Giant Ragweed – Identification

Q: I have a very strange plant that has apparently killed or is stunting kudzu on my vacant lot.

This is not a joke.

The kudzu began healthy as usual this year, but was suddenly—and I mean suddenly—overtaken and stunted down to tiny plants around the middle of July. What has taken its place is a very tall, stalky and dense plant with seed bearing appendages that point upwards in groups of three or four. These plants grow close together and get over 9 feet tall. But these plants have so suddenly supplanted the kudzu all around my house that I am worrying about exactly what they are.


A homespun “horticulturist” told me that the sudden appearance of this plant and its phenomenal proliferation since July was due to a cloud of radioactivity that drifted over Atlanta from the accident in Japan.

I am not a conspiracy theorist or a nutcase. I have been in GA since 1983, and I have never seen a plant take over so quickly. Also, I have never seen anything stunt the kudzu to this degree. I have NEVER seen something take over so quickly.

A: How well I remember as a kid blazing trails through patches of this tall weed, which had grown thickly in an unused cow feedlot on our family farm.

It’s giant ragweed, Ambrosia trifida. The stalks grew well above my head when I was ten.

You are right….it’s so prolific that it can fight kudzu to a standstill.

Although grain and soybean farmers hate it, one author says it is great habitat for quail and other birds.

see The Irony of Giant Ragweed

Since it comes up from seed, regularly knocking it down will interrupt its blooming and prolific seed production. Any young boy with a stick sword is perfect for this project.

Failing that, a non-selective weed killer like glyphosate (Roundup, etc) would kill it, particularly when young.

On the other hand, I definitely have warm feelings toward a plant that can fight kudzu to a standstill!

giant ragweed

giant ragweed

giant ragweed

giant ragweed

giant ragweed

giant ragweed

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