How to Grow Chocolate Cosmos

Chocolate cosmos is a flower to whet any gardener's appetite. These unique blooms are a rich, dark maroon with velvety rounded petals and dark brown centers. Their best characteristic may be their chocolaty fragrance. Similar to regular cosmos, the flowers of chocolate cosmos are a bit smaller, measuring an inch and a half across. The overall effect is very dramatic, making these flowers highly sought after for garden beds, containers, and floral arrangements. They pair especially well with all shades of pink flowers, creamy white flowers, and blue shades to offset the brown tones. They hold up well as cut flowers too.

This highly-sought after flower was first introduced commercially in 1885, in a seed catalog. However, most varieties produce sterile seeds, so these cosmos are propagated via tuberous roots, similar to the roots of dahlias. Native to Mexico and rumored to be extinct in the wild for decades, chocolate cosmos was found in old oak and pine forests in the early 21st century. In recent years, several new cultivars have been introduced.

The chocolaty fragrance of chocolate cosmos is due to the presence of vanillin, an organic compound also found in cocoa. The scent is most pronounced on warm days. Plant them in containers near a patio or seating area to enjoy the fragrance more easily.

Chocolate Cosmos Care

These flowers behave much like regular cosmos despite their differences. They benefit from deadheading to keep the blooms looking neat, and will usually keep producing new flowers until the first frost. They are hardy as perennials in Zones 9 and above, but with heavy mulching and winter protection, you may have luck growing them as perennials in Zones 7 and 8. The plants may take a couple of years to get established, but as they increase in size they will produce more flowers in season. Divide chocolate cosmos in spring or autumn.

Light

Like regular cosmos, chocolate cosmos likes plenty of direct sunlight, at least six hours per day.

Soil

Well-drained, fertile soil will allow these beauties to flourish. If growing in containers, a mix of potting soil and topsoil should yield good results, perhaps adding some pebbles in the bottom of the container to ensure good drainage.

Water

Too much water can cause their roots to rot, so be careful not to overwater. A deep watering once per week in summer, unless there is a lot of rain, should be sufficient. Allow the soil to dry out slightly between waterings.

Temperature and Humidity

These flowers can be frost sensitive, so avoid planting before all danger of frost has passed. They can handle humidity and enjoy moist soil, but too much water at their roots can cause rot.

Fertilizer

Too much fertilizer might cause your chocolate cosmos to produce more foliage than blooms, but a bit of rose food applied in spring can help these flowers achieve and maintain their vibrant color through to autumn.

Propagating Chocolate Cosmos

The seeds of chocolate cosmos are sterile, so they won't reseed or produce plants from seed. The only way to propagate these flowers is via a root cutting or planting. The roots are thick and tuberous; look for root sections that have "eyes" or buds of new growth for the most successful plant starts.

Overwintering

Chocolate cosmos are grown as an annual in colder climates, but the roots may be dug up in autumn and stored for winter as you'd store any other root annual such as a canna or dahlia, and replanted in spring. In warmer climates where they grow as perennials, give them a good coating of natural mulch to protect the roots for winter.

Common Pests and Diseases

The following problems may plague your chocolate cosmos: Powdery mildew, stem canker, Rhizoctonia stem rot, gray mold, and aphids. Give them plenty of space and air flow to prevent powdery mildew.