Weed of the Month: Yellow Alyssum
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Allison Kosto
MSU Broadwater County Extension Agent
Although not a noxious weed, yellow alyssum, has been on the rise in Broadwater County and other areas of Montana. It is often one of the first forbs to bloom in the spring so watch for it early.
Description & Habitat
Native to Northern Africa and Eurasia, yellow alyssum was brought to the United States as a medicinal plant to cure hiccups, mental illness and rabies. It was first reported in Canada in 1896 but was believed to be in the United States even earlier. It is often grouped together with a sister plant, desert alyssum. Together, these two plants now infect 37 states and seven provinces. Even though yellow alyssum has been around for a while without any problem, it is suspected that the changing climate with intense droughts and mild winters has weakened native plant communities allowing yellow alyssum to expand. It is becoming problematic in rangeland, roadsides and other dry, gravelly areas.
A member of the mustard family, yellow alyssum is most often a winter annual which means the seeds germinate in the fall and then it produces seed and dies the following year. It can grow 3 to 10 inches tall with multi-stems branching from the base. Leaves are very small with tiny hairs invisible to the naked eye. The hairs help the plant retain moisture and give it a pale green color. Yellow alyssum has tiny yellow flowers and blooms in May and June. The flowers leave behind round seed pods along the stem of the plant.
Like other weeds, yellow alyssum can displace native and desired vegetation and decrease forage production and plant diversity. Oftentimes, it will co-exist with native or introduced grasses or forbs until the conditions are right such as a disturbance for it to increase and establish a dense population. It has a shallow-root system which can actually increase soil erosion when it outcompetes deep-rooted species. Yellow alyssum is unpalatable to livestock but is eaten by western harvester ants, rabbits, antelope and sage grouse.
Management
Little research has been done on yellow alyssum. Avoiding disturbance or overgrazing is often effective in preventing issues with the plant. Typically, full control is not necessary. Reducing the population in high-density sites can allow the desired species to come back but still leave a few plants to benefit wildlife.
As an annual species, yellow alyssum can often be controlled with cultural practices that prevent or limit seed production where practical. Hand pull, dig or hoe in the fall or early spring before flowering. Burning and mowing can also be effective if it prevents the plant from going to seed. However, the plant may still be able to produce seeds below the height of the mower blade. Mulch (at least 3 inches) is effective. Livestock will not graze the plant.
Herbicides can be effective. Fall applications are the most successful. The most commonly used chemicals include 2,4-D, Banvel, Cimarron Max, Escort, Milestone, Opensight and Oust. A mix of herbicides may provide maximum control. Always read and follow the entire label when applying herbicide. Common chemical names are used for clarity but does not imply endorsement of a product or brand.
For assistance on weed identification and management, contact the MSU Extension Office in Broadwater County at 406-266-9242.
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PhotoCredit: Allison Kosto Photo
Image 1 Caption: Yellow Alyssum
Allison Kosto Photo
