Lesser Duckweed - Lemna minor
Common Duckweed, Water Lentil
MNPS Threat Rank
Montana species of the Duckweed Family are all small, perennial, free-floating, aquatic herbs distinguished by their veins and roots. Veins are best observed using a 10x magnification and back-lighting (Giblin et al. [eds.] 2018) or by placing on a transparent slide (Landolt in
FNA 2000). Landolt in
FNA (2000) provides some techniques to analyze anatomy. In this family the term "leaf" cannot be used because a leaf consists of a stem (petiole) and a blade (Landolt in
FNA 2000). Instead the term "frond" is used. Be aware that species can grow in the same place naturally. Lemna
- Duckweed, native
* Fronds: Green above and mostly below.
* Root: 1 per frond, sometimes absent.
* Veins: 1-3 per frond.Spirodela
- Duck-meal, native
* Fronds: Green above and usually purplish below.
* Roots: 2 or more per frond
* Veins: 3 or more per frond.Wolffia
- Water-meal, native
* Fronds: Green to brown.
* Root: 0; absent.
* Veins: 0; absent.Lesser Duckweed
- Lemna minor
*Compare to Lemna turionifera
*Fronds: at least some are more than 2 mm long, roundish, green on top and often purplish on bottom.
*Fruit: 0.8-1 mm long. Seeds with 8-15 distinct ribs.
*Habitat: Permanent, slow moving water of ponds, lakes, and streams.Turion Duckweed
- Lemna turionifera
*Compare to Lemna minor
*Fronds: 1-4 mm long, nearly oval, flat, green on top and bottom, sometimes red to purplish on bottom. Red to purple color emanating from the root.
*Turions: Produced under stress. Olive, brown, or dark green rootless disk-like, 0.8-1.6 mm wide, that sink.
*Fruit: 0.5-0.6 mm long. Seeds with 30-60 distinct ribs.
*Habitat: Calm waters.Pale Duckweed
- Lemna valdiviana
, native, SOC
*Fronds: 1-2 mm long, oblong, green on top and bottom.
*Habitat: Warm Springs; possibly also lakes and rivers.Inflated Duckweed
- Lemna gibba
*Fronds: Less than 6 mm long, nearly oval, greenish on top and bottom or red to purplish on bottom. Red to purple color emanating from the margins.Inflated which can be seen in cross-section, making their lower surface convex.
*Habitat: Calm waters of ponds and lakes.Star Duckweed
- Lemna triscula
*Fronds: 6-12 mm long, oblong to lanceolate and attached together by elongated stipes to appear like a 'canoe paddle', and greenish on top and bottom.
*Veins: 3 and faint.
*Habitat: Fresh to somewhat alkaline water of ponds, lakes, and marshes.
Species of the Duckweed Family are used for waste-water purification and as test- and indicator- plants for detecting certain conditions (Landolt in FNA 2000).