After a weekend of chopping down Japanese knotweed, one of the more invasive plant species in North America, it’s a good time to review some tips on how to get rid of invasive plants without resorting to chemicals.
This seems to be contradictory, since many plants are mulched, but an extra layer of organic matter can smother and inhibit weeds, as well as prevent new seeds from germinating.
You can mulch with compost, bark, wood chips, newspaper, cardboard, grass clippings, or straw. It’s a good idea to avoid hay, since that can have a lot of unwanted seeds.
2. Dig them out
If you’ve got the time and energy for it, there’s nothing better than digging them out by hand. Many weeds may come back and need to be dug again, but consistent hand-weeding will greatly reduce their populations.
When young weeds are promptly dug out, they won’t be able to seed and reproduce.
3. Don’t leave room for them
If you want to avoid weeds, take up all the available space.
Try planting dense groundcovers and perennial plants in ornamental beds. The shade and heavy root systems of trees and shrubs can naturally prevent weeds from growing underneath.
4. A strict diet
As you painstakingly feed and water your plants, you’re also feeding and watering weeds.
Only give your plants what they need. Well-established trees, shrubs and perennial plants can often do well without a lot of extra fertilizer and irrigation. Vegetables may need a bit more, but you can be selective.
Solarization amounts to baking the weeds to death.
Cover an area of weeds with a heavy plastic sheet. This works best in full sun where the heat will collect under the sheet and literally bake the weeds.
Leave the sheet in place for 4 to 6 weeks. When the weeds underneath are brown and desiccated, they’re done.
6. Avoid the tiller
Instead of turning over the earth in your flower bed, try minimally disturbing the surface as you plant. Turning over the soil can bring new weed seeds to the surface.
Try the no-till method of gardening. For example, if you’re seeding vegetables, only dig down as far as you need to plant the seeds instead of deeply digging or tilling the entire bed.
The no-till method has been shown to improve soil structure and fertility, as well as increase beneficial soil organisms.
7. Spray corn gluten meal
Corn gluten meal is a byproduct of the corn milling process that’s been found to prevent weed seeds from germinating. It’s often applied to lawns, or can be used in other garden areas. It’s non-toxic to animals and you can buy certified organic corn gluten meal in stores and online.
If you want a more entertaining weeding experience, you can use a vodka spray to kill them.
Mix 1 ounce vodka, 2 cups of water, and a couple drops of dish soap and spray them on weeds with good sun exposure. This will often dry them out and kill them. It doesn’t work well in shady areas.
9. Boiling water
Simply boil a kettle of water and pour it over any undesirable weeds to burn them.
This works especially well for weeds growing in cracks of pavement or cement. The water will cool as it runs off to the sides of your pavement and won’t hurt any plants along the border.
We’re not talking about burning your weeds on a wildfire scale here. Instead, pass a flame over a weed briefly in order to fatally heat the plant tissues. You can get a flame weeder – a wand connected to a propane tank – at your local garden center or hardware store.
Flaming will only kill the weed parts above the ground, not the roots, so you may need to flame your weeds a few times before they’re gone. Do not do this when there is any hazard of starting a wildfire.