Cosmos Species, Black Cosmos, Chocolate Cosmos

Cosmos atrosanguineus

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Cosmos (KOS-mus) (Info)
Species: atrosanguineus (at-ro-san-GWIN-ee-us) (Info)
Synonym:Bidens atrosanguinea
Synonym:Cosmos diversifolius var. atrosanguineus



Tropicals and Tender Perennials

Water Requirements:

Average Water Needs; Water regularly; do not overwater

Requires consistently moist soil; do not let dry out between waterings

Sun Exposure:

Full Sun



Foliage Color:

Unknown - Tell us


18-24 in. (45-60 cm)


24-36 in. (60-90 cm)


USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

USDA Zone 10a: to -1.1 C (30 F)

USDA Zone 10b: to 1.7 C (35 F)

Where to Grow:

Unknown - Tell us



Bloom Color:


Bloom Characteristics:

Flowers are fragrant

Bloom Size:

Unknown - Tell us

Bloom Time:

Late Spring/Early Summer

Mid Summer

Late Summer/Early Fall

Mid Fall

Late Fall/Early Winter

Other details:

Unknown - Tell us

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Patent Information:


Propagation Methods:

By dividing the rootball

Seed Collecting:

N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed


This plant is said to grow outdoors in the following regions:

Albany, California

Arroyo Grande, California

Citrus Heights, California

Hydesville, California

Madera, California

Napa, California

Salinas, California

San Francisco, California

San Jose, California

Naugatuck, Connecticut

Wilton, Connecticut

Washington, District of Columbia

Carrollton, Georgia

Valdosta, Georgia

Divernon, Illinois

Cambridge, Massachusetts

Manchester, New Hampshire

Mount Laurel, New Jersey

Corvallis, Oregon(2 reports)

Portland, Oregon


Conway, South Carolina

Collierville, Tennessee

Austin, Texas

Lubbock, Texas

Sugar Land, Texas

Tyler, Texas

Vernal, Utah

CHIMACUM, Washington

Kalama, Washington

Langley, Washington

Seattle, Washington(2 reports)

Spokane, Washington

Tacoma, Washington

show all

Gardeners' Notes:


On Jul 7, 2020, JennysGarden_TN from Collierville, TN wrote:

My Chocolate Cosmos is putting out its first bloom today. Last winter I covered the plant with frost blanket and im so happy to see that it had returned this spring in my zone 7b garden.


On Aug 14, 2015, herbmar from Nanaimo,
Canada wrote:

This is the 2nd year's bloom of my Chocolate Cosmo.
I grow it in a container on my deck, it wintered very well, being cut back, covered with straw and set next to my house on the deck.
I am delighted with this plant; the lush compactness of foliage, strong stems standing tall to boast plentiful gorgeous brown-maroon blossoms that smell faintly of chocolate, as the name implies. Just now, after deadheading, I counted 32 blossoms! with many buds waiting to spring forth. Last year it bloomed profusely until late September. The size and tidy foliage make it the perfect deck plant.
I was disappointed to notice faint tinges of mildew as I deadheaded, the plant had none last year. I will spray it with a fungicide and hopefully dispel the gray mildew. I would dislike los... read more


On Jan 27, 2015, coriaceous from ROSLINDALE, MA wrote:

I've seen this species in many plantings around Boston, MA z6a (generally in planters rather than in the ground), and I've never seen a lot of flowers---at best, one or two per plant. Perhaps it's because people overfertilize their pots, as it's said that fertilizer tends to promote vegetative growth at the expense of flowering.

The fragrance is faint at best, and it doesn't smell much like chocolate to me. I suspect that the perceived resemblance is largely the product of suggestion.

And the flowers are a dark maroon-brown, which makes them visually inconspicuous. The photos showing clear red flowers have color distortions or have been photoshopped.

This is yet another plant that's been overhyped in the gardening press.


On Jan 27, 2015, bluespiral from (Zone 7a) wrote:

This plant has produced seeds, and seeds are sometimes for sale by JonnaSudenius. Her website is on her DG member page.


On Jun 6, 2010, gary1173 from Sugar Land, TX wrote:

I planted a chocolate cosmos in my garden this spring. It grew about a 18" tall, with tiny, 1 inch deep maroon-to-brown blooms atop long stems. Both the color and scent are very reminiscent of chocolate (to me, it smells just like a Tootsie Roll candy). My kids loved it. Unfortunately, my plant broke off at the base in a strong wind during a storm. The root is still in the ground, but I don't expect it to grow back. I loved it so much, though, that I will definitely plant more of these next year.


On Sep 30, 2008, clareb from Missoula, MT (Zone 5a) wrote:

The color of these flowers is more chocolaty than their fragrance. For a real treat, I'd like to combine this plant with Berlandiera - which has a MUCH stronger chocolate fragrance.
Great "see through" stems allow these flowers to combine well with other plants.
Grown in a container in full sun - does tend to wilt during hottest part of the summer but wilt can be relieved by some additional water. Started to bloom in earnest at the end of August. Powdery mildew has been kept in check with fungicide.


On Jan 15, 2008, Fledgeling from Huron, SD wrote:

Contrary to what someone else said here, this clone is NOT of European origin. This self-sterile species is EXTINCT in the wild [Mexico] and only survives in one clone, so it is completely STERILE. No seeds are produced by this species for reasons stated above; propagation is by division and cutting, or micropropigation


On Apr 26, 2006, Leehallfae from Seattle, WA wrote:

My Chocolate Cosmos thrive in full sun.

They have an aroma like that of a cup of hot cocoa. They also have a deep red color. Very nice.

Wanted to add that, even now, in October, 2007, they are still blooming, in a container, in shade.


On Oct 12, 2005, romandoguinn from Albany, CA (Zone 10a) wrote:

I've had a lot of trouble with mildew as well; I usually end up having to cut it way back and let it start over. My climate doesn't require lifting for winter (zone 9b/10a) though. I still give chocolate cosmos a positive rating because it's just so dern cool! Really does smell good! Petals are super velvety and ultra rich.


On Aug 10, 2005, StarDancer from Owen Sound,

Zone 5, Owen Sound, Ontario. Canada. My second year with chocolate cosmos.
I started last year with 10 of them, and I am down to 7. Not the plant's fault. I learned from trial and error, when lifting the tubers for winter storage, do NOT store more than one per pot. (they grow during the winter months, which is why you have to keep them moist.) The ones I put "together" did not grow.
I bring them out in March/April and set them inside in a sunny location and start giving them regular water. By the time "May 24" weekend arrives, I have a good 6 inches of green leaves, and they start blooming by mid June/early July. (we had late snow this year, so they are a bit stunted but bushy and healthy!)
I will pick them out and put them in their own pots before first frost, and... read more


On Jul 25, 2005, Chuck1260 from Arroyo Grande, CA wrote:

Good plant, blooms a long time. Dies back in the winter and returns in the summer. Subject to some mildew. Deadheading improves the duration of bloom.


On Jul 9, 2005, fluffygrue from Manchester,
United Kingdom (Zone 8a) wrote:

I love this plant! It overwintered fine here in Northern UK in poor, well-drained soil, but struggled to regrow as slugs kept nibbling the juicy new shoots, so I decided to pot it up at that point. Beautiful and hassle-free, and looks lovely with lambs' ear plant.


On Sep 23, 2004, Kim_M from Hamburg, PA (Zone 6b) wrote:

I really like the smell of the flowers because they smell like Hersheys chocolate. I have found they are very easy to root. I have accidently broken off pieces and put them in water. They rooted very well. Unfortunately for some reason my Chocolate Cosmos do not like full sun. The foliage suffers and droops all day long. Even when the soil is moist. I have moved them to a moist part shade garden and no more droopy leaves :-D


On Sep 13, 2004, shemcnamara from Colorado Springs, CO wrote:

I was living in Tacoma, Wa. where the pant grew wonderfully. I found it at a local nursery. It did need to be covered with hay in winter or brought in the gararge and water every two weeks. I left one out and unprotected it died.


On Aug 22, 2004, saya from Heerlen,
Netherlands (Zone 8b) wrote:

I'm very fond of this plant. Well...the scent is a bitter chocolate one and of course its colour..a maroon/reddish brown gives you that expectation too. I think the colour strengthenings the chocolate scent...I have it in my garden for several years now. It starts flowering early summer and does not stop doing this untill it gets to cold to flower. It needs warmth and sun to flower.During winter/autumn I'll bring it in dry and frostfree place. I think they are some kind of Dahlia because its tubers are the same. I've planted a few tubers (it has made me off-sets) in full ground to see if they'll survive our winter like that. I leave my Dahlias in full ground and they are blooming every summer for me. European climate is becoming milder because is warming up. The Dutc... read more


On Apr 17, 2004, gmartin from Portland, OR wrote:

I set this plant out in the early summer and had a great show of blooms through out the season and into early fall. Our area gets very warm in summer and we had 2 to 3 ft of snow for days in January. I feared I had lost it but last week began to come back and is now well returned. Gary, Portland OR


On Mar 21, 2003, zeara wrote:

Hi everyone: )

I'm in zone 9 and thinking of using Chocolate Cosmos in a large rock garden between the rocks. Does anyone feel it would work properly?

ps, I'm not sure if this is the area, or if there is an area to ask questions, please feel free to direct me to the proper area.
thank you for everyone taking their time, this site is a HUGE help and a wonderful find for me: )


On May 22, 2002, fcluck wrote:

Cosmos will flourish in regular, well drained, moist garden soil in a position that is well sheltered from strong winds. they love the sun. If the soil is too fertile, the plants will produce an abundance of foliage at the expense of the flowers


On Mar 4, 2002, gringo from Hampton, VA wrote:

The clone of this Cosmos, that is of European origin & widely available, is apparently sterile.
I have grown this from seed, found in a packet of inexpensive wild flower mixed seeds. (American source)


On Sep 20, 2001, Evert from Helsinki,
Finland (Zone 4b) wrote:

Very lovely plant, loved the scent. The roots didn't overwinter for some reason, I moved them inside before the frost came.


On Nov 7, 2000, jody from MD &, VA (Zone 7b) wrote:

This species of perennial cosmos is clump forming, grows to about 2' high. Flowers smell like chocolate and are usually dark maroon/red in color. Blooms in summer to autumn. Roots can be lifted and stored through winter. Hardy zones 8-10.