Try landscape fabric. It blocks a lot of weeds and makes pulling the
others easier. However, manufacturers recommend you cover the fabric
with X inches (cm) of mulch.

As for using herbicides, I never had to do it, so I don't know. (Have
had landscape fabric installed 2-3 years now).

Actually, I had already had landscape fabric installed before I put
mulch. As I said, it helps in the first one or two years. Now, four
years later, I find that the following things makes it increasing less
effective in blocking weeds:

- I like to plant new stuffs (such as annuals). Therefore, I keep
digging through the landscape fabrics; this not only making holes on
the landscape fabrics, but also causing soil to be spreaded on top of
the mulch and got all mixed together.

- As mentioned previously, the mulch has decomposed significantly and
become more like soil than mulch.

Moreover, I become less and less like to use landscape fabrics (and
mulch) because it prevents me from easily adding fertilizer or other
goodies directly to the soil. Seem like the only way to add fertilizer
is using liquid fertilizer.

Thanks.

Jay Chan