Dieffenbachias are easy houseplants and are known for their colorful, large leaves. The common name Dumb Cane results from a mouth numbing substance in the stem and leaves. Some people may get a skin rash from the plant's sap. This plant can be toxic if eaten. Most will grow 3 to 6 ft tall and 1 to 3 ft wide. Large, tropical looking leaves in many shades of green are marked with spots, stripes, dots or colored veins.