Ageratum houstonianum is a herbaceous perennial plant but it is mostly treated as an annual in most gardens. Interestingly Ageratum in Greek means long-lived. It is also known as Mexican Paintbrush, Flossflower, BlueMink, Blueweed, or Pussyfoot. It is a very popular plant in beddings and landscapes in Southern California. Ageratum houstonianum is native to Central America, in particular Mexico, Guatemala, and Belize. It is part of the Asteraceae family of plants.
Mexican Paintbrush has a long flowering period and a unique color that complements the pinks, reds, and yellows of other flowers, perhaps that makes it a popular flower to mix in borders. The flowers appear from May to November and they are violet-blue in color, they appear in dense corymbs. Ageratum houstonianum grows from 6 to 24in or 15 to 60cm.
Plant Ageratum houstonianum in the sun in moist, humus-rich soil but well-drained. It does not like to dry out but it needs to be well drained. It can tolerate some shade.
Ageratum houstonianum or Mexican Paintbrush is toxic to grazing animals as it contains pyrrolizidine alkaloids that cause liver damage. It attracts butterflies but it is deer and rabbit resistant. Ageratum houstonianum is easy growing and you can propagate from seed. You can deadhead the flowers to keep it tidy but not as critical as it blooms for a long period.