Lupinus caudatus

Lupinus caudatus is a cool-season herbaceous perennial plant. It develops a thick, deep taproot topped with a woody structure at the base of the stems at the top of the root at or just below ground level (a caudex). From this caudex it has flowering stems that may be branched or unbranched. Most of its leaves grow on individual leaf stems at the base of the plant (basal leaves) which are long. The stems may be branched or unbranched and end with a 4–10 centimeter long inflorescence (terminal raceme) with many flowers. The banner petal is covered with hairs (pubescent) on its back side and its front grove. The lower lip, also called the keel, is often at least partially fringed with hairs (ciliate). Though Lupinus species often interbreed or hybridize to form intermediate individuals, there are two characteristics that help to distinguish Lupinus caudatus from the very similar Lupinus argenteus. The combination of the short spur and with a hairy banner petal will most often serve to distinguish L. caudatus. Hybrids between them will have a shorter spur and usually have a smooth banner petal. Lupinus sericeus is also very similar, especially the variety L. sericeus var. utahensis, because it also has a hairy banner petal. It, however, will have more widely spaced flowers, lacks the spur, and does not have basal leaves with long stems when it is flowering. ==Taxonomy==

Lupinus caudatus was first scientifically described and named in 1863 by Albert Kellogg, one of the founders of the California Academy of Sciences. As of 2023 it is accepted as a valid species by Plants of the World Online (POWO), World Flora Online (WFO), and the USDA Natural Resources Conservation Service PLANTS database (PLANTS). On the other hand, it is often combined into Lupinus argenteus as one or more subspecies or varieties. Synonyms for it listed by POWO are Lupinus argenteus var. argophyllus (A.Gray) S.Watson, Lupinus argophyllus (A.Gray) Cockerell, Lupinus caespitosus var. argophyllus (A.Gray) S.L.Welsh, Lupinus caudatus subsp. argophyllus (A.Gray) L.Ll.Phillips, Lupinus decumbens var. argophyllus A.Gray, and Lupinus laxiflorus var. argophyllus (A.Gray) M.E.Jones. '''Lupinus caudatus subsp. caudatus''' As the nominate subspecies (autonym) it is accepted by the same authorities as the species. PLANTS records it in the western United States from the Pacific Ocean to the Rocky Mountains, excluding New Mexico, and also the state of Nebraska. However, POWO only has records for it in California, Nevada, and Oregon. '''Lupinus caudatus var. cutleri''' (Eastw.) S.L.Welsh This variety is also listed as accepted by WFO and PLANTS. Synonyms for it listed by POWO are Lupinus caudatus subsp. cutleri (Eastw.) L.W.Hess & D.B.Dunn and Lupinus cutleri Eastw. '''Lupinus caudatus subsp. montigenus''' (A.Heller) L.W.Hess & D.B.Dunn This variety is also listed as accepted by WFO and PLANTS. Synonyms for it listed by POWO are Lupinus argenteus var. montigenus (A.Heller) Barneby and Lupinus montigenus A.Heller. '''Lupinus caudatus var. utahensis''' (S.Watson) S.L.Welsh This variety is also listed as accepted by WFO, but not by PLANTS. Synonyms for it listed by POWO are Lupinus argenteus var. utahensis (S.Watson) Barneby and Lupinus holosericeus var. utahensis S.Watson. Names The species name is Latin meaning tailed (from cauda, tail) describing the short spur, a backward projection on the upper part of the sepals. This part is also called the outer floral cup (calyx) and this is the origin of the common name "tailcup lupin". It is also known by the common names "Cutler's spurred lupine" and "Kellogg's spurred lupine". ==Range and habitat==

Lupinus caudatus is found throughout the western United States from the Rocky Mountains to the Sierra Nevadas and Cascades from occurrences recorded in the PLANTS database. It also records it in the Texas panhandle, Oklahoma, Nebraska, and South Dakota. POWO also records it growing in North Dakota, but lacks records of it growing in Washington State, Nebraska, South Dakota, Oklahoma, Texas, or any part of Mexico. Conservation Lupinus caudatus was evaluated by NatureServe as globally secure (G5) in 2003. At the state level they evaluated it as critically imperiled (S1) in Arizona and apparently secure (S4) in Nevada, but has not yet evaluated its status for any other state as of 2023. ==Ecology==

Lupinus caudatus is eaten by elk, mule deer, whitetail deer, antelope, upland game birds, small non-game birds, and small mammals. Observational studies have not found native wild animals to be poisoned by it. Because it is one of the more palatable Lupinus species, it is also eaten by sheep, cattle, and horses, sometimes to their detriment. While it will also persist in mature landscapes, Lupinus caudatus is generally increased by disturbances. Many plants will survive wildfires and in the next season will set seed to recolonize the open landscape. While they are good at colonizing open ground and low fertility soils, they lack a dense mat of roots and so are ineffective at preventing erosion in disturbed landscapes. ==Toxicity==

Lupinus caudatus, like many of its relatives in the genus Lupinus, is responsible for the congenital deformation of cattle calves called "crooked calf" by ranchers. This condition is now more formally known as "lupine induced arthrogryposis" and its symptoms include flexure of the front leg joints, twisting of the neck, curvature of the spinal column, and cleft palate. L. caudatus and Lupinus sericeus were the first two species identified as causing crooked calf. The toxin in L. caudatus that is responsible for the disease is the quinolizidine alkaloid anagyrine, though some other species contain a different teratogenic compound. == References ==