Ambrosia artemisiifolia (Common Ragweed)

Plant Info
Also known as: Annual Ragweed
Genus:Ambrosia
Family:Asteraceae (Aster)
Life cycle:annual
Origin:native
Status:
  • Weedy
Habitat:part shade, sun; disturbed soil, fields, along roads, waste areas, open woods
Bloom season:July - September
Plant height:1 to 3 feet
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: indistinct Cluster type: raceme Cluster type: spike

[photo of flowers] Slender spike-like racemes, sometimes branched, from 1 to 6 inches long at the tip of the central stem and branches. Male (staminate) flowers are yellow to greenish, tiny, hanging down on short stalks, petal-less and bead-like. Female flowers are indistinct, tucked away in clusters with short leafy bracts at the base of the cluster, along the stem or in the axil. Clusters are initially densely packed, spreading out as the plant matures.

Leaves and stem: Leaf attachment: alternate Leaf attachment: opposite Leaf type: lobed Leaf type: simple

[photo of leaves] Leaves are thin, fern-like, deeply lobed with many of the side lobes deeply lobed again (1-2 pinnate), generally egg-shaped in outline, up to 6 inches long and 4 inches wide near the base, hairy but may become smooth with age. The lower leaves are oppositely attached, the upper are alternate. The stem is typically heavily branched and variably covered with soft, erect, white hairs and often has a purple tint.

Notes:

Common Ragweed is an early pioneer species of disturbed soils, has been introduced worldwide and is now a common weed in both agricultural and urban sites. With high population densities and prolific production of highly allergenic pollen, it is a major contributor to the agony of hayfever suffers around the globe. It can become quite bushy and grow in clumps or colonies. Most similar is the perennial Western Ragweed (Ambrosia psilostachya), which is less heavily branched, has leaves less finely divided, and has fibrous rhizomes where Common Ragweed is taprooted.

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More photos

Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka County.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Jean - Minneapolis
on: 2014-09-13 20:06:49

In my back yard in Longfellow neighborhood. I thought it was cute, so I drew it and then searched for an ID.

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