Lupine is dangerous from the time it starts to grow in the spring until it dries up in the fall. Younger plants are more toxic than older plants; however, plants in the seed stage in late summer are especially dangerous because of the high toxin content of the seeds. Lupine is also more palatable than the dried pasture grasses in the late summer.
The amount of lupine that will kill an animal varies with the lupine species and the stage of plant growth. A sheep that is getting good forage may not be affected by occasionally eating a small amount of lupine ( about 1/8 to ¼ lb.), but a sheep is usually poisoned if it eats 1/8 to ¼ lb. of lupine daily for 3 to 4 days.
Cattle may be poisoned by eating 1 to 1 ½ lbs. of lupine without other forage. Smaller amounts are poisonous if cattle eat the weed daily for 3 to 7 days. If cows consume the plant between days 40 and 70 of gestation, their calves will often suffer from crooked calf disease. These calves are born with cleft palates, crooked legs and distorted /malformed spines. Epidemic outbreaks of such birth defects can have high morbidity resulting in enormous animal and economic losses.
Lupine is frequently planted and an attractive plant in the garden. It has not been browse before- I've lived here 11 years. Recently, I planted three more and... One got eaten to the ground. It would be nice if our pesky resident vole was the culprit.
Good lord, didn't know that it was that toxic. Will keep away from the dogs if I try it again (short time perennial here). May put up restaurant sign for the voles though,,going through my trillium patch today!!!!
The toxicity is a problem with grazing animals where the ingestion amounts could get high. I would not stop planting lupine, as a garden decoration; but when it grows rampant through fields intended to support those grazing animals, someone needs to be in charge.