This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Native. Perennial. Propagates by seeds.
Time of bloom: June to August.
Seed-time: August to October.
Range: California, Idaho, and Montana, northward to Alaska.
Habitat: Foothills and mountain valley pastures to an altitude of about nine thousand feet.
The chief sufferers from this noxious plant are cattle, since sheep are seldom driven to the mountain pastures before July and by that time the plant has grown too large and coarse for their cropping and is besides less virulent than in its younger stages. It is when the tufted base leaves first appear in April and May that they are most dangerous and also most succulent and tempting to stock.. Frequently the danger is increased by the fall of light spring snows, which cover the young grass, and the Larkspur's taller foliage is the only forage showing green above the snow.
Stem four to seven feet tall, stout, simple, ridged, and covered with a white bloom (glaucous). The base leaves which first rise from the thick, woody roots are long-petioled, smooth, glaucous, four to six inches broad, rounded in outline, five- to seven-lobed, the segments rather broad, long-pointed, and deeply cut; the lower stem leaves are smaller, with fewer lobes, becoming simple and lance-shaped as they ascend the stalk. Raceme terminal, long and slender, the flowers numerous, rather small, pale blue or white. Follicles in threes, smooth, erect, tipped with a short beak; the seeds are black.
Herding cattle away from places where the plant abounds during the spring months, when it is most dangerous. But in some localities it is considered that extermination by digging would be feasible and a paying investment of labor. An instance is given by Chesnut1 and Wilcox of a Montana range where forty cattle had died in a single month from eating this plant. "A careful inspection of this range showed that the Tall Larkspur was entirely confined to a few areas of small size. It is believed that it could all be completely exterminated by twenty-five days' work with a weed digger designed for severing the roots at a short distance below the ground. The expense of this labor would not exceed the value of two cattle and this number is much less than the average annual loss from the Tall Larkspur on this range." Similar conditions prevail on many other ranges.