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Water howellia

Photo of Water Howellia

Scientific name: Howellia aquatilis 

Status: Threatened

Critical Habitat: None

Listing Activity: Water howellia was federally listed as threatened without critical habitat in 1994 (U.S. Fish and Wildlife Service 1994). A recovery plan has not yet been published for this species.

Potential Range Map 

  • Description and Life History

    Water howellia is an annual aquatic species in the bellflower family (Campanulaceae). Individuals are mostly submerged and rooted in bottom sediments. Stems branch near the soil surface and are 4-7 dm (16-28 in) long. The leaves are numerous and linear to linear-filiform, measuring1.0-5.0 cm (0.4-2 in) long, with an entire margin or with a few teeth. The flowers are axillary, 2-2.7 mm (0.8-1.1 in) long, and a corolla is present (in emergent flowers) or lacking (in underwater flowers). The corolla is white to pale lavender and is deeply cleft on one side. The fruit is 8-10 mm long (0.3-0.4 in). The seeds number 1-5 and are 2-4 mm (0.1-0.2 in) long. This species typically blooms May through August.


    Information on herbarium labels or Oregon collections describe the habitat as "ponds in woods", "pond in shaded woods", and "stagnant ponds in the timber". Information from other locales indicate that this species is restricted to small, vernal, freshwater wetlands, glacial pothole ponds, or former river oxbows that have an annual cycle of filling with water over the fall, winter and early spring, followed by drying during the summer months. These habitats are generally small (<1 ha [2.5 ac]) and shallow (<1 m [3 ft] deep). Bottom surfaces are reported as firm, consolidated clay, and organic sediments. Most locations were surrounded by deciduous trees and howellia was found in shallow water or around the edges of deep ponds. Associated species include duckweed (Lemna spp.), water starworts (Callitriche spp.), water buttercup (Ranununculus aquaticus), yellow water-lily (Nuphar polysepalum), bladderwort (Utricularia vulgaris), and pondweeds (Potamogeton spp.)

    Reasons for Decline

    In Oregon, sites where water howellia were historically found are now within developed urban areas. Channelization and construction of dams along the Columbia, Willamette, and other rivers has led to loss of suitable wetland habitats. The historical California population may have been eliminated by cattle grazing and trampling. Idaho bottomland habitats have been altered by roads, development, and conversion to agriculture and pasture lands. Timber harvest, wetland succession, and encroachment by non-native plants such as reed canarygrass (Phalaris arundinaceae) have also contributed to the decline of this species.


    Water howellia is known to occur sporadically in Washington, Idaho, Montana, California, and Oregon. However, the species has historically been collected (voucher specimens in herbariums) from at least four different places in the state. It was first collected in 1879 from Sauvies Island, Multnomah County. It was collected from Sauvies Island again in 1886, but not since then. It was also collected from Lake Oswego in Clackamas County in 1892. It was collected from two places in the Salem area, most recently in 1977. Numerous attempts to relocate these sites have been unsuccessful. The historic Oregon sites were all located within the Columbia River floodplain or the broad valley of the Willamette River.

    References and Links

    U.S. Fish and Wildlife Service. 1994. The Plant, Water Howellia (Howellia Aquatilis), Determined To Be a Threatened Species. Federal Register 59:35860-36864.


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