Submersed Plants

 
Species: Subularia aquatica L., awlwort
Family: Brassicaceae

This small, rather uncommon, underwater herb appears as a tuft of quill-like leaves with a leafless flower stalk growing 2-10 cm tall. The small, white, 4-petaled flowers appear in a loose cluster along the ends of the stalks. The plant is found in shallow water in clear, cold lakes and slow streams, often on sandy or gravelly sediments. Awlwort is a member of the mustard family and produces the oblong seedpods that are characteristic of that family. It is usually an annual plant, although it may overwinter if completely submersed.

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Leaf: Narrow leaves (1-5 cm long) are wider at the base and taper to a pointed tip. The leaves are round in cross-section with all the leaves emerging from the plant base.

Stem: Short, thick, underground corm between the leaves and roots.

Flower: 2 to 8 small (1 mm long) flowers are arranged in a loose cluster at the end of flower stalks. Each flower has 4 sepals and 4 white petals. The flower stalks are smooth and erect to 12 cm tall and may have a few green leaf-like bracts. If submersed, the flowers self-pollinate while remaining closed. Flowers open if above the water surface. Blooms June through August. 

Fruit: Inflated, oblong, ribbed pods are 2-3 mm long with each pod containing several seeds.

Root: White, fibrous roots. Lacks rhizomes.

Propagation: By seeds. 

Importance of plant: Provides habitat for small animals, stabilizes shorelines, and is occasionally cultivated for aquaria.

Distribution: Across northern North America and also Eurasia, although Eurasian plants are often considered a different variety.

Habitat: Submerged in streams, lake shorelines, and shallow ponds. Usually in gravelly substrates; sometimes exposed as water levels drop.

May be confused with: Many other small tufted plants such as: spikerushes (Eleocharis spp.) which have solitary cone-like flower clusters that usually rise above the water surface, and do not produce inflated pods; water lobelia (Lobelia dortmanna), which has similar rosettes of leaves, but the leaves are hollow and less pointed; quillwort (Isoetes lacustrus), which has a distinctive, widened leaf base; mat mudwort (Limosella acaulis) which usually has flattened leaf tips and distinctive root growth; lilaeopsis (Lilaeopsis occidentalis), which has rhizomes; and flowering quillwort (Lilaea scilloides) which has longer leaves and flowers lacking distinct petals and sepals. 

Photographs: Subularia aquatica

Line Drawings: None available 


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