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 dark red blossoms have velvety petals and almost black centers.
START WITH A BETTER PLANT
Chocolate cosmos (Cosmos atrosanguineus) are grown from dahlia-like tubers. Longfield Gardens supplies grade #1 tubers that are propagated in Holland.
SUN AND HEAT: Chocolate cosmos should be planted in a warm, sheltered location with all day sun. In northern areas you may want to give them a head start by planting the tubers in pots several weeks before bringing them outdoors.
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 the plants a warm, sunny spot on your deck or patio. Growing in containers will also give the soil an extra boost of heat and make it easier to enjoy the beauty and fragrance of the flowers up close.
The daisy-like flowers of chocolate cosmos measure 1½” across and are very attracive to butterflies. Their vanilla-chocolate scent is most pronounced on warm, sunny days. The plants grow 24-30” tall and have an upright but spreading habit, with wiry stems.
Chocolate cosmos are drought tolerant and should not be overwatered. Avoid fertilizer, which will encourage the plants to produce foliage rather than flowers. Make sure to remove spent flower heads so the plants continue setting new buds.
Cosmos atrosanguineus grows 23-30” tall and has 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.
In zones 9-11, where Cosmos atrosanguineus is 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, dig the tubers 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 will usually get a larger plant and more flowers the next year.