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The P&PDL Picture of the Week
for 10 March 2003



Wild Onions and Wild Garlic – A Nuisance in Wheat Fields and Lawns

Glenn Nice, Department of Botany and Plant Pathology, Purdue University
Bill Johnson, Department of Botany and Plant Pathology, Purdue University
Tom Bauman, Department of Botany and Plant Pathology, Purdue University
Glenn Hardebeck, Department of Agronomy, Purdue University

To the dismay of my friends, I love to eat onions and garlic. I think they add a wealth of flavor to any dish. However, their wild cousins are not always welcome in a person’s lawn or a producer’s field. The strong odor of onion can be smelled after cutting the grass. When harvested with the wheat, wild onion and wild garlic can taint the taste of the flour produced. In a pasture situation, when ingested by cows, wild onion and wild garlic can taint the taste of dairy products. Although I may not find this a problem, most consumers don’t want their bread or butter to taste like onions or garlic. Both plants can be problems in the spring when it is time to plant wheat.

Both are perennial plants meaning that they can come back year after year. Wild garlic is often the culprit of these two that will cause problems in crops, whereas wild onion may be more of a nuisance in the lawn. Wild onion (Allium canadense L.) and wild garlic (Allium vineale L.) are often confused. They both have long narrow leaves arising from basal bulbs. Oddly enough, wild onion is described as having a garlic smell and wild garlic often an onion smell, which does not simplify the confusion. Both plants have long narrow leaves which is why they are sometimes confused as grasses. Wild garlic will have 2 to 4 of these leaves where as wild onion is described as having more than 2. Wild onion’s leaves are flattish above, slightly convex below and not hollow. Wild garlic, on the other hand, has hollow leaves. When the bulbs are dug up wild onion appears to have reticulate covering; whereas, wild garlic has a membrane covered bulb.

Control in wheat:
Since control measures in wheat differ for wild onion and wild garlic, producers consultants and industry personnel will want to make certain that they are able to distinguish between these two weed species. Harmony Extra (thifensulfuron + tribenuron) is the herbicide most commonly used for control of garlic in wheat, plus it controls a relatively wide spectrum of other broadleaf weeds and possesses a fairly wide application window. Harmony GT (thifensulfuron) also has activity on wild garlic, but is considered to be slightly weaker than Harmony Extra. Peak is also labeled and effective on wild garlic in wheat, but it is fairly persistent in soil. The Peak label does not allow one to plant double crop soybean following wheat harvest in Indiana. Wild onion is controlled with 2,4-D. Keep in mind that both of these weeds are perennials and the full-labeled rate is needed for adequate control.

Control in lawns:
Since these weeds are more of a problem in poorly drained lawns and thin turf areas, control begins by maintaining a dense, healthy turf stand through good cultural practices including proper mowing height and frequency, as well as proper fertility with emphasis on fall nitrogen. More information on mowing and fertility can be found in AY-8 and AY-22.

Chemical control of onion and garlic is difficult and may not provide the expected results. Although these weeds appear grass-like, control can be attempted with post emergent broadleaf herbicides. But, while most broadleaf weeds such as dandelion are best controlled in mid to late fall, applications of herbicides containing 2,4-D, MCPP, dicamba, clopyralid, or triclopyr should be applied for onion and garlic during early to mid spring. And unlike most other broadleaf weeds, mowing immediately before the herbicide application may improve uptake and control. Be sure to carefully follow label directions. For additional broadleaf control information refer to AY-9 “Control of Broadleaf Weeds in Home lawns”.

Click on the small image to view a larger image.

Wild onion in the landscape
Photo by Glenn Hardebeck

Wild garlic infesting a field
Close up of wild onion
Photo by Glenn Hardebeck

Wild garlic
Photo by Fred Fishel,
University of Missouri – Columbia

Wild onion with flower
Wild garlic flower

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Last updated: 10 March 2003/amd
The Plant & Pest Diagnostic Laboratory at Purdue University