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Western Wetland Flora

Field Office Guide to Plant Species

Small-flower Sumpweed
Iva axillaris Pursh

JPG -- Species Photo JPG -- Distribution Map

Family: Composite (Compositae)
Flowering: May-September
Field Marks: The genus Iva consists of species with inconspicuous heads comprised only of greenish white, short, tubular flowers. The bracts are united at the base to form a cup.
Habitat: Salt marshes, alkaline flats.
Habit: Perennial herb with creeping rhizomes.
Stems: Upright, or lying flat before becoming upright, branched or unbranched, up to 2 feet tall, smooth or hairy.
Leaves: Lower leaves opposite, upper leaves alternate, all simple, obovate to oblanceolate, up to 2 inches long, up to 3/4 inch wide, rounded or somewhat pointed at the tip, tapering to the nearly sessile or sessile base, without teeth, 3-veined
Flowers: Several crowded into nodding heads, with a single head in the axils of the leaves, each head up to 1/4 inch across, consisting only of greenish white tubular flowers: bracts subtending each head united to form a cup.
Sepals: 0.
Petals: 5, greenish white, united to form a short, tubular flower.
Stamens: 5.
Pistils: Ovary inferior.
Fruits: Achenes obovoid, smooth although sometimes glandular, up to 1/8 inch long.
Notes: The outer flowers of the disk are only female, while the inner flowers have both stamens and pistils.

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U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/plants/florawe/species/7/ivaaxil.htm
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Page Last Modified: Saturday, 02-Feb-2013 06:27:14 EST
Menlo Park, CA [caww54]