Giant Ragweed (Ambrosia trifida)

Common names:
Give a thumbs up Giant Ragweed
Give a thumbs up Palmate Ragweed
Give a thumbs up Great Ragweed

Botanical names:
Ambrosia trifida Accepted
Ambrosia trifida var. trifida Synonym

General Plant Information (Edit)
Plant Habit: Herb/Forb
Life cycle: Annual
Sun Requirements: Full Sun
Water Preferences: Mesic
Plant Height: up to 15 feet
Flowers: Inconspicuous
Flower Color: Green
Other: green/white
Flower Time: Fall
Pollinators: Wind

plant growing along the road in July

Photo gallery:

This plant is tagged in:

Posted by jmorth (central Illinois) on Oct 30, 2011 2:33 PM

Pollen from this plant is a major source of hay fever.
Seeds from this plant have been discovered in several archaeological sites, prompting the idea it may have been cultivated as a food source.
Likes moist soils in low woods, along floodplains, steams, disturbed sites, roadsides, and railroad right of ways.

[ Reply to this comment | Give a thumbs up ]

Posted by gardengus (Indiana Zone 5b) on Oct 14, 2013 9:52 AM

As a kid we knew these as Horseweeds. They are eaten in the pasture area by horses, goats, and cows. In areas where they are allowed to go to seed, they seem to be loved by finches of all colors.

This weed is an annual from the aster family. It can grow up to 16 feet, mostly where it has ample water.

Native to North America, found in almost all states, and used by Native Americans.

[ Reply to this comment | Give a thumbs up ]

Posted by Chillybean (Iowa - Zone 5a) on Sep 28, 2015 12:14 PM

No one in our family has ragweed allergies, so I can view this plant more favorably than those who suffer. In restoration settings, it is considered a pioneer plant. An area becomes disturbed and the Giant Ragweed will readily fill in empty spaces. As more desirable plants starting popping up, this one will decrease. This plant prefers wetter areas, so in years of drought it will not thrive.

It does not attract many pollinating insects because this is wind pollinated. The larvae of several moths consume the leaves, stems, flowers and seeds. Because of its hard shell, the birds do not readily consume the seeds. Cattle and deer will graze on the foliage.

This plant is truly a giant, which makes it a fun place for the children to hide and run around in. The only time it wasn't so much fun was when they were startled by a family of Pheasants that also found it a nice hiding spot.

This fall I had my first trek through all the ragweed. Oh, it was amazing! I felt like I was walking through a forest. I found the developing seed heads quite fascinating. Birds may not eat the seeds, but they do like foraging for insects among the stems and leaves. I have seen far fewer birds at my feeders... well, this is where they are!

[ Reply to this comment | Give a thumbs up ]

Discussion Threads about this plant
Thread Title Last Reply Replies
Giant Ragweed - Texas style? by greene Jun 15, 2018 6:02 PM 2
What could this be? by wildflowers Mar 30, 2018 9:04 AM 10
What kind of plant is this? by alexfoc Aug 10, 2016 8:06 PM 8
Tall, lobed leave monster. by threegardeners Jul 29, 2016 5:05 PM 2
This is growing next to my peppers by Brumpy Jun 18, 2016 7:11 PM 8
Trying to idenitify a strange plant that grew at my old house. by corythomas42 Jun 3, 2016 5:35 PM 14
Any idea what this is? by Frillylily May 26, 2016 7:35 PM 7
Flower ? by Anderwood Jun 5, 2014 6:47 AM 2
Unknown volunteer by wildflowers Nov 5, 2013 10:22 AM 28
What's this weed? by piksihk Mar 26, 2013 8:39 PM 7

« Add a new plant to the database

« The Plants Database Front Page

Today's site banner is by Marilyn and is called "Winter Aconite"