June weed of the month: Dalmatian toadflax
A perennial plant native to the Mediterranean is June’s Weed of the Month. Dalmatian toadflax (Linaria dalmatica) was brought to the western U.S. as an ornamental, escaped cultivation and has become a noxious weed throughout many western states.
Dalmatian toadflax invades and overtakes grasslands, rangelands, pastures, natural areas, and disturbed areas. These infestations have reduced livestock production, land values, biodiversity and wildlife habitat.
Dalmatian toadflax is a short-lived perennial with waxy, bluish-green stems and leaves. The weed has yellow flowers, sometimes with orange centers, arranged on spikes that look similar to a snapdragon. The plant can grow to four feet. It prefers sunny areas with well-drained, coarse-textured soils. Dalmatian toadflax spreads by seed and by lateral roots.
Yellow toadflax, also called butter-and-eggs (Linaria vulgaris), is a Dalmatian toadflax look-alike and is commonly found in Minnesota but has small, narrow, linear leaves compared to Dalmatian toadflax’s thick, waxy, heart-shaped leaves.
Yellow toadflax is also considered to be a weedy species but is far less aggressive and damaging than Dalmatian toadflax and is not regulated under the noxious weed law.
In Minnesota, Dalmatian toadflax, thought to only be in Kittson County, was recently discovered in Cook County. Ongoing efforts in Kittson County to eradicate Dalmatian toadflax brought together Kittson County, the Nature Conservancy, private landowners and the Minnesota Departments of Agriculture, Natural Resources and Transportation.
Dalmatian toadflax’s thick, waxy leaves resist the penetration of many herbicide formulations, making it a challenging noxious weed to treat. Mowing is not recommended because equipment can spread seed and root fragments.
Hand pulling individual plants can be effective in light or moist soils that allow removal of the entire root, but gloves should be worn for all hand pulling.
For herbicide recommendations, contact University of Minnesota Extension or a local county agriculture inspector.