Page 888 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

846 SECTION | XIV Poisonous Plants

VetBooks.ir switched to grazing steers because of decreased reproduc- prominent spur; petals smaller and variable among spe-
cies, usually four and sometimes two, with the upper pair
tive efficiency in cows. Sheep appear to be more resistant
projecting back inside the spur; and carpals one to five,
to chronic selenosis compared to cattle and are better
adapted for some of these ranges. However, sheep are sometimes fused, ripening into many-seeded follicles.
sensitive to acute selenium poisoning, as was observed The tall larkspurs (Figure 61.2) are 1 or 2 m tall or
when a large number of sheep died within days after graz- more, flower in summer, and set seed in late summer,
ing on mine reclamation sites that contained very high subsequently senescing in the fall. In the west, the tall
soil and plant selenium concentrations (Panter, personal larkspurs typically inhabit higher mountain elevations in
communications, 2004). Monitoring for selenium concen- the more open moist areas of canyons, draws, and mea-
trations and forms in soil, vegetation, as well as animal dows. Delphiniums are frequently confused with
tissues and hair can help avoid poisoning incidences. Aconitum, but certain features distinguish them. As
Likewise, deficiency problems can be rapidly resolved implied by the common names, Delphiniums have a dis-
with frequent monitoring and supplementation. tinct spur (hence larkspur), whereas Aconitum has no spur
but a hood (hence monkshood). Tall larkspurs have hol-
LARKSPURS (DELPHINIUM SPP.) low stems, and their leaves are relatively long petioled,
whereas monkshood has stems that are solid and pithy
There are more than 80 wild species of larkspurs in North and leaves are short petioled.
America, and there are a larger number of domestic horticul- Low larkspurs (Figure 61.2) appear similar to tall lark-
tural varieties. Wild larkspurs are classified into three gen- spurs except they grow in different habitats and locations
eral categories based primarily on mature plant height and that is, lower elevations in drier habitats, on foothills and
distribution: low, tall, and plains larkspurs (Figure 61.2). flats. They appear first as a rosette-like clump in early
The dominant larkspur species in the western United States spring, soon producing an erect flowering stem, usually
are shown in Table 61.2. The larkspurs are a major cause of not more than 1 m in height, and then die back in early
cattle losses on western ranges. As early as 1913, C.D. summer.
Marsh reported that more cattle deaths on western ranges Plains larkspur falls between the low and tall larkspur
are caused by Delphinium spp. than by any other poisonous classifications. Plants range from 0.3 to 2 m tall. It grows
plant except locoweed. on the short-grass plains of Wyoming into Nebraska and
in the sagebrush and juniper woodlands of the Colorado
Description Plateau.
Most of the wild larkspurs have flowers of blue or purple,
bilaterally symmetrical, in erect terminal racemes or pani- Distribution and Habitat
cles: five sepals, the upper prolonged backwards in a
Low larkspur
D. nelsonii Idaho, South Dakota, Wyoming,
Colorado, and Utah
D. bicolor North Dakota, Montana, Wyoming,
Oregon, and Washington
D. andersonii Oregon, California, Nevada, Utah, and
Idaho
D. tricorne Nebraska and Oklahoma eastward
D. virescens Great Plains, east of the Rockies
Intermediate larkspur
D. geyeri Colorado, Wyoming, Nebraska, and Utah
Tall larkspur
D. barbeyi Utah, Wyoming, Colorado, and New
Mexico
D. occidentale Washington, Idaho, Wyoming,
Nevada, Utah, and Colorado
D. glaucescens Idaho and Montana
D. glaucum Washington, Oregon, California,
Nevada, Idaho, and Montana
FIGURE 61.2 Low larkspur (Delphinium bicolor) is on the left and tall D. trolliifolium Washington, Oregon, and California
larkspur (D. barbeyi) is on the right. D. robustum Colorado and New Mexico