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While one gardener’s weed is another’s salad, most everyone will agree that uninvited plants simply get in the way of what we want to grow. Here are profiles of 12 of the most common culprits to help you identify these unannounced guests.
Dandelion
Taraxacum officinale
Perennial; spreads by seeds; height to 1 foot; found in U.S. (not southernmost TX, CA, AZ, and FL) and southern Canada; can flower at any time when temperatures permit.
Dig out the entire taproot, hoe plants before they flower, and spread corn gluten in early spring to suppress seedlings.
Harvest young leaves for tender green salad.
Photo: (cc) Anders Sandberg/Flickr
Annual Sowthistle
Sonchus oleraceus
Perennial; spreads by seeds; height to 18 inches; found across U.S. and southern Canada, mostly in lawns; flowers July through October.
Dig out entire root, or cut at soil line until root stops sprouting. Aerate and add organic matter to lawn. This weed tolerates compacted soil and shade.
Photo: (cc) Phil Sellens/Flickr
Carpetweed
Mollugo verticillata
Annual; spreads by seeds; stems grow to 1 foot; found across U.S., except for ND and parts of MT and MN; flowers June through November.
Hoe or pull plants when they appear. Mulch deeply to smother any seedlings.
Photo: (cc) Robert H. Mohlenbrock/USDA
Large Crabgrass
Digitaria sanguinalis
Annual; spreads by seeds/roots at leaf joints; height to 3 feet; found across U.S., except ND and parts of SD, MT, and MN; flowers June through October.
Pull out entire plant, including roots. Mulch or let grass grow to 3 to 4 inches high to prevent seed germination. Mowing will not kill this plant. Spread corn gluten in early spring to suppress seedlings.
Photo: Rodale
Poison Ivy
Rhus radicans
Perennial; spreads by creeping rootstock; found across U.S. (not AK or CA) and southern Canada, as vine or shrub; flowers in May and June.
Entire plant is toxic. Wear protective gloves and clothing. Cut plant at base, let it dry out, and bury or put vines in trash. Do not compost or burn (inhaling smoke can be fatal). Mulch with cardboard.
Photo: (cc) H. Spauldi/Flickr
Prickly Lettuce
Lactuca serriola
Annual/biennial; spreads by seeds; height to 5 feet; found across U.S. except southernmost Florida; flowers July through September.
Hoe or pull plants as you see them, or cut taproot below soil line. Wear gloves. Attracts beneficial insects and so may be fine for outlying areas, but can play host to lettuce diseases.
Photo: US Geological Survey USGS/Ft. Collins, CO
Common Cocklebur
Xanthium strumarium
Annual; spreads by seeds; height to 4 feet; found across U.S. and most of southern Canada, except Quebec and northern New England; flowers August through October.
Pull or hoe plants beneath soil line. Can be composted if haven’t gone to seed. Use dense mulch to smother seedlings. Thrives in wet soil. Poisonous to livestock; often confused with common burdock.
Photo: (cc) Joshua Mayer/Flickr
Canada Thistle
Cirsium arvense
Perennial; spreads by seeds/rhizomes; height to 5 feet; found coast to coast across northern U.S. into Canada; flowers July through October.
Wearing gloves, dig out plants, removing as much root as possible. Cut down new shoots monthly. Mulch with cardboard. Spread corn gluten in early spring to suppress seedlings.
Photo: (cc) Matt Lavin/Flickr
Lamb’s-quarters
Chenopodium album
Annual; spreads by seeds; height to 3 feet; found across U.S.; flowers June through October.
Hoe or pull plants as you see them. Mulch seedlings heavily. Leaves are edible.
Photo: (cc) Franken Stoen/Flickr
Read More: Weeds You Can Eat!
Common Ragweed
Ambrosia artemisiifolia
Annual; spreads by seeds; height to 3 feet; found across U.S. (not northern ME, WI, or MN) and central and eastern Canada; flowers July through October.
Hoe seedlings and mow larger plants. Mulch or plant cover crops on fallow areas. Plants can be composted if haven’t gone to seed. The pollen is a common cause of hay fever and allergies.
Photo: (cc) Frank Mayfield/Flickr
Common Purslane
Portulaca oleracea
Annual; spreads by seeds and rerooting; stems grow to 10 to 14 inches; found across U.S. and southern Canada; flowers August through October.
Hoe and remove plants. Pulled plants will reroot if left on top of soil. Seeds can mature after plant has been pulled. Smother seedlings with a deep mulch. Plant is edible.
Photo: (cc) Jason Hollinger/Flickr
Learn More: 8 Weeds You Can Eat.
Redroot Pigweed
Amaranthus retroflexus
Annual; spreads by seeds; height to 6 feet; found across U.S. and southern Canada; flowers July through November.
Till beds a week before planting to allow seedlings to sprout, then hoe them under, and mulch deeply. Pulled plants can reroot. Late summer and early fall seedlings can set seed when only a few inches tall.
Photo: (cc) Matt Lavin/Flickr
