Here's the rub: weed killers - herbicides - can't distinguish between a weed or any other sort of plant, many of which are desirable in the garden. At most, they will target specific plant types but not necessarily individual plants. Weed killers used on lawns typically target boadleaved weeds, leaving the turf grass/lawn alone. Using the same weed killer in a planted area with flowering plants, annuals, perennials etc. runs the risk of killing those plants as well, as the herbicide only recognizes them as broadleaved.

Using any sort of herbicide in a non-lawn planted area is risky. Really only the ones that target monocots or grass-like (single bladed) plants are safe. Your options are to remove any weeds in these areas manually, burn them off individually (and very carefully) with a weed torch or smother them.

Once the weeds are removed, mulching will help to keep them under control but nothing will keep them out forever.

The plants are less of a concern. I could probably live with killing them as long as it didn't kill my citrus trees.

It's impossible to pull the weeds because a grass type weed just takes over. I'd be in there 30 minutes every day.

don't understand your goal..don't mind killing plants leaving citrus trees and bare dirt?..

You need to identify the grass-type weed. Some will be very responsive to a herbicide like Grass-B-Gon while others - nutsedge in particular comes to mind - will just laugh at it.

There are very effective sedge killers but so expensive, I use them on areas too large for manual removal. Still need to ID offending weed b4 going spray-happy.

OP - Would you post pic(s) of your grassy weeds? The experts (not I!) might be able to help ID for you.

ETA: In the early days of home ownership, I wished I spent only 30 min/day weeding. It took me months to get ahead of it all, but decades later, the management isn't bad at all. Per gardengal, once the weeds are gone, mulch, mulch, mulch!

Thanks everyone. It turns out that the grassy weeds infact weren't weeds at all. It was Bermuda grass taking over.

I don't mind not having flowers because I think the trees look good surrounded by mulch.

Some people consider bermuda highly undesirable in gardens. Also they can obliterate other kind of lawn grasses. If this is not a concern, then growing around trees is ok. There are killers specifically for Bermuda, FYI.

You're going to need a hard barrier around the mulch area to keep creeping grass from creeping back in. If you cover the area with corrugated cardboard, overlapping the seams well, then cover with the mulch, that should eliminate anything growing up from underneath.

But if what is underneath is any kind of rhizomatous grass, you will also need to sever all ties between grass under the mulch and grass outside the mulch, by cutting all the way around the mulch area with a shovel. Replenish the mulch as needed and then you will only have whatever sprouts in the mulch to deal with, as far as sprouts go. When you mow around the mulched area, aim the chute away, so you're not slinging grass seed back into it.

grasses like Bermuda & st Augustine & weeds like creeping Charlie will grow like a mat right over your mulch. I had sometime 1/16" steel strips leftover from a bridge job that I buried 8" deep along a short strip of property line tp keep my neighbor's zoysia from invading my yard.