Seeley Swan Pathfinder -


By Lindsey Bona-Eggeman
Missoula County Weeds District 

Ventenata - An annual pain in the grass


Jane Mangold, MSU Extension

Ventenata infestation.

A new annual invasive grass is on the horizon, literally. Just down the highway from the town of Seeley Lake, Ventenata dubia is taking hold along our roadways.

Though Ventenata is newly arriving in our corner of the county, it is increasingly becoming widespread in the state of Montana. New populations are being identified every summer and current populations seem to be moving/growing at a rapid pace. Land managers around the West are reporting this invasive grass to be more challenging to manage and more aggressive then cheatgrass. Implications of this tough to manage invasive grass are both ecological and economic.

Ventenata dubia is an annual grass that is native to southern Europe, western Asia and northern Africa. This invasive grass is known as a winter annual, which means that the seeds germinate mostly in the fall and overwinter as seedling grasses. This fall germination allows the plant to take early advantage of Montana's spring moisture.

The first documented sighting of Ventenata in Montana was in the 1990's. It is not currently listed as a noxious weed in the state of Montana. The distribution of Ventenata is not well documented here in Montana but positive identifications have increased across the state in the last couple of years.


Ventenata can grow from 6-18 inches tall. It has open sheaths, and the inflorescence is more or less lax, open and pyramidal in shape. The color of Ventenata has been described as tawny to light yellow. Grass identification can be difficult for many people, so look for these key characteristics on Ventenata: reddish-black nodes in May-June; unusually long, membranous ligule (1-8mm); distinct shiny appearance and open panicle in June-July; and lower awns that are straight and upper awns that are twisted and bent once the plant senesces in July-August.


Ventenata can commonly be found on south-facing slopes, with shallow rocky clay soils. In Western Montana we find this invasive grass on roadsides, rangeland and hay and pasture ground. It is very well adapted to Montana's cool wet winters and hot dry summers.


An infestation of Ventenata has the ability to produce up to 3800 seeds per square foot and each individual plant can produce up to 35 seeds. The awns on the seeds can easily attach to fur, clothing and equipment. Much of the infestations in the West are thought to have been introduced through contaminated forage. Here in Missoula County, our roadways seem to be a main vector for spread.


This invasive annual grass is not palatable to livestock and wildlife which means it can decrease forage quality when it invades pasture, hay fields and rangelands. The shallow root system of Ventenata can increase soil instability and promote erosion. Ventenata competes with perennial grasses creating significant ecological and economic impacts.


The lack of good management strategies is one of the reasons this invasive grass is so troublesome. Mowing is ineffective and at times promotes a secondary germination flush. The plant is not palatable to livestock which makes grazing not an option.

Land managers are seeing some success with chemical applications typically used for cheatgrass and Japanese brome, such as Plateau, Esplanade and Outrider. These applications can present some injury to established perennial grasses and impact revegetation efforts.

Ventenata Distribution

Ventenata is not currently listed as a noxious weed in the state of Montana but is proposed to be added to the list this spring.

Keep your eyes open this summer for this newly invading annual grass. Protect your own land from invasions of noxious weeds by, promoting healthy perennial grass populations. Prevent the introduction of new species by knowing where your forage comes from and consider purchasing weed-seed-free forage. Limit ground disturbance by not overgrazing. Where ground disturbance is necessary, reseed with desirable vegetation.

Information for this article was obtained from the following sources:;


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