Swamp Smartweed

Plant Info

Also known as:	Longroot Smartweed, Water Knotweed
Scientific name:	Polygonum amphibium
Family:	Buckwheat (Polygonaceae)
Life cycle:	perennial
Origin:	native
Habitat:	sun or part shade; moist soil, ditches, along shores, shallow water
Bloom season:	summer
Plant height:	1 to 3 feet
USDA PLANTS database:	Minnesota county distribution map
Spotted in Ramsey County at:	Long Lake Regional Park Rice Creek Trail Corridor Vadnais/Snail Lake Regional Park

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Detailed Information

Flower:

Spike clusters 2 to 4-inches long; individual flowers are 1/8-inch across, deep pink with 5 petal-like sepals and long stamen. Each plant has 1 or 2 spikes.

Leaves and stem:

Leaves are up to 8 inches long and 3 inches wide with smooth but wavy edges tapering to a point at the tip, and may have fine hairs. A brown paper-like sheath is attached to the stem at the base of each leaf (not a great picture of this, but at least you should see the color difference). Leaves are alternately attached up the stem.

Notes:

Swamp Smartweed is a variable species, apparently with both terrestrial and aquatic versions. The leaves of the aquatic form usually aren't as wavy.

More photos

• a small patch of Swamp Smartweed
• aquatic form of Swamp Smartweed, in a shallow creek

All photos taken at Long Lake Regional Park, New Brighton, MN, July-August 2006.

Comments

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

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Please: Do not ask about where to buy seed or other gardening questions, are plants edible, etc. I am not a horticulturist or botanist, just an enthusiastic hobbyist so I probably don't know the answer. Please check the links page for additional resources. -thanks much

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