For western Colorado ranchers, the decision to sell cattle during tough times can hinge on a flower. Local cattle have developed immunity against the poisonous larkspur that live among more edible grasses. So a rancher culling a herd he can't afford to feed faces a problem restocking once economics improve: The replacements may die if they binge on the purple and pink larkspur.

That's the problem confronting Carlyle Currier, who owns a 4,000-acre ranch in Molina, Colo. and is mulling a decision to trim his herd of 500 Angus-Hereford-Charolais hybrids. Basic economics also worry him; he knows that he may well have to pay more later to buy replacement calves if the price per head of cattle rises from today's rock-bottom lows. But like many ranchers across the West and central plains, Currier has little choice. This year's record drought has made his operation untenable.