I have a quarter circle garden in my front yard with one side against
my driveway and the other against the sidewalk. It contains white
rocks with a little juniper bush in the center. This garden is always
full of weeds and I'm not the type to do the work needed to keep it
weed free.

Last time I was fed up, I removed the rocks from the garden and then
laid down black matting which is supposed to block weeds. On top of
that I put mulch and then added white rocks on top. All that work did
not prevent weeds.

My thought this time is to remove the rocks and mulch and pour in
concrete - maybe 2 inches thick. Then I can put the white rocks on
top without the mulch.

I am concerned for the plant in the center. I will want to leave a
hole for the plant. My concern is that the plant would be starved if
I don't make the hole big enough. Would the plant do fine as long as
its root system can dig down under the plant or would I need to give
it some breathing room?