Aquatic Plant Identification Manual for Washington's Freshwater Plants
|Species:||Lobelia dortmanna L., water lobelia|
This perennial plant can be identified by its low growing tufts of cylindrical or somewhat flattened tubular leaves and its erect, unbranched flower-stalk. The leaves are somewhat grass-like and usually whitish at the base. Many white roots anchor it to firm sediment in shallow sandy areas of lakes and ponds. In summer, look for the small pale blue or white snapdragon-like flowers waving above the water surface.
Leaf: The leaves originate from a central base. They are narrow, long (to 8 cm), often curved, and are made of 2 side-by-side hollow tubes that are round or slightly flattened in cross-section. A few tiny, thin, alternate leaves are sometimes present along the flower stem.
Stem: The hollow, smooth, mostly unbranched stem usually rises above water surface. It can grow to 2 m tall and supports flowers and sometimes tiny leaves or bracts, but is often a bare stalk after the flowers and fruits drop.
Flower: White or pale blue flowers (1-2 cm long) are attached individually by short stalks to the stem. The flowers have 5 sepals and the base of the 5 petals is fused into a tube. The 2 shorter upper petals fold up. Several well-spaced flowers grow from each stem.
Fruit: The capsule is 5-10 mm long and 3-5 mm wide. Tiny seeds (less than 1 mm) have a distinctive square base.
Root: Fibrous, whitish.
Propagation: Seed; vegetative buds at the base of old flower stems.
Importance of plant: Listed as a threatened plant species in Washington.
Distribution: Northern North America, northwestern Europe. In Washington found west of the Cascade Mountains.
Habitat: Grows on hard, firm sandy or gravely sediments in shallow to moderately deep slightly acidic still waters. Produces flowers in water to 2 m deep.
May be confused with: Distinctive when flowering. Without the flower stalk it looks similar to low growing grass-like aquatic plants such as quillwort (Isoetes lacustris), mudwort (Limosella acaulis), flowering quillwort (Lilaea scilloides), and lilaeopsis (Lilaeopsis occidentalis). Look for slightly flattened, fleshy, curved leaves. Do not harm these rare plants.
Photographs: Closeup of young Lobelia dortmanna plants
Line Drawings: None available