Invasion of Redroot Pigweed - Ask Extension
My lawn has been invaded by redroot pigweed. I have been pulling it since spring, but with the drought, it has flourished. I have a dog, and it is poi...
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Invasion of Redroot Pigweed #942756
Asked August 18, 2026, 10:30 AM EDT
My lawn has been invaded by redroot pigweed. I have been pulling it since spring, but with the drought, it has flourished. I have a dog, and it is poisonous to pets. I want to get rid of it before it takes over my whole yard. Can you suggest a safe herbicide to use? It is an annual, so I could use a preemergent herbicide next spring. I overseed the lawn every fall and in March.
Larimer County Colorado
Expert Response
Hi Anthony,
Can you send me a close up photo of the weed? It looks more like purslane than pigweed, but I want to be sure.
The problem with treating either of these weeds now is that it's a summer annual and will die with the first frost, which could be in just a few weeks. Plus, the maturity of these plants make them very resistant to any herbicides.
You'll notice how it's only growing in the space where there isn't turf competition, so that's step #1. You must introduce competition - it will not invade the turf area because it's not competitive enough.
Once we confirm the weed ID, then we can talk about preemergence herbicides and seeding. Feel free to email me directly: <personal data hidden>
Can you send me a close up photo of the weed? It looks more like purslane than pigweed, but I want to be sure.
The problem with treating either of these weeds now is that it's a summer annual and will die with the first frost, which could be in just a few weeks. Plus, the maturity of these plants make them very resistant to any herbicides.
You'll notice how it's only growing in the space where there isn't turf competition, so that's step #1. You must introduce competition - it will not invade the turf area because it's not competitive enough.
Once we confirm the weed ID, then we can talk about preemergence herbicides and seeding. Feel free to email me directly: <personal data hidden>
