Nature abhors a vacuum, and weeds show up to fill in bare, disturbed soil with opportunistic plants.
If you want to control weeds and grasses, Emma Erler, host of Homegrown NH, says to try an alternative to the once widely-used herbicide glyphosate, known as RoundUp.
Glyphosate is a broad-spectrum herbicide that kills any plant it touches, and once it is absorbed through the leaves it travels to the roots, ensuring the plant won’t re-bloom. But studies have found concerns about glyphosate related to cancer, organ damage, and harm to the environment.
Erler has some suggestions for an organic herbicide to consider and, of course, there’s good old-fashioned hand-weeding.
“Organic herbicides are known as ‘burn-down’ products,” she says. “This means they are effective at killing any green, vegetative plant material they come in contact with, whether they are weeds or desirable plants.” They do not systemically move through the plant to kill the roots like glyphosate.
They work best when targeting small plants, especially annual weeds. Mature or perennial weed roots will likely survive application and will push up new leaves requiring subsequent sprays. Often, multiple applications every two to three weeks are needed for complete control.
Horticultural Vinegar
Erler says horticultural vinegar is the most readily available organic herbicide for the home gardener. It is most helpful controlling weeds in gravel or paved pathways in the garden.
How it works: Horticultural vinegar is 20-30% acetic acid, compared to vinegar for home use which is 5% acetic acid. It is effective at killing annual weeds, but doesn’t do much against perennial or well-established larger weeds. It is most effective in bright sunlight and hot weather (approximately 75 degrees and above).
Benefits: Horticultural vinegar breaks down quickly in the soil and is therefore not likely to accumulate enough to affect soil pH long-term. Repeated applications may work to control some difficult weeds.
Drawbacks: Horticultural vinegar doesn’t do much against perennial or well-established larger weeds and will damage any plant that it comes in contact with. Erler says for larger weeds, try blocking the sunlight and smothering the weeds, using layers of cardboard, newspaper, or heavy tarps.
Note: Wear gloves and eye protection when applying. Use with a hand or pump sprayer as horticultural vinegar can be hazardous to the skin and eyes.
See you in the garden!
If you have a gardening question for Homegrown NH, email or send a voice memo to HomegrownNH@NHPR.org.
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
