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: April at southern limit of range, August at northern limit. Seed-time: June to October. Range: Minnesota to the Saskatchewan and British Columbia, southward to Texas and Mexico. Habitat: Prairies and foothills; wild pastures and meadows.
This plant not only has a far wider range than the preceding species, but also climbs higher up the mountain sides, being found in Colorado and Montana at an altitude of eight thousand feet. Where they grow in company, however, the Woolly Loco-weed is considered the more harmful.
The root is hard, thick, woody, and scaly, boring deeply into the earth; it is crowned with a thick tuft of nearly erect, odd-pinnate leaves, about four to eight inches long, with slender petioles and nine to nineteen narrow, lance-shaped leaflets, about an inch in length and covered with fine, silky, whitish hairs; stipules hairy, membranous, lance-shaped, united to the base of the petiole. The peduncles also rise from the crown, eight to twelve inches in height, holding the dense flower-spikes well above the leaves; the flowers are usually white, and where the plant is abundant large areas appear as though covered with snow; but in some localities, usually in the higher mountain regions, there is great variation, some flowers being pink, others yellowish or violet or purple; they are large, more than an inch long, slender, with erect, ovate
Fig. 172. - Stemless Loco-weed (Oxytropis Lamberti). X 1/4 standard, narrow, oblong wings, and keel tipped with a sharp, projecting point. (Fig. 172.) Pods sessile, imperfectly two-celled, very firm and leathery, densely hairy, long-pointed, and filled with small seeds which loosen and rattle about in the pods as they become dry.
Like the preceding plant, White Loco-weed can be killed by deep cutting from the root, well below the crown - as was demonstrated by a Montana ranchman who lost three hundred lambs out of a herd of two thousand in one season from Loco poisoning; the next year, while the plants were in bloom in May and June he hired two men to dig up the Loco-weeds on an area four miles square, the tools used being heavy, narrow, and very sharp steel hoes; the plants never sprouted again and no further losses from Loco occurred on his ranch.