This story was originally published in June 2020.
Weeding is one of the most tedious gardening tasks, but it's a necessary task if you want a bountiful harvest. Home gardeners and professionals alike are always looking for new ways to solve the weeding woes, from adding mulch to using flame throwers on troublesome plants.
With just a little advance planning, one preventative strategy could solve your weed problem for good.
Sonia Bartisel, a postdoctoral researcher at the University of Maine, has been studying a weed control strategy that involves covering plots with reusable plastic tarps for about a week before planting. This technique, known as “tarpaulining,” is becoming increasingly popular in the horticultural community, especially among small farmers looking to control weeds effectively and efficiently.
Here's how to do it: Prepare a flat, smooth flowerbed and moisten it thoroughly (ideally right after a rainy day). Before you plant your crops in the garden plot you've prepared for spring planting, secure an opaque black or blue tarp (these dark colors are not only more common in store-bought tarps, but they also have excellent thermal conductivity) over the soil.
“You can accomplish this by either tilling in the spring and putting down a tarp, or by putting a tarp over last year's residue,” Bartisel says, “and some people find this strategy useful for a no-till gardening approach.”
Barticell said people should place bricks, sandbags or weights of some kind every few feet around the perimeter of the tarp to secure the edges and keep light out.
“What we want to do is induce lethal germination in that environment,” she explained. “When you put down the tarp, you're helping to deplete the weed seed bank that's stored in the soil.”
This process creates an “old bed” and kills weed seeds hiding beneath the soil with minimal soil disturbance and effort.
Leave the tarp in place for 7-10 days, then remove it and plant the crops or seeds directly into the field, trying to disturb as little soil as possible around the planting area.
“After you put the tarp down, you want to avoid disturbing the soil because that will bring up new weed seeds,” Barticell said.
The strategy is similar to another weed-control strategy called solarization, which uses clear plastic discarded from old greenhouses and hoop houses instead of opaque tarps.
According to Barshisel's research, solarization can have a short-term negative effect on soil biological activity. But it is effective at suppressing weeds, especially if the treatment period is short. So if you're in a hurry to plant, you might consider clear plastic sheeting. But Barshisel says solarization can be tricky to manage, or even worse, counterproductive.
“It’s really important to fill in the edges and make sure they’re secure. [or else the weeds] “It can grow very well,” Bartisel said. “I would recommend caution.”
