Common Tansy, photo credit: Jerry R. Oldenettel
Common Tansy is also known as golden buttons and garden tansy. Common tansy was introduced from Europe into colonial North America in the 1600’s as an ornamental plant and for medicinal uses. Ironically, common tansy contains alkaloids that are toxic to humans and livestock if consumed in large quantities. Common Tansy was first discovered in Silver Bow County in 1936.  Common tansy is a big problem in most counties on the roadsides, ditches, and waste areas.
Concerns Common tansy is unpalatable to livestock and mildly poisonous.  The presence of this weed reduces species diversity, wildlife habitat, and livestock forage. It has a tendency to grow near water, which allows the plant to spread easily and makes control difficult. The root system on common tansy allows the plant to spread laterally and by broken pieces of roots.
Identification Common tansy is a perennial forb that can reproduce by rootstalk or seed. One of the most notable features of tansy is the potent smell cause by crushing the leaves. The flowers on common tansy are yellow-orange button-like flower heads. Flowers of the common tansy are numerous; there can be 20-100 flowers in flat-topped, dense clusters. The leaves on the common tansy are deeply divided into leaflets with toothed margins, almost fern-like. The leaves are alternately arranged and are uniform in size. This plant will grow between 1-6 feet tall and the stem is often a purplish-red color.
What can you do? Due to the extensive root system of common tansy an integrated management approach is necessary.  Preventing the spread of this weed into new areas is one of the easiest management techniques.  Mowing and hand-pulling has marginal results due to the root system of tansy and they are best used in combination with other controls. Mowing and pulling will help prevent seed production. Maintaining healthy desirable vegetation will aid in controlling common tansy. Grazing in infested areas should be monitored closely to maintain desired species. There are a couple of effective chemicals for common tansy.  For recommendations on those, call the weed district,
Visit the MWCA Weed ID pages for additional information and pictures of common tansy.
This series of articles was developed by Ravalli County. If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.
Tags: Common Tansy, Montana's Noxious Weed List, Priority 2B Weed, Tanacetum vulgare