Your Guide to Planning, Planting, and Growing Chocolate Cosmos
Who wouldn’t want to grow a flower that looks and smells like red velvet cake? Chocolate cosmos (Cosmos atrosanguineus) have captivated gardeners since they were first discovered in Mexico during the mid-1800’s. Their deep red blossoms have velvety petals and dark centers.
Plan for Success
Chocolate cosmos (Cosmos atrosanguineus) are grown from dahlia-like tubers. We provide grade #1 tubers that are propagated in Holland.
Sun and Heat: Chocolate cosmos are heat-loving plants. They grow best in a warm, sheltered location with all day sun. In northern areas you can give them a head start by planting the tubers in pots indoors, several weeks before moving them outside.
Hardiness: Chocolate cosmos are tender perennials and winter hardy only in zones 9-11. If the plants are grown in very well-drained soil and are heavily mulched, they may survive the winter in zones 7-8. For best results, dig the tubers in fall and store them indoors for the winter where they can be kept cool and dry.
Tips for Growing Chocolate Cosmos
If this is your first time growing chocolate cosmos, consider planting them in a container. This will make it easy to give them a warm, sunny spot on your deck or patio. This will also make it easier to enjoy the beauty and fragrance of the flowers up close.
The daisy-like flowers of chocolate cosmos are 1-2" across. Their vanilla-chocolate scent, which butterflies find irresistible, is most pronounced on warm, sunny days.
Avoid overwatering or overfeeding chocolate cosmos. Too much fertilizer can encourage the plants to produce foliage rather than flowers. Be sure to remove spent flower heads so the plants continue setting new buds.
Chocolate cosmos typically grow 23-30” tall and have an upright but spreading habit. In recent years, several named cultivars have been introduced. Flower colors are slightly different (darker or lighter) than the species and flower size and plant height also vary.
How to Care for Chocolate Cosmos
In zones 9-11, where chocolate cosmos are winter hardy, the plants will die back in winter and re-emerge in spring. Wait until late fall when the foliage has yellowed and then cut them back to the ground.
In zones 4-8, the plants are usually treated as annuals. If you want to save the tubers, treat them as you would dahlias. Dig them up in fall and store them indoors for the winter where they can be kept cool and dry.
If the tubers eventually become crowded, they may be divided. This can be done in fall or spring. Make sure each tuber is attached to some viable stem tissue and has one or more “eyes."
Chocolate cosmos can take several years to mature. If you overwinter the tubers indoors you can expect to get a larger plant and more flowers the second year.
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