Photo by Melody

PlantFiles: Common Cosmos, Mexican Aster
Cosmos bipinnatus

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Cosmos (KOS-mus) (Info)
Species: bipinnatus (by-pin-NAY-tus) (Info)

3 vendors have this plant for sale.

44 members have or want this plant for trade.

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24-36 in. (60-90 cm)
36-48 in. (90-120 cm)

18-24 in. (45-60 cm)

Not Applicable

Sun Exposure:
Full Sun

Parts of plant are poisonous if ingested

Bloom Color:
White/Near White

Bloom Time:
Late Spring/Early Summer
Mid Summer
Late Summer/Early Fall
Mid Fall


Other details:
This plant is attractive to bees, butterflies and/or birds
Drought-tolerant; suitable for xeriscaping
Average Water Needs; Water regularly; do not overwater
Self-sows freely; deadhead if you do not want volunteer seedlings next season

Soil pH requirements:
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)
7.9 to 8.5 (alkaline)

Patent Information:

Propagation Methods:
From seed; sow indoors before last frost
From seed; direct sow after last frost

Seed Collecting:
Allow seedheads to dry on plants; remove and collect seeds
Properly cleaned, seed can be successfully stored

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11 positives
2 neutrals
No negatives

Gardeners' Notes:

Positive Dosetaker On Sep 7, 2012, Dosetaker from Mason, NH (Zone 5b) wrote:

Love their tendency to self-seed without it becoming invasive.

Positive e_e_e On Oct 5, 2010, e_e_e from Atlantic City, NJ wrote:

ive grown cosmos the past 3 summers.
i originally had them in a pack of assorted wildflowers. i didnt know what they were at first but they each grew to 8-9 ft and were beautiful so i saved the seeds from the flowers for the next spring.
i had to look them up for info but contrary to what i read about their size, my cosmos have varied greatly in height.
i have some now that are around 5-6 ft high and another 2 around 9 ft. and i have one plant right now thats over 10 ft and today is the first day it bloomed a flower. (oct. 5) ive been waiting all summer for it as my other cosmos have been flowering all summer. dont know why this big one has taken so long.
i grow them in full sun and they get water every day along with an occasional drink of miracle grow.
so far ive had 2 colors, pink and white.
they are beautiful willowy plants and im constantly finding more and more places to grow them.

Positive Opoetree On Jun 9, 2007, Opoetree from Oak View, CA wrote:

I have grown cosmos for years....the flower is my husband's and son's birthday month flower. I also notice them all over my little town in the Ojai Valley. For some reason, they are blooming earlier this year. Generally they bloom in October (when they are supposed to, because they are the flower for the month of October!). Easy to grow, I even have some popping up from seed in my cactus pots. Seems like the purple variety is the most durable and prolific. Like the foliage as well...feathery. Easy to grow, friendly to have around....not demanding in any way.

Positive lemmons75 On Jul 26, 2006, lemmons75 from Rock Hill, SC wrote:

This plant is unlike anything I have ever come across.It was giving to me by a neighbor in a seed pack (with other seeds).It first came up it was 2 ft tall but no flowers.I transplanted it twice and now it sets alone in a 5 gal. bucket with awsome pink flowers.I'm 6ft tall and it is a bit taller than me.I have ended up tieing it up to keep it from falling over.This is one plant that I will plant next year and give some seeds away.

Positive Gabrielle On May 22, 2006, Gabrielle from (Zone 5a) wrote:

They are very pretty flowers, but need pinching back or staking early on to prevent flopping.

Positive Suze_ On May 2, 2006, Suze_ from (Zone 7b) wrote:

What can I say, but that I just love cosmos. C. bip regularly gets to 4-6 ft or more in my garden, though.

Positive tiffanya On Aug 26, 2005, tiffanya from Sumner, WA (Zone 8a) wrote:

Cosmos are very easy to grow. I sow along the fenceline each spring. In 2004, they grew very tall (most measured at 9 feet high), mostly due to a combination of steer manure in the garden and the neighbor's active sprinklers sharing water along the fenceline. It was literally a jungle of cosmos. I kept dead-heading them, and they bloomed pretty much from July into October.

I especially love the star-shape pistil/stamen area as the pollen is released...very pretty. The dragonflies also appear to be attracted to the color...?

(Western Washington State)

Positive PurplePansies On Jun 24, 2005, PurplePansies from Deal, NJ (Zone 7a) wrote:

I believe cosmos to be a "must have" for every garden. They are a beautiful flower.... now with so many fun varieties .... and so easy to grow! Simply scatter seeds in the garden and they will grow like mad! That being said they are also not harmfully invasive. Birds also love the seeds. Many of its colors blend nicely with other colors in the garden. Attractive divided foliage. A winner all around. Try it you will not be dissapointed! :)

Positive angele On May 5, 2005, angele wrote:

Such great performance makes it a favorite in my SW garden.

Positive LilyLover_UT On Jan 16, 2005, LilyLover_UT from Ogden, UT (Zone 5b) wrote:

Cosmos are easy to grow from seed sown directly in the garden in mid to late spring. They also self-sow vigorously, and they attract beneficial insects.

Positive lupinelover On Jul 29, 2002, lupinelover from Grove City, OH (Zone 6a) wrote:

Best grown in poor soil; rich feeding leads to very big branches with poor flowering which tend to be floppy. Deadheading prolongs flowering.

Neutral lantana On Jan 4, 2001, lantana from (Zone 7a) wrote:

Grows in Heat Zones 12-1.

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

This species of cosmos is an annual, grows 5' to 6' high. Flowers in summer and autumn in various colors of pink, red, white and purple. May need staking. Best cultivated in sun, with average soil. Not very frost hardy.


This plant has been said to grow in the following regions:

Auburn, Alabama
Dothan, Alabama
Peoria, Arizona
Little Rock, Arkansas
Concord, California
Magalia, California
Merced, California
Murrieta, California
Oak View, California
San Jose, California
Stockton, California
New Haven, Connecticut
Lewes, Delaware
Seaford, Delaware
Clermont, Florida
Gainesville, Florida
Keystone Heights, Florida
Lake City, Florida
Vero Beach, Florida
Braselton, Georgia
Douglasville, Georgia
Hawkinsville, Georgia
Lawrenceville, Georgia
Stone Mountain, Georgia
Kailua, Hawaii
Lewiston, Idaho
Itasca, Illinois
Nilwood, Illinois
Peoria, Illinois
Washington, Illinois
Columbus, Indiana
Norwalk, Iowa
Lansing, Kansas
Hebron, Kentucky
North Billerica, Massachusetts
Ann Arbor, Michigan
Webberville, Michigan
Ypsilanti, Michigan
Deer River, Minnesota
Florence, Mississippi
Berlin, New Hampshire
Greenville, New Hampshire
Munsonville, New Hampshire
Atlantic City, New Jersey
Albuquerque, New Mexico
Fletcher, North Carolina
Massillon, Ohio
Reynoldsburg, Ohio
Springfield, Ohio
Ashland, Oregon
Brookhaven, Pennsylvania
Scranton, Pennsylvania
Rock Hill, South Carolina
Greeneville, Tennessee
Abilene, Texas
Austin, Texas
Broaddus, Texas
Fort Worth, Texas
Houston, Texas
Lewisville, Texas
San Antonio, Texas
Santa Fe, Texas
Tremonton, Utah
Danville, Virginia
Kalama, Washington
Olympia, Washington
Spokane, Washington
Black Earth, Wisconsin
Madison, Wisconsin

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