I am trying to expand my “lawnfree” garden area about 10’. I don’t want to use herbicides - not due to any chemical concerns so much as not wanting to inadvertently damage anything. So I am thinking of sheet mulching (cardboard or paper with something over top) instead. However, I know significant root mass from several trees and bramble plants extends into the area in question. Would I risk notable root damage (from blocking out water and some percentage of oxygen for at least a few months) by doing this?
You’re good to go, no worries. Your established tree roots should be deep enough to tap into some deep moisture and nutrients. There is moisture mere inches or feet under most building foundations and they block out much larger space than what you are concerned about.
I’ve never noticed any issues…i’ve used heavy cardboard covered with woodchips many many times. It breaks down quickly though. Worms love that it.
I was surprised how quickly it works. I laid out a new bed the last week of March. Cardboard, compost, then mulch. Last Friday I dug a hole to plant a new tree, and the cardboard was almost gone and grass was almost dead. I thought it would need 6 months, not 6 weeks.
I hate having a useless lawn. It doesn’t feed me and only costs me time and money to manage. I’m working on a sheet mulched setting for most of my yard in the near future. I’m sandwiching gooseberries, currants, salal, and similar smaller fruit baring shrubs between them. My next plan is to put false solomon’s seal, mahonia, and strawberries between that. At that rate even with periodical mulching I shouldn’t have grass.