What would you put in the strip by the fence?

For the longest-lasting low-maintenance option, I’d make it a narrow hardscape strip rather than try to keep mulch or fabric weed-free. Small concrete pavers or larger flat stones can sit between the sidewalk and fence, with a compacted base underneath. Set the finished surface so it’s easy to mow or edge alongside, and avoid trapping soil or water against the fence.

Before digging, check where the fence posts are and whether there are any clearance rules for the sidewalk. A tidy, straight edge can also make it easier to stop the strip cleanly at the end of the fence.

If you don’t want a visible band of stone or paving, keeping grass there may actually be the simplest. A mower and a careful pass with an edger can be less fuss than managing loose rock, weeds in fabric, or plants that spread onto the sidewalk.

If you want to stop the trimmer from touching the fence, a thin, sturdy edging strip right along the fence could help. Just make sure it’s installed securely and doesn’t create a sharp or raised edge where people walk.

A narrow planting strip can work if you’re open to a bit of gardening. Choose compact, upright plants suited to the sun and local conditions, and leave enough room that they won’t flop over the sidewalk. Dense ground cover may reduce open soil, but it won’t mean zero weeding.

I’d skip loose river rock in such a tight spot. It can scatter onto the walk, and weeds can still grow through it. Check any appearance rules before planting if that’s a concern.

One practical middle ground is to lay a slim row of pavers or brick along the fence and keep the rest as grass. It gives the trimmer a buffer without turning the whole gap into a garden feature. For a clean stop, end the row square with the fence, or use a matching end piece rather than tapering it awkwardly.

The base and fit matter more than weed fabric here. If pavers shift or leave wide joints, weeds will find a way in, so keep the joints tight and expect occasional cleanup.