Najas graminea
Rice-field water-nymph, Rice-Field Water-Nymph
(c) 胡正恆(Jackson Hu), some rights reserved (CC BY) · licence
Family: Hydrocharitaceae · Type: Herb · Not Native
Najas graminea (Rice-field water-nymph) is a non-native California herb in the Hydrocharitaceae family, recognized by intermediate leaf tooth count and deep-lobed sheath tips.
Rice-field water-nymph is a naturalized annual found in the Sacramento Valley, specifically in Butte and Colusa counties, inhabiting irrigation ditches and rice fields at elevations below 150 meters. Flowering from June to August, this aquatic plant has small flowers with distinctive features. Growing as a monoecious species with slender stems, it develops leaves with approximately 40 teeth along each margin and acute tips. Its leaves have deeply lobed sheaths, creating a delicate underwater structure. The tiny seeds are fusiform with a pitted, dull coat measuring 0.4 to 0.6 millimeters wide.
Identification and appearance
Key characters: 2 sympatric species; distinguished by intermediate leaf tooth count and deep-lobed sheath tips
Habitat and range
Habitat: Uncommon. Irrigation ditches, rice fields
Elevation: < 150 m
Outside California: Africa, Australia, native to tropical Asia
Bloom period
Najas graminea blooms Jun-Aug.
How to tell it apart
vs Hydrilla: Najas leaves have obvious teeth along margins; Hydrilla has spiny bumps on the leaf midrib underneath.; vs Elodea: Najas leaves are arranged opposite or in whorls of many; Elodea has 2-3 leaves at stem base, 3-7 higher up.; vs Egeria: Najas has tiny leaves under 1.5 cm; Egeria leaves are much larger (1.2-4 cm long).; vs Ottelia: Najas is completely submerged with tiny flowers; Ottelia has floating leaves and showy white flowers above water.; vs Limnobium: Najas is fully submerged with narrow toothed leaves; Limnobium has round floating leaves on spongy stalks.
Frequently asked questions
Is Najas graminea native to California?
No. Najas graminea is not native to California (recorded as not native).
When does Najas graminea bloom?
Najas graminea blooms Jun-Aug.
What plant family does Najas graminea belong to?
Najas graminea is in the Hydrocharitaceae family, genus Najas.
What habitat does Najas graminea grow in?
Najas graminea grows in Uncommon. Irrigation ditches, rice fields.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.