Juncus bufonius (Toad Rush)

Plant Info
Also known as:
Genus:Juncus
Family:Juncaceae (Rush)
Life cycle:annual
Origin:native
Habitat:sun; moist to wet; shores, banks, wet meadows, marsh edges, wet ditches
Fruiting season:June - October
Plant height:2 to 12 inches
Wetland Indicator Status:GP: OBL MW: FACW NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 6-petals Cluster type: panicle

[photo of cluster branches] Open, branching cluster about half the total height of the plant, the branches ascending to widely spreading. Flowers are mostly single at the nodes, sometimes in heads of 2 to 4, usually all on one side of a branch, with a small, brown, papery, scale-like bract at the base of a flower. At the branch node are a pair of bracts which may be leaf-like or scale-like.

[close-up of branch] Flowers are short-stalked and have 6 tepals (petals and similar sepals) in 2 layers, the outer 3 to 6 mm long, the inner slightly shorter, both narrowly lance-shaped, tapering to a sharply pointed tip, green with translucent white edging. Flowers have a 3-parted style and 6 stamens, the anthers (tips) as long as or shorter than the filament (stalk). Sometimes self-pollinating flowers that do not open (cleistogamous flowers) are formed.

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

[photo of sheath, lacking auricle] A flowering stem has 1 or 2 alternate leaves along the stem and usually a few basal leaves, sometimes more. Leaves are ½ to 4 inches long, up to 1.1mm wide, convex on the underside and flat or channeled on the upper. The sheath is open at the front. The tip of the sheath is rounded but lacks any lobes (auricles) that extend above the leaf base.

[photo of plant base] Basal sheaths are typically red to purplish. Stems are round in cross-section, smooth, erect to prostrate, usually unbranched except in the flower clusters, usually multiple from the base and forming loose to dense clumps.

Fruit: Fruit type: capsule/pod

[photo of mature fruit] Fruit is a single-chambered capsule, 3 to 4 mm long, chestnut to reddish-brown, oval with a rounded tip and about as long as or shorter than the persistent tepals. Seeds are oval-elliptic, .3 to .6mm long, amber colored with a network of minute ridges across the surface.

Notes:

Juncus bufonius is occasional in soil that is subject to seasonal fluctuations in water levels, often sandy or gravelly soil or the compacted soils of ATV trails and foot paths. It is a fairly distinctive Juncus, distinguished by the short stature (rarely more than 8 inches tall, usually less), clump-forming habit, open, many-branched cluster about half the total height of the plant, flowers and fruits mostly on one side of a branch, and sheaths that may be rounded at the tip but lack a distinct auricle. This lack of auricle separates it from almost all other Juncus species in Minnesota. Somewhat similar is Juncus pelocarpus, a colony forming perennial that has distinct auricles on its sheaths and tepals are less than 3mm long, where J. bufonius tepals are 3 to 6mm long. A variable species, some references distinguish multiple varieties of J. bufonius, but these are not recognized in Minnesota.

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More photos

Photos courtesy Peter M. Dziuk taken in Cook and Washington counties.

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