There is a “growing” trend toward using groundcovers to reduce the need for bark mulch in gardens. As with any trend, there is a time and place where it is appropriate, and other times when it is not. One plant that we absolutely love for that purpose is the evergreen Carex flacca ‘Mini’. This blue-foliaged sedge is a Mediterranean native marsh grass that spreads very slowly, so it is not a problem in overrunning other plants in the bed, as long as they aren’t placed too close. These pictured below were planted six years ago on 1′ centers, and are just now knitting together.
We have studied a few reports of this sedge being invasive in parts of the northeast US, but our trials have shown quite the opposite, with nary a seedling in over six years. We can find no scientific research that shows this sedge qualifies as being invasive using any commonly recognized definitions of an invasive plant. Our skepticism of these reports comes because some of the ridiculous listings that appear on invasive species lists, which have no scientific basis. Our favorite invasive faux pas was a listing a couple of years ago of the genus Bambusa on a state invasive list. Never mind the plant is a strict clumper and only flowers once every 100 years. Winter hardiness is Zone 4-9.