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Wetlands

Vernal Pools

Vernal pool, Rowena Plateau, Wasco County

Vernal pool, Rowena Plateau, Wasco County
(John A. Christy, Oregon Biodiversity Information Center)

Vernal pools are one of Oregon's rarest wetland types. They form on impervious basalt bedrock or on soils cemented by a calcareous or siliceous hardpan that impedes drainage. Pools can range in size from an acre (0.4 hectares) or more to patches as small as 10-225 square feet (1-5 square meters), and may occur singly or in groups covering many acres. They usually fill with water in the fall or winter and dry up in spring or early summer, but seasonal precipitation may be highly variable and pools may fill for only brief periods or not at all. They are home to a large variety of plants and animals adapted to these harsh conditions, and some species are rare globally. Vernal pools are threatened primarily by urban or suburban development on the typically flat and easily accessible landforms in which they occur.

Vernal Pools Map

Vernal Pools



Habitat: Small to large depressions on flats or irregular surfaces, drainage constrained by bedrock or hardpan
Water regime: Intermittently to seasonally flooded
Water chemistry: Fresh



Ecoregion*: BM = Blue Mountains, BR = Northern Basin and Range, CB = Columbia Basin, CR = Coast Range, EC = East Cascades, KM = Klamath Mountains, WC = West Cascades, WV = Willamette Valley  
  Scientific & Common Name Global & State Rank Ecoregion*
wetland type image Alopecurus saccatus-Plagiobothrys bracteatus Vernal Pool [Provisional]
Saccate foxtail-bracted popcorn flower (Titus 1996-1998: 6)
G2S2 KM
wetland type image Camassia quamash - Triteleia hyacinthina Vernal Pool [Provisional]
Common camas - hyacinth triteleia (Borgias 2004, App. 3: 10)
G1S1 KM
wetland type image Danthonia unispicata - Poa secunda Wet Meadow
One-spike oatgrass - Canby's bluegrass (Björk 2011: 25; NS)
G3S2 BM, EC
wetland type image Deschampsia danthonioides Vernal Pool [Provisional]
Annual hairgrass (Titus 1996-98: 5; Borgias 2004, App. 3: 10)
G2S2 KM
wetland type image Deschampsia danthonioides - Danthonia unispicata Vernal Pool [Provisional]
Annual hairgrass - onespike oatgrass (Johnson & Simon 1987)
G3S2 BM
wetland type image Deschampsia danthonioides - Lasthenia californica Vernal Pool [Provisional]
Partridgefoot - Tolmie saxifrage (NS)
G1S1 KM
wetland type image Deschampsia danthonioides - Plagiobothrys leptocladus Herbaceous Vegetation [Provisional]
Annual hairgrass - slender-branched popcorn flower (Meinke & Magee 1986: 34)
G2S2 CB
wetland type image Downingia elegans Herbaceous Vegetation [Provisional]
Common downingia
G2S1 WV
wetland type image Downingia yina Vernal Pool [Provisional]
Willamette downingia (Titus 1996-1998: 5; Borgias 2004, App. 3: 10)
G2S2 KM
wetland type image Downingia yina - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Willamette downingia-bracted popcorn flower
G2S2 KM
wetland type image Eryngium petiolatum - Grindelia nana Vernal Pool
Coyote-thistle - low gumweed (NS)
G1S1 KM
wetland type image Eryngium petiolatum - Lasthenia glaberrima Vernal Pool
Coyote-thistle - smooth lasthenia (Borgias 2004, App. 3: 10; NS)
G1S1 KM
wetland type image Eryngium petiolatum - Navarretia leucocephala ssp. leucocephala Vernal Pool [Provisional]
Coyote-thistle - white flowered navarretia (Borgias 2004, App. 3: 10)
G1S1 KM
wetland type image Gratiola ebracteata - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Bractless hedge-hyssop - bracted popcorn flower
G2S2 KM
wetland type image Isoetes bolanderi Vernal Pool [Provisional]
Bolander's quillwort (Titus 1996-1998: 6)
G1S1 KM
wetland type image Isoetes nuttallii Wet Meadow
Nuttall's quillwort (Christy 2004: 123; NS)
G3S3 WV
wetland type image Isoetes nuttallii - Plagiobothrys bracteatus Vernal Pool [Provisional]
Nuttall's quillwort-bracted popcorn flower (Titus 1996-1998: 6)
G2S2 KM
wetland type image Marsilea oligospora - Eleocharis acicularis Vernal Pool [Provisional]
Pacific waterclover - needle spikerush (Björk 2011: 26)
G2S2 EC
wetland type image Navarretia intertexta - Polygonum polygaloides spp. kelloggii Vernal Pool [Provisional]
Needle-leaf navarretia - Kellogg knotweed (Johnson & Simon 1987: 224)
G2S2 KM
wetland type image Navarretia leucocephala ssp. leucocephala Vernal Pool [Provisional]
White flowered navarretia (Borgias 2004, App. 3: 10)
G2S2 KM
wetland type image Navarretia leucocephala ssp. minima - Polygonum polygaloides ssp. confertiflorum [Provisional]
Least navarretia - closeflowered knotweed (Björk 2011: 25)
G2S2 EC
wetland type image Plagiobothrys figuratus Vernal Pool
Fragrant popcorn-flower (NS)
G1S1 WV
wetland type image Plagiobothrys leptocladus - Veronica peregrina Vernal Pool [Provisional]
Slender-branched popcorn flower - purslane speedwell (Meinke & Magee 1986: 34)
G2S2 CB
wetland type image Psilocarphus brevissimus Vernal Pool [Provisional]
Dwarf wooly-heads (Titus 1996-1998: 5)
G2S2 KM

Authored by John A. Christy, Wetlands Ecologist, (ORBIC) Oregon Biodiversity Information Center (2012 rev. 2017)