PlantFiles: Giant Ragweed, Great Ragweed, Palmate Ragweed
Ambrosia trifida

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.

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.

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.

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.

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.

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.

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.