Montana Field Guide

Stems 5–40 cm. Leaves 10–35 mm long; the dilated base 2–3 mm wide. Female flowers 2–5 mm long. Achenes ca. 3 mm long; seeds smooth, shiny, sometimes minutely spotted (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Slender Naiad - Najas flexilis, Native
*Leaves: 10–35 mm long with a dilated base that is 2–3 mm wide. From about their mid-section, leaves have a long taper that terminates in a long slender point. Prickles lacking.
*Seeds: Smooth, shiny, and sometimes minutely spotted.

Guadalupe Water-nymph - Najas guadalupensis, SOC
*Leaves: 5-15 mm long with minutely toothed margins. Ribbon-like with short tapering tips and expanded bases. Additional leaves are often found in the axils. Prickles lacking.
*Seeds: Dull and coarsely pitted, with a honeycomb surface.

Spiny Naiad – Najas marina, Exotic
*Leaves: Coarsely serrated margins with 8 to 13 teeth on each side of the blade. Prickles can be found on the abaxial (lower) surface of the blade.
*Seeds: Ovoid, reddish brown, and pitted with areoles (outer two coatings of the testa) irregularly arranged, not in distinctive rows or not ladder-like. Seeds are longer than broad with the end walls slightly raised.

Brittleleaf Naiad - Najas minor, NOT DOCUMENTED IN MONTANA
*Leaves: At maturity, blades recurve and become stiff with age. Prickles lacking.
*Seeds: Broader than long and with areoles arranged in longitudinal rows – like the rungs of a ladder.

TAXONOMY
The Najas genus is sometimes placed in the Family Hydrocharitaceae, also known as the Waterweed or Frog’s-bit Family.

Usually shallow, often alkaline water of lakes, sloughs; valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).