A Homegrown NH listener who identifies herself as “The Messy Gardener” wants to know how to re-establish a garden bed: “I am dealing with overgrown weeds and persistent, tall, unidentifiable flowers. I would like to clean it all out and keep only flowering shrubs and a few perennials.”
“I am dealing with overgrown weeds and persistent, tall, unidentifiable flowers. I would like to clean it all out and keep only flowering shrubs and a few perennials.”
“Outside of going through and digging everything up, which is incredibly labor intensive, I would recommend something called sheet mulching,” says Homegrown New Hampshire host Emma Erler, lead horticulturist at Squam Lakes Natural Science Center.
Sheet mulching uses cardboard, newspaper or another heavy paper material to cover the ground and suppress weeds. As the material breaks down, it also adds organic matter to the soil.
How to sheet mulch an overgrown garden
The first step is to start collecting materials. You'll need plenty of cardboard, newspaper or heavy paper to cover the entire garden bed. One important detail when using cardboard: Remove any tape and labels before putting it down.
Cut or mow weeds as close to the ground as possible to create a relatively even surface.
Lay the cardboard or newspaper in overlapping layers across the garden bed. Cover the material with clean topsoil, compost or wood chips to hold it in place and keep the garden looking tidy.
If you are hoping to keep some existing shrubs and perennials, arrange the cardboard or newspaper around the plants, covering as much of the surrounding weeds and bare soil as possible.
Over the following weeks and months, the cardboard or newspaper will break down, helping smother the plants underneath while adding organic matter to the soil.
You can plant directly through the cardboard by cutting through it even if it hasn’t broken down yet.
Sheet mulching won't keep weeds away forever, Erler says, but it can provide a fresh start for an overgrown garden.
Skip the landscape fabric
Although woven landscape fabric may seem like an attractive way to prevent weeds, Erler recommends avoiding it.
As the wood chips or mulch covering the fabric break down, weeds can germinate in that material. Their roots then grow down through the fabric, making them nearly impossible to pull.
“I would much prefer to use an organic mulching material or starting with cardboard than a more permanent plastic woven material,” Erler says.
When is the best time to sheet mulch?
For gardeners who want to preserve existing perennials, spring is the best time to get started.
“Once you know where your perennials are, once they're starting to put on their new growth, then I would be putting my cardboard down around them,” Erler says.
Waiting until plants begin emerging makes it easier to identify what you want to keep and where to place the cardboard. You can then trim or mow the surrounding weeds before covering the ground.
Starting in the fall isn't ideal because the cardboard or newspaper may break down before the weeds begin growing again in spring.
Erler's advice? Wait until spring to do the work, but start collecting cardboard. That way you have all winter to gather enough material for the project.
Homegrown NH is a collaboration between NHPR and Squam Lakes Natural Science Center.
