individual cup-shaped flowers which are velvet centred and chocolate-maroon in colour with darker brown florets appear from midsummer to autumn.
The maximum height of the plant including the flowering stems is around 2ft with a slightly smaller spread. Deadheading is important in extending the flowering period and a good autumn mulch will help protect the plants in a cold winter. Alternatively, the tubers can be lifted and overwintered in slightly damp peat or leaf mould indoors.