Spotted Spurge (Chamaesyce maculata) – Its central taproot can grow to two-feet deep. A thick milky sap oozes from broken stems and leaves. Beware: the sap is caustic and can cause severe, painful inflammation and blistering to skin, mouth, nose and eyes. It can be toxic to animals and harbor stinging ants. One plant produces up to 3,000 seeds. Viable for years, the exact duration unknown.