Several different types of plants share the common name onion weed. Plants within the Allium and Nothoscordum genera are often referred to as onion weeds, as well as a number of other names such as wild onion or wild garlic. The plant Asphodelus fistulosus also bears the onion weed moniker. In addition to sharing a common name, these plants belong to the same family -- Liliaceae or lily. They also share invasive characteristics and can be controlled in similar fashions.
The Allium genus contains hundreds of species of plants. It includes a wide variety of onions, garlic, scallions, shallots and leeks. Gardeners plant several species, such as the common garden onion, Allium cepa, specifically for their bulbs. Others, such as A. validum or A. canadense, grow on their own in the wild. These wild varieties have leaves similar to grass, growing about 2 feet tall, according to the University of Illinois at Urbana-Champaign Veterinary Medicine Library website. They produce bulbs underground which become onions. Different species of wild onion weeds grow throughout the United States, often in meadows and yards. These plants smell strongly like onions and produce small white or pink flowers.
Like wild onion, plants in the Nothoscordum genus have leaves that resemble grass. They are related to Allium plants and often times are mistaken for wild onion weeds, but Nothoscordum plants lack the strong onion scent. Several of the plants in this genus are known as false garlic, wild garlic, wild onion and onion weed. Nothoscordum plants grew natively in South America but were introduced stateside as a garden plant. These plants grow in places similar to Allium plants, such as meadows, gardens and disturbed sites. The mature Nothoscordum plant reaches around one and a half feet tall upon maturity. The plants flower in late spring to early summer, producing fragrant, bell-shaped blooms. Once the roots have been established, the plants produce underground bulbs.
The onionweed, Ashodelus fistulosus, is one of two species of plant within the Ashphodelus genus. This plant is a native of Europe, Asia and the Mediterranean. Onion weed has a similar grassy look to it as Nothoscordum and Allium plants and reaches around 2 feet tall at maturity. It is limited to areas of the country with similar warm climates, such as California and New Mexico. This plant prefers light to medium well-drained soil and commonly grows within fields, meadows, uncultivated areas and beside train tracks. Flowers bloom on the plant during the spring. The fragrant blooms are white or cream-coloured with petals arranged in a symmetrical star shape.
Controlling Onion Weed
Plants bearing the onion weed common name have invasive qualities. Several bear the label of noxious weed. The plants can cause surrounding plants in a garden to have an onion-like taste to them. Because these plants spread quickly and take over gardens easily, they aren't recommended for planting. To get rid of these weeds, the California Department of Food and Agriculture recommends frequent tilling of the land to remove seeds and bulbs, lowering the spreading of the plants. Smaller populations of onion weeds can be pulled by hand and destroyed to prevent the spreading of the seeds and bulbs. Herbicides also prove effective, but can damage nearby plants.