The Worst Invasive Plants and Garden Weeds

Our list of worst invasive plants and garden weeds will have you covered for the summer gardening season.

  • Purple Loosestrife
    Purple Loosestrife is an invasive weed. Nehring
  • Canada Thistle
    Canada thistle is a hardy perennial weed. H. Smith
  • Bindweed
    Bindweed is tough to kill. Whiteway
  • Marsh Dodder
    Dodder spreads like wildfire. Dicks

  • Purple Loosestrife
  • Canada Thistle
  • Bindweed
  • Marsh Dodder

They’re the schoolyard bullies of the plant world – bigger, meaner and pushier than anything else in the garden. They’re frequently the first to show up in spring. They compete relentlessly for soil nutrients, moisture and growing space intended for your crop. And they’ll fight back if you try to subdue them. You can hoe ’em, pull ’em out by the roots, smother ’em with compost, or spray ’em with chemicals, but these invasive plants and garden weeds just keep coming back.

Of the thousands of weed species inhabiting North America, here are 10 of the meanest you’ll encounter.

Most menacing. Found in all 48 contiguous states and Hawaii, dodder is a parasitic plant with yellow or reddish filaments that wrap themselves around flowers such as salvia, petunias, mums and geraniums, and garden plants including potatoes, onions and blueberries. Also known as strangleweed, devil’s guts and hairweed, dodder uses suckers to draw water and nutrients from the host plant. As it continues to spread from host to host, it flowers and sets seeds. As soon as each seed germinates, it begins searching for a host plant, and the process continues. If dodder gains a foothold in your garden, you may have to cut the affected plants down to the ground, collect and burn them.

Hardest to kill. Forget hoeing out a bindweed infestation. Even a fragment of a remaining root or rhizome is capable of regenerating a new plant. Because a single plant can produce up to 200 vertical roots that may grow as much as 30 feet deep, you’d need a backhoe to get ’em all. You can try smothering a bind-
weed patch with plastic sheeting, but some gardeners
report vines that have run as far as 40 feet under landscape fabric and mulch to emerge in the sunlight. Intense tillage a few days after each emergence helps, but since the seeds remain viable in the soil for up to 50 years, you may have to till your garden continuously for two or more years to bring it under control.

Fastest growing. The fastest growing weed may be kudzu, called the “foot-a-night vine” because it literally can grow a foot each day. Imported from Japan in 1876, this vine infests more than 7 million acres throughout the Southeast United States, and has even been found in the Pacific Northwest. It’s known to kill trees, destroy forests, pull down power lines and overwhelm houses. Agronomists say it can take seven to 10 years of repeated herbicide use and cutting and chopping to subdue an infestation.

Most prolific. The champion could well be the purple loosestrife, with each plant capable of producing 2 to 3 million seeds annually. Introduced to the United States from Europe in the 1800s for ornamental and medical uses, the purple loosestrife has invaded wetlands, crop fields and pastures in virtually every contiguous state in the nation.

6/11/2019 3:12:41 PM

Sally Johnson there is a weed book out that is called "Weeds of the West". It may help you, cuz it has actual photos of the weeds. Hope this helps.

7/31/2011 11:13:03 AM

The solution for purslane? Eat it!

Carol Wingert
5/20/2011 10:16:48 PM

I learned the hard way about another "invasive" plant - the Jerusalem Artichoke. The flowers are beautiful, and the roots are delicious to eat, but in order to get a "nice size" root, you have to cut back some of the buds before they flower AND don't plant them too close together (like we did) I knew the "roots" spread, but didn't realize how fast and how much! They took over my 4 x 8 raised bed! Although I've dug out almost 80 roots (giving much away) I still have many to harvest and transplant.

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