Water howellia is a delicate, glabrous aquatic annual with a flaccid, somewhat fistulose stem. Plants are 10-70 cm long, rooted, naked below, and branched above, the branches spreading or floating. Leaves are narrowly linear, mostly entire or with a few slender teeth, flaccid, and 1-4.5 cm long by up to 1.5 mm wide. Early flowers are submerged, cleistogamous (remaining closed), lack a conspicuous corolla, and are located in the axils of ordinary leaves. Later flowers are emergent, borne on specialized branches with shorter and more or less verticillate leaves, and are chasmogamous (opening at maturity), bearing lavender or whitish deeply dorsally cleft and 5-lobed tubular corollas 2-3 mm long. Capsules are 0.5-1.3 cm long.
Water howellia is typically found at the edges of low-elevation vernal pools, generally in shaded areas.
Limiting factors
Habitat loss due to agricultural and urban development and changes in wetland hydrology pose significant threats to this species. Displacement by invasive plants (e.g., reed canary grass, purple loosestrife) and aquatic vegetation succession can also adversely affect water howellia.
Data gaps
Develop propagation and transplanting protocols. Conduct long-term demographic studies. Investigate seed viability and distribution mechanisms. Conduct seed bank studies and develop methods for storing viable seeds.
Conservation actions
Maintain or restore seasonal wetland habitat. Control invasive plants at priority sites. Conduct surveys of potential habitat to locate additional populations. Protect existing populations to maintain genetic diversity. Continue post-delisting monitoring.
Key reference or plan
A U.S. Fish and Wildlife Service draft Recovery Plan released for water howellia in 1996. https://ecos.fws.gov/docs/recovery_plan/960924.pdf
Post Delisting Monitoring Plan: https://ecosphere-documents-production-public.s3.amazonaws.com/sams/public_docs/species_nonpublish/22782.pdf
