Dalmatian toadflax (Linaria dalmatica) was introduced as an ornamental from the Mediterranean and has pretty yellow flowers that could be mistaken for a snapdragon. Its extensive and deep root system makes it very difficult to control or remove. Toadflax can crowd out native species and take over, which is why it is on several states’ noxious weed lists (1).
In addition to being deep, toadflax roots can produce buds that grow into new plants, so it is not dependent on seeds for dispersal. Toadflax establishes quickly in disturbed areas and does well in a variety of environmental conditions (2).