Giant Ragweed, Great Ragweed, Palmate Ragweed

Ambrosia trifida

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Ambrosia (am-BRO-zhuh) (Info)
Species: trifida (TRY-fee-duh) (Info)
Synonym:Ambrosia trifida var. trifida



Foliage Color:

Unknown - Tell us

Bloom Characteristics:

Unknown - Tell us

Water Requirements:

Drought-tolerant; suitable for xeriscaping

Average Water Needs; Water regularly; do not overwater

Where to Grow:

Unknown - Tell us


6-8 ft. (1.8-2.4 m)

8-10 ft. (2.4-3 m)

10-12 ft. (3-3.6 m)

12-15 ft. (3.6-4.7 m)


24-36 in. (60-90 cm)


Not Applicable

Sun Exposure:

Full Sun


Handling plant may cause skin irritation or allergic reaction

Pollen may cause allergic reaction

Bloom Color:



Bloom Time:

Mid Summer

Late Summer/Early Fall



Other details:

May be a noxious weed or invasive

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:

From seed; direct sow outdoors in fall

From seed; stratify if sowing indoors

Scarify seed before sowing

Seed Collecting:

Bag seedheads to capture ripening seed

Properly cleaned, seed can be successfully stored


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

Brunswick, Georgia

Champaign, Illinois

Glen Ellyn, Illinois

Indianapolis, Indiana

Oakland City, Indiana

Valparaiso, Indiana

Yale, Iowa

Benton, Kentucky

Hebron, Kentucky

Boonsboro, Maryland

Gregory, Michigan

Highland, Michigan

University Center, Michigan

Minneapolis, Minnesota

Belton, Missouri

Cole Camp, Missouri

Piedmont, Missouri

Saint Robert, Missouri

Beatrice, Nebraska

Doniphan, Nebraska

Kearney, Nebraska

Hyde Park, New York

Union Springs, New York

Youngstown, Ohio

Edmond, Oklahoma

Jay, Oklahoma

Bradford, Pennsylvania

Downingtown, Pennsylvania

Arlington, Texas

Austin, Texas (2 reports)

Boerne, Texas

Cleburne, Texas

Dallas, Texas

Frisco, Texas

Garland, Texas

Port Neches, Texas

San Antonio, Texas

Santa Fe, Texas

Radford, Virginia

Falling Waters, West Virginia

Appleton, Wisconsin

Janesville, Wisconsin

show all

Gardeners' Notes:


On Aug 22, 2015, Rickwebb from Downingtown, PA wrote:

This is a very common native plant in fields of the Midwestern and Eastern US that is considered by many as a noxious weed because its pollen causes so much allergy among so many people in late summer to mid-autumn. (It is not any Goldenrod that does this as its heavy pollen is spread by bees and other pollinators.) I am one who gets some allergy from this and Common Ragweed. It has a certain non-flashy beauty when growing in groups, not individual plants so much. It is native and has a place in the US, but I don't want it to be too common.


On Jun 1, 2013, plant_it from Valparaiso, IN wrote:

It's a native plant (native to the U.S. anyway), so that's a positive. Other than that, I can't see that it has that much going for it. The leaves and seeds aren't particularly liked by wildlife, so I certainly wouldn't add this to the wildlife garden. And it's an allergy sufferer's worst nightmare.
This huge plant is probably an allergy sufferer's worst nightmare.

"It has some ecological value to various moths, but otherwise is less important than Ambrosia artemesiifolia (Common Ragweed). Giant Ragweed can be distinguished from other Ambrosia spp. (Ragweeds) by its palmately lobed leaves; other Ragweeds have leaves that are pinnatifid or bipinnatifid. The name of this genus of plants refers to ambrosia, "the food of the gods... read more


On Feb 19, 2008, Malus2006 from Coon Rapids, MN (Zone 4a) wrote:

Giant ragweed are more oftenly seen in gardens than common ragweed but in other locations such as roadside common ragweed is far the most often. It is easily identify by its strongly three lobed leaves that look kind like sassafras but is not woody. It is also common only in certain area like when construction workers clear out all the vegetation on the roadside for a certain period of years before grasses and other agressive species reduce the numbers - it will persists in certain locations. Giant ragweed is easy to control - it is the rain of seeds that comes in from nearby locations that is the main headache for this weed.


On Dec 16, 2004, Pyrola5 from Bradford, PA (Zone 5a) wrote:

Giant ragweed came up in my flower bed one year,I didn't know what it was so I let it grow. It was GIANT, well over my head. I sent pictures to the county agent. He told me what it was and I dug it out and got rid of it. It never returned. I live in NW PA, so it definitely grows here. My daughter is allergic to ragweed.


On Dec 15, 2004, BotanyDave from Norman, OK (Zone 7a) wrote:

A beautiful weed with an interesting and easily controlled growth pattern. The leaves may be unlobed, or multiple-lobed (although the most common are 3, 5, or 7). Plants are very difficult to transplant, but it can be done if water is used constantly. Seeds need to be outside during winter in order to germinate in the spring- treating in the house is possible but difficult (or they could be treated with various chemicals). Plants in partial shade and damp soil do very well. Mature plants are easily removed with a saw.


On Sep 1, 2004, trois from Santa Fe, TX (Zone 9b) wrote:

The plant is attractive. The alergy reaction is not. There is no way to control this plant here without destroying all the native vegitation. We will tolerate it.


On Aug 30, 2004, melody from Benton, KY (Zone 7a) wrote:

A common pest weed in these parts. It produces so many seeds that it's place is assured in the ecosystem.

The pollen causes allergic reactions to many people and some folks can get quite sick.

On the up side, the oil rich seeds are a food source to songbirds and other wildlife.


On Jan 31, 2003, Muckdiver from Saint Louis, MO wrote:

I found a way to eliminate the ragweed by cutting the stem near the base, just before it started to bloom in the fall.
A weed-whacker is a good way to do this. Note that seeds remain in the ground and will germinate if the soil is tilled; the seedlings can be pulled if this happens.


On Jan 25, 2003, lupinelover from Grove City, OH (Zone 6a) wrote:

Although the seedlings are fairly attractive, this plant should be pulled as soon as it is identified. It grows so large that it is very difficult to dislodge when it is beyond seedling size.