I have a large area under a tree with lots of weeds. It’s been mulched in the past but the weeds have taken root and are quite plentiful now. If I cover the existing weeds with landscape fabric and plan to follow that with new mulch, do I need to wait a while before covering the fabric with mulch? Or should I cover with mulch as soon as possible?
Washington County Minnesota
Here's a suggestion:
Instead of landscape fabric, cover the area with black plastic and staple it down. This should kill the weeds after two or three weeks. I would not suggest using something like Round-Up as that may damage the tree. After two or three weeks remove the plastic. If you do not see any growing weeds, apply a pre-emergent herbicide such as Preen to prevent any weed seeds in the prior mulch from germinating. Then over this old mulch and Preen, apply your new mulch.
The problem with using landscape fabric is that it can prevent water from entering the soil. This may subsequently adversely affect your tree.