Answer: Aside from hand pulling the weeds-or grass there are a few possibilities. Applying plastic mulch would be the first one. However, that would probably be quite difficult at this point.
You could put a heavy organic mulch on it however. I'm sure with a bit of "shaking and rattling" you could work it into and under the juniper. After a few rains (or hosings) it would probably look OK. Before you attempt this, you MUST weed out the grass by hand, or it will just grow through the mulch. You could do a section at a time so it's not too exhausting or discouraging.
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