This Fall-Blooming Perennial Will Fill Your Garden With A Sweet Chocolate Aroma And Rich Color

Looking for something unusual to grow in the garden? Look no further than chocolate cosmos, a tuberous perennial with velvety blooms and a decadent fragrance. With showy wine-red blossoms that perfume the garden with the distinctive aromas of chocolate and vanilla from mid-summer through fall, chocolate cosmos entices butterflies and curious gardeners alike. The blooms make fragrant cutting for the vase and plants perform beautifully in containers, where their scent can be enjoyed on patios and balconies. Bring the beauty and aroma of chocolate cosmos to your own garden by learning how to grow and care for these unique bloomers.

Plant Attributes
Common Name	Chocolate Cosmos
Botanical Name	Cosmos atrosanguineus
Family	Asteraceae
Plant Type	Perennial, Herbaceous
Mature Size	24-36 in. tall, 12-24 in. wide
Sun Exposure	Full Sun
Soil Type	Medium, Well-draining, Average
Soil pH	Slightly Acidic (5.5-6.2)
Bloom Time	Summer, Fall
Flower Color	Wine-Red, Maroon
Hardiness Zones	8-11 (USDA)
Native Area	Mexico
Toxicity	Not Toxic to Humans or Pets

Chocolate Cosmos Care

Chocolate cosmos are native to Mexico and thrive in sunshine and warm soil. They are fairly drought tolerant once established and don’t require much pampering. Chocolate cosmos make a great addition to cottage gardens, butterfly plantings, cutting gardens, and containers. They can be grown outdoors year round in zones 9-11 (8 with protection) and must be lifted for winter storage elsewhere. 

Light

Chocolate cosmos perform best with all day sun. Plant them in a location receiving at least 6 hours of direct sun per day.  

Soil

Good drainage is essential for maintaining healthy chocolate cosmos. Plant them in sandy or loamy soil with average fertility and good drainage.  

Water

Chocolate cosmos tolerate dry conditions once established, but thrive with regular irrigation. Avoid overwatering plants as wet soil encourages root rot. Wait for the soil to dry slightly before watering. 

Temperature And Humidity

The fragrance of these heat-loving plants is most pronounced on warm sunny days. In cool locations, chocolate cosmos perform well in sunny containers which tend to warm more than surrounding planting beds. Plants go dormant during cold weather. Humidity is not a problem for chocolate cosmos.

Fertilizer

Chocolate cosmos are light feeders. Avoid over feeding plants, which encourages foliage to grow at the expense of blooms.  

Types Of Chocolate Cosmos

Until relatively recently, chocolate cosmos was thought to be extinct in the wild and the only available plants were produced through cuttings and root (tuber) divisions. With the rediscovery of wild populations, new introductions of seed-producing varieties have been made. Using seed-grown plants, modern breeding efforts are focusing on expanding the color range of chocolate cosmos and working with plant form. While most chocolate cosmos available commercially are still the generically named 'Chocolate Cosmos' propagated asexually, new varieties are starting to reach garden centers. Watch for more introductions in the coming years as breeding efforts begin to yield results. 

'Cherry Chocolate'

This variety introduces a unique color among chocolate cosmos with its cherry-red blooms. 'Cherry Chocolate' cosmos produces larger flowers than those of traditional chocolate cosmos while retaining the beloved chocolate scent.  

'Black Magic'

'Black Magic' is among the first chocolate cosmos varieties available that produce viable seeds. The blooms are larger than traditional varieties and the plants have a more compact habit. Flowers are burgundy to almost black in color.  

'Choca Mocha'

This compact variety grows just 10 to 12 inches tall and spreads up to 18 inches wide. Maroon flowers are held on thin but sturdy stems.  

How To Grow Chocolate Cosmos From Bulbs (Tubers)

Most chocolate cosmos are sold as bulbs or more accurately, tubers. Tubers are swollen underground organs produced by the plant’s root system. They serve as a place for plants to store water and nutrients. Chocolate cosmos tubers are sold in late winter to early spring, when the plants are still dormant. Plant tubers in outdoor containers or garden beds after the threat of frost has passed.

1. Space tubers 12-18” apart in loose, well-draining soil.

2. Plant tubers 2 inches deep, such that the top of the tuber lies 2 inches beneath the soil surface.

3. Cover tubers with soil and water well. Keep soil evenly moist but not wet.

4. Be patient. Plants can take several weeks to emerge.

How To Grow Chocolate Cosmos From Seed

Chocolate cosmos seeds are expensive, selling for anywhere from $0.50 to $3 per seed. Still, purchasing seeds is cheaper than buying tubers. And growing plants from seed opens the door to greater genetic diversity. Seeds can be sown directly in the garden after the threat of frost has passed or started indoors 6 to 8 weeks before the last frost date. For outdoor sowing, select a planting bed in full sun with loose, well-draining soil.

1. Prepare planting beds by turning the upper 8 inches of soil. Amend with compost as needed and rake the surface smooth.

2. Sow seeds 4 inches apart and ¼ inch deep. If planting in rows for cuttings, space rows 12 inches apart.

3. Keep soil evenly moist but not wet.

4. Seeds emerge in 7 to 14 days at soil temperatures between 60-75˚ F.

5. Thin seedlings to a spacing of 12-15 inches.

Seedlings grown indoors can be transplanted into the garden or outdoor containers after the threat of frost has passed. 

Overwintering Chocolate Cosmos

Chocolate cosmos are reliably winter hardy in USDA zones 9 through 11, where plants die back to the ground in fall and regrow the following spring. Gardeners in zone 8 may have success overwintering plants in the garden by using a heavy layer of mulch to insulate the planting bed. Plants will not
successfully overwinter in heavy or poorly drained soil. Cut the foliage back to the ground in fall after it has turned yellow.  

Although some gardeners in colder areas treat chocolate cosmos as annuals, the tubers can be dug from the ground in fall and stored indoors over the winter. Treat them much like dahlia tubers, storing them in a cool, dry location. Replant tubers outdoors in spring after the threat of frost has passed. You can give plants a jump start by potting them in late winter and letting plants initiate growth indoors before moving them outside. Make sure to slowly harden off (acclimate) plants started indoors to avoid transplant shock.  

Propagating Chocolate Cosmos From Tuber Divisions

Like other tuber-producing plants, chocolate cosmos can be propagated from tuber divisions. Dividing tubers not only produces new plants, but keeps plants from becoming too crowded, which can impact flowering. Tubers that are dug for winter storage can be separated into starts at the time of digging. Separate clumps of tubers into smaller sections, making sure each tuber has one or more “eyes.” In locations where tubers grow outdoors year-round, tubers can be dug and divided in fall or spring.  

Pruning

Young chocolate cosmos plants benefit from pinching back early the growing season. Pinch out the growing tip of plants when they reach a height of 8 inches. This will promote branching and produce a fuller plant. Deadhead plants after flowering to lengthen the bloom season. Deadheading encourages chocolate cosmos plants to produce more flower buds, keeping plants productive.  

Common Pests & Plant Diseases

Although chocolate cosmos are relatively low-maintenance plants, they are susceptible to common insects and plant diseases. None of these cause serious problems in chocolate cosmos. As with many garden plants, aphids occasionally cause problems on chocolate cosmos. Dislodge aphids from plants using a heavy stream of water or treat with horticultural soap or oil. 

Pathogens including powdery mildew, gray mold, root rot, and stem rots/cankers can be a problem from time to time. Planting in a soil with good drainage is the best way to prevent root rot. Provide ample space between plants to encourage good air flow, which reduces the humidity in the plant canopy making it less favorable to foliar diseases.  

Chocolate cosmos don’t require a lot of pampering. If plants are not flowering well, it may be a sign that you are over fertilizing. If you see lush foliage but few flowers, cut back on fertilizer. The most common problem is over watering. Foliage of plants receiving too much water may turn yellow or even wilt. Remember to allow soil to dry between waterings and use your finger to check soil moisture.