Weed of the Week: Indigobush (Amorpha fruticose)

Indigobush is a Class B Weed native to Eastern and Central United States. This weed is known to be toxic to humans & livestock and is listed on the Washington State quarantine list.

Although native to the Eastern United States, in some Western states it is considered invasive and has naturalized. It escapes planted areas and grows along streams, rivers, and prairie draws forming dense thickets that outcompete native species.

Indigobush is a thornless, deciduous, multiple stem shrub that can grow to over 12 feet tall and can form thickets. Flowers are in dense, upright clusters, in the upper branches. They are blue violet to dark purple and have 10 stamens. Older stems are woody, and younger stems are green and hairy.Seed pods are small, curved, dark brown about ¼ inch in size and are dotted with glands. Each pod contains 1 or 2 seeds. Indigobush grows in prairies, hillsides, sandy roadsides, and along streams. The plant reproduces by seed.

Cutting plants may result in re-sprouting stems. Repeated cutting may be used to control seed production each year. Seedlings and small plants may be pulled or dug out of the ground. Large plants can have extensive root systems for which digging may not be feasible.

If you have any questions regarding Indigobush or how to identify other toxic weeds, please call Andy Lea, the Wahkiakum County Noxious Weed Control Coordinator at 360-795-3852.