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Lyme grass or sand ryegrass

(Leymus arenarius or Elymus arenarius)

Photo of Lyme grass
Photo credit: Wisconsin DNR

An invasive grass in coastal regions. Its form of fast vegetative growth can negatively affect native beach and dune vegetation. As Lake Michigan's water levels have gone down, more areas have been colonized by this species. Stems are smooth, round and stout; the plant is 2-4’ tall.


Other names for this plant include:
  • Common names: Sand ryegrass
  • Scientific names: Elymus arenarius
Ecological threat:
  • It can grow in a variety of habitats but is especially concerning on the shores of the Great Lakes. With a spreading root system, lyme grass can stabilize our naturally shifting dunes and compete with rare grasses.
  • Occupies the same dune habitat and poses a threat to several native rare plants which include: Elytrigia dasystachya, Calamovilfa longifolia, Salix cordata, Cirsium pitcheri, Solidago simplex, Cakile lacustris, and Euphorbia polygonifolia.
Overview map of Lyme grass classification in WI
Prohibited (red) and restricted (orange) counties

Classification in Wisconsin: Prohibited/Restricted (Restricted in Door, Kenosha, Kewaunee, Manitowoc, Milwaukee, Ozaukee, Racine and Sheboygan counties; Prohibited elsewhere).

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for lyme grass was based upon this literature review [PDF] developed by the department.


Leaves: Broad, rigid, straight, with a short ligule; blueish in color. 12” long and 0.5” wide.

Flowers: Dense spikes with 3 flowered spikelets; glumes are not longer than the spikelets. Flowers in July. Spikes are blue-green in early summer and turn beige later in the season.

Roots: Rhizomes.

Similar species: American dune grass (Ammophila breviligulata Fernald) has green leaves and is less robust. Thick-spike wheatgrass (Elymus lanceolatus) is very similar in size and color but has a spike thickness of 5-10 mm compared to lyme grass which has a spike thickness of 15-25 mm. There are more characteristics within the inflorescence that can help discern the two species and others, however, please refer to a regional biologist for identification.


Mechanical: Not recommended control.

Chemical: Foliar treat stems with Habitat (Imazapyr) herbicide mixed with Tactic surfactant at a rate of 1.5 ounces of each product per gallon of water. Applications may be made as early as June through early October as long as the leaves are still green. Several applications may be needed.


View lyme grass pictures in our photo gallery!


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