Hi, I have many perrenials in my yard and want to remove grass and weed completely. My understanding is the safest way is to cover the yard with newspaper and mulch for winter time. The question is, do I cover over the perrenials as well including tulip bulbs or not? Do I remove the mulch next year before perrenials start to grow back? Btw, I live in Toronto.
You’re right, covering the grass with thick layers of newspaper (about 10 sheets thick) or corrugated cardboard (single sheets) and covering this with soil/mulch is a good way to replace your lawn. This is called sheet mulching, sheet composting or lasagna composting. The sheets act as barriers to smother whatever is under them – here, the lawn. If you sheet mulch before the first autumn frost, the garden area should be ready by next spring for gardening — although it may take longer. Generally, the process should take 4-6 months, but some resources indicate that it might take up to a year.
Here are the recommended steps:
- Dig a small trench to create a barrier around the border of the area you are sheet mulching.
- Remove tall weeds and invasive plants. The paper barrier may not smother these bad guys.
- Mow the grass as short as you can.
- Water the area well.
- Choose a paper barrier – newspaper or cardboard. There are some concerns about using cardboard, which may attract termites. See Ask a Master Gardener. Cardboard as weed barrier and termites.
- Put the paper barrier in place and let each piece overlap the other by around 15 cm (6 inches) – like shingles, so there are no holes or gaps in the barrier. If you use cardboard, use pieces with a minimum of ink, and remove staples/tape.
- Press the edges of the barrier into the trench so it will remain in place. This will prevent weeds from sneaking up between pieces.
- If the sheeting is near existing plants, keep the paper a good distance from the plant stems – ideally around 30 cm (1 foot) distant, farther if the plants spread via underground stems. This also applies to trees – remember to keep the paper/mulch away from trunks, which require good air circulation.
- Water the area well again.
- If you wish, add about 2.5 cm (1 inch) of compost on top of the barrier, to help enrich the soil underneath. Finally, add around 15 cm (6 inches) of mulch on top of the barrier – you can use straw, grass clippings, wood chips or bark.
- Water the area a final time, then about once a week during dry weather. The area should not be allowed to dry out.
- The paper will break down into the soil, do not remove any of the remaining mulch – just leave it in place.
As for your existing plants – if the perennials and bulbs are located close to but not within the lawn area, you would not need to cover these. However, for perennials that are growing within the current lawn space, cut through the paper to make a hole that will allow the plants to grow through the sheeting, giving the stems lots of room, as indicated above. As for the tulips, if you remember where the bulbs are located (I usually don’t!), it is recommended to keep that area free of paper as well, as the amount of paper/mulch used for sheet mulching would likely adversely affect the bulbs. However, consider covering the bare soil in those spots with about 5-10 cm (2-4 inches) of mulch. This will help to keep down the weeds and will allow the bulbs to easily push through come spring. Anticipate that weeds and stray tufts of grass may also grow up through any gaps in the sheeting.
Don’t plant any annual plants at this time (it is late September, we’re heading into winter!). However, if you can’t wait until spring, you can go ahead and plant trees, shrubs and hardy perennials in the soil now. Make a small “x” cut through the paper and pop in the bulbs or plants. As noted above, make sure there is good space between the paper/mulch and the plant stems. Also, as mentioned above, add 5-10 cm (2-4 inches) of mulch to cover the spots where you plant bulbs. Any holes in the paper and the thinner mulch layer could let nasty weeds grow through, so be prepared!
There are lots of online resources that provide lots of helpful details about sheet mulching. For example, see the following:
- Oregon State University Extension. Sheet mulching — aka lasagna composting — builds soil, saves time.
- University of California, Div. of Agriculture and Natural Resources. Sheet mulching.
- University of California, Div. of Agriculture and Natural Resources. Sheet mulching with cardboard – do’s and don’ts. (this also is of interest if you will be using newspaper)
Enjoy the sheet mulching process, and may your only challenge next spring be to select the ideal perennials for your lovely garden!
September 26 2022