Pretty but poisonous

Sophora secundaflora (Texas mountain laurel)

The Texas Mountain Laurel is a lovely small tree with bunches of bright blue flowers. These flowers yield bright red seeds which Native Americans used as ornaments and jewelry, but also as an hallucinogen. The seeds can be used to make a drink which when dilute leads to hallucinations, but at higher doses is poisonous. The toxic compound, cytisine, causes paralyses which leads to suffocation.