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Field invaded by ventenata/ Credit: Inna Smith
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Patch of ventenata/ Credit: Inna Smith
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Single ventenata plant/ Credit: Inna Smith

Ventenata (Ventenata dubia), also known as Africa grass, or simply wiregrass is a new invasive in the Pacific Northwest. It is a problem in rangelands where it outcompetes native species important to livestock. This is a tricky plant that can be hard to identifiy, so pay close attention to the identification guide. 

 

Identification Guide: Ventenata dubia

Identification: 

Ventenata is a winter annual that germinates in the fall. Plants initiate seed production from May-June, and mature seeds are produced from June to mid-July, depending on the locality and habitat conditions. Young seedlings have leaves that appear-rolled or folded lengthwise and narrow. The plant can grow to be 10-46cm tall. Young plants appear silvery green, but rapidly mature to a yellowish-tan color. The reproductive structure of a plant is referred to as a panicle, and the side-branches of the panicle are long and droop downwards when the plant is mature. At the end of each drooping side-branch are 1-5 spikelets (1-1.5cm). Each spikelet produces several seeds, and the seeds of ventenata can be identified because of their missile-shaped appearance, bent awns, and the presence of rib-like veins (Fig 1). Other discerning characteristics include a black “collar” at each of the nodes along the stem, with the black collar most visible at the base of the stem (Fig 2).  Another characteristic used to identify ventenata is its unusually long ligule (Fig 2), which is a membranous tissue located at the junction of the blade and the sheath of the leaf.  Ventenata is often confused with a grass native to the USA called Deschampsia danthonioides (annual hairgrass), which is similar in appearance except for having smaller, oval-shaped seeds (Fig 3).  In addition, ventenata is often mistaken for cheatgrass, especially after cheatgrass has dropped its seeds

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Fig 1. How to identify ventenata. Credit: Dorothy Maguire

 

Background: Ventenata dubia, also known as ventenata, wiregrass, or North Africa grass, is native to most of Europe, parts of North Africa and extending eastward into central Asia. While it is rare in most of its native range, it has become a highly invasive weed in grasslands and rangelands in western North America, particularly the Pacific Northwest. Ventenata was first collected in eastern Washington in 1952. Since its introduction, the grass has rapidly increased its distribution, and it is now causing serious ecological and economic harm in eastern Washington, Idaho, Oregon, Montana, and more recently, northern California. The rate of spread of this species is notable, for example since the 1950’s it has become invasive in over 46 counties, and is estimated to spread at a rate of 1.2 million hectares per year.

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Fig 2. Some key characteristics used to distinguish ventenata from other plants. Credit: Dorothy Maguire

 

Impact: Ventenata is known for displacing native vegetation along roadsides, as well as pastures and rangelands.  The species causes its greatest economic harm after invading fields used for grass seed production and fields used to produce timothy grass hay. Like other invasive grasses, ventenata is worthless as forage because it is not palatable to livestock, or wildlife.  With the invasion of ventenata, the coverage of native perennial grasses and forbs is sharply reduced (native biodiversity decreases).  Furthermore, due to its shallow root system, the presence of ventenata increases soils erosion. Control methods currently consist of herbicide treatments over multiple years.  The feasibility of using biological control in the management of ventenata is currently being investigated.

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Fig 3. How to tell ventenata apart from its look alike. Credit: Dorothy Maguire