About 10 years ago I had a strip of THIRSTY lawn in front of my front fence that needed constant mowing, so I covered it with carpet and mulch to turn it into a parking space. But over the years weeds have sprouted in the decaying mulch, plus Nut Sedge grew up right through the carpet. I won't use conventional herbicides on the problem. But a heavy spraying of food grade potassium chloride followed by light weeding of my front carpeted driveway seems to have worked (though I still see nut sedge!). I Googled and confirmed that most red mulch is heavy in arsenic, nickel and chromate, so tomorrow I am spraying this older tree mulch with iron oxide concrete stain for a nice color contrast. Both the potassium chloride (aka muriate of potash) and the iron should be good for the roses and papayas.