Montana Field Guide

Leaves 5–12 × 1.5–2.5 mm, minutely serrate, narrowly lanceolate and opposite below to more linear and 3-whorled above. Male flowers: spathe to 15 mm long, inflated above; sepals 3–5 mm long; petals 4–5 mm long; stamens 7 to 9. Female flowers: spathe 1–2 cm long, not inflated; sepals ca. 2 mm long, purplish; petals 2–3 mm long. Capsule 5–6 mm long (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

The native Elodea canadensis has dark green leaves that are often speckled with large dark cells (DiTomaso and Healy 2003). Middle and upper leaves are opposite or 3-whorled and those below the growing tips often curve slightly downward (DiTomaso and Healy 2003). Leaves are often relatively longer and narrower in comparison to exotic species. The mid-vein of each leaf is smooth on its underside (DiTomaso and Healy 2003). Roots are more wiry when compared to Hydrilla verticillata and Egeria densa.

The exotic species of Hydrilla verticillata also have whorled leaves, but in groups of 3-12 that are 6-20 mm long and 1-4 mm wide (DiTomaso and Healy 2003). Leaves below the growing tips are often curved downward (DiTomaso and Healy 2003). The mid-vein of each leaf is smooth or minutely toothed on its underside (DiTomaso and Healy 2003).

The exotic species of Egeria densa also has whorled leaves, but in groups of 3-8 that are 15-40 mm long and 2-5 mm wide. The mid-vein of each leaf is smooth or minutely toothed on its underside (DiTomaso and Healy 2003).

Shallow to deep water of lakes, ponds, sloughs, slow streams; valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Axillary buds occur at nodes, at about 10 cm intervals (DiTomaso and Healy 2003).