Two plants found in Arizona that are similar in appearance are (links) Lupine and Locoweed.  There are several species of each plant. They are both members of the Fabaceae, or Pea Family.  They have another similarity: they are both very toxic.

Cattle, sheep, horses and goats all have died from the effects of eating these plants.

First let’s look at Locoweed.  

Locoweed, Oxytropis lambertii

Locoweed poisoning is the most widespread poisonous plant problem. Look closely at the leaves of Locoweed.  They grow in clumps close to the ground and each leaf has 19-29 leaflets attached in pairs.  They are covered with soft, fine hairs.  There are 300 species of locoweed. Pictured is only a single species, native to northern Arizona. Locoweed contains toxic levels of swainsonine, a poisonous alkaloid. There has been extensive loss of range animals caused by eating locoweed.  Horses in particular seek out Locoweed and become addicted.  Signs of poisoning may not immediately appear, even for months.  Then horses quickly die from damage to brain, digestive organs, or congestive heart failure.

The second plant is Lupine: 

Lupine, Lupinus argenteus

Examine the leaves of the Lupine. Each leaf is palmately compound. It looks like your palm with fingers splayed. There are 5-7 leaflets to each leaf. Lupine is also toxic. The seeds and pods are the most toxic parts.  Poisoning with Lupine can cause nervousness, foaming at the mouth, depression, reluctance to move about, birth defects, difficulty in breathing, twitching leg muscles, loss of all muscular control, convulsions, coma and death.

The flowers on both plants are remarkably similar, since they are all in the Pea Family.  They are a beautiful blue addition to the flora, but be cautious about handling them, and don’t you or your animals eat them.