I was contacted by a Home Owners Association about a mulch job and I'm not sure what to do. The total area is about 12,000 sq. ft., it has 5 different beds and several of them have Purple Coneflower's, Columbine, Black-Eyed Susan, and Tall Prairie Grass. A few of the beds have nothing other than oak trees that are about 4" in diameter, these beds will be easy to do. On the other beds they want the perennials removed for maintenance reasons and then want them mulched. What is the best way to get rid of the perennials? Remove existing mulch, put down weed barrier and then put the new mulch over the top? Any suggestions on what and how to do this along with pricing would be greatly appreciated.