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)
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Foliage Color:


Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Water Requirements:

Drought-tolerant; suitable for xeriscaping

Average Water Needs; Water regularly; do not overwater

Where to Grow:

Unknown - Tell us


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:

Unknown - Tell us

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

Self-sows freely; deadhead if you do not want volunteer seedlings next season

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds

Properly cleaned, seed can be successfully stored


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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Gardeners' Notes:


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

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


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. ... read more


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.


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.


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.


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.


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)


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! :)


On May 5, 2005, angele wrote:

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


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.


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.


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

Grows in Heat Zones 12-1.


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.