Sparganium angustifolium (Narrow-leaf Bur-reed)

Plant Info
Also known as: Floating Bur-reed
Genus:Sparganium
Family:Sparganiaceae (Bur-reed)
Life cycle:perennial
Origin:native
Habitat:sun; shallow to 5+ feet deep water; lakes, ponds, rivers
Bloom season:July - August
Plant height:12 to 40 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
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: round

[photo of flower clusters] Round flower heads in a spike-like arrangement at the top of the stem, with separate male and female flower heads on the same plant (monoecious).

[photo of male flower heads] At the tip of the stem are 2 to 4 stalkless male flower heads, usually crowded and appearing as a single elongated head, each covered in dozens of petal-less flowers with yellow-tipped white stamens. Male flower heads turn brown, wither and drop off after pollen release, the naked part of the stem usually persisting for a time but eventually also withering away.

[photo of supra-auxillary female flower heads] Two to 5 female flower heads sit below the males, are slightly larger than the males, and are single in the axils of leaf-like bracts, the upper head(s) stalkless, the lowest head(s) stalked with the stalk at least partially fused to the stem so the head looks attached to the stem above the axil (known as supra-auxillary). Individual flowers have a single style at the tip of a green ovary and are surrounded by scale-like tepals (petals with similar sepals) that lack a darker spot near the tip.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of leaves] Leaves are alternate and basal, all floating on the surface, linear, to 4 feet long, to ¼ inch (2 to 6 mm) wide, hairless, toothless, flat on the upper surface, flat to convex on the lower.

[photo of leaf cross-sections and veins] Surfaces are green, the lower surface with green parallel veins and no keel. Leaves become more translucent below the water's surface. Stems are erect, green and smooth. Flowering stems rise slightly above the surface of the water.

Fruit: Fruit type: seed without plume

[photo of developing fruit] Female flower heads form densely packed seed heads that expand up to about 1 inch (to 30 mm) diameter, the plump, spiky head maturing from light green to reddish-brown.

[photo of maturing fruit] Fruit is elliptic to somewhat fiddle-shaped, the body 3 to 7 mm (to ~¼ inch) long, tapering to a short stalk-like base (stipe), the tip more abruptly tapering to a slender, straight beak shorter than the body.

Notes:

Narrow-leaf Bur-reed is an occasional to common aquatic in the northeastern quadrant of Minnesota, found in the quiet waters of clear lakes, ponds and slow-moving rivers, often in less than 3 feet of water, sometimes deeper. We have often seen it in diffuse colonies with the slender floating leaves all pointing in the same direction, almost like a parade—it's quite lovely.

There are 4 Sparganium species in Minnesota that have long, ribbon-like floating leaves; S. angustifolium is distinguished by widest leaves 3 to 6 mm wide, unbranched flower clusters, usually 2 to 4 male flower heads crowded at the tip of the stem, 2 to 5 female heads, single from leaf-like bracts, the upper female heads stalkless and the lower stalked but appearing to arise from a point above the bract axil (supra-auxillary), fruiting heads up to ~1 inch (3 cm) diameter, fruit with straight beaks shorter than the body. It can form colonies that may have few flowering stems.

Of the Sparganium species with floating leaves, Floating Bur-reed (Sparganium fluctuans) may be most similar but has widest leaves 6 to 10 mm, branched flower clusters, and fruit is distinctly red with strongly curved beaks. Small Bur-reed (Sparganium natans) is a smaller plant, under 2 feet tall, with a single male head at the stem tip and no supra-auxillary female heads. Unbranched Bur-reed (Sparganium emersum) sometimes has floating leaves but more often has stiffer, erect leaves that are keeled on the back and triangular in cross-section. American Eelgrass (Vallisneria americana) also has long, ribbon-like leaves, but with a very different vein pattern.

Please visit our sponsors

  • Wild Ones Twin Cities Chapter

Where to buy native seed and plants ↓

Map of native plant purveyors in the upper midwest

  • Shop for native seeds and plants at PrairieMoon.com!
  • Shooting Star Native Seeds - Native Prairie Grass and Wildflower Seeds
  • Morning Sky Greenery - Native Prairie Plants
  • Minnesota Native Landscapes - Your Ecological Problem Solvers
  • Natural Shore Technologies - Using science to improve land and water

More photos

Photos by K. Chayka taken in Aitkin and Cook counties. Photos by Peter M. Dziuk taken in Carlton, Cook and Itasca counties.

Comments

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

Post a comment

Note: All comments are moderated before posting to keep the riff-raff out. An email address is required, but will not be posted—it will only be used for information exchange between the 2 of us (if needed) and will never be given to a 3rd party without your express permission.

For info on subjects other than plant identification (gardening, invasive species control, edible plants, etc.), please check the links and invasive species pages for additional resources.



(required)




Note: Comments or information about plants outside of Minnesota and neighboring states may not be posted because Id like to keep the focus of this web site centered on Minnesota. Thanks for your understanding.