Be careful what you wish for

          One gardener’s ideal plant is another gardener’s nightmare. 

          More times than I’d like to admit, I’ve planted what I thought would be a useful groundcover and found it taking over. Two examples are sweet woodruff, Galium odoratum, and smooth Solomon’s seal, Polygonatum biflorum. I planted them because my yard is shady, and they promised to thrive in shade.  Thrive they did.  Smooth Solomon’s seal is native to the eastern US. I found it quite pretty, with its arching stems and modest white flowers hanging below shiny leaves.  

Smooth Solomon's seal

 Perhaps its description as “rhizomatous” should have warned me. Actually I didn’t do any research, just scooped it up from the shade plant section at a local garden center. At first its spreading pleased me, and I gave away divisions to neighbors. Pretty soon I realized it was popping up all over the garden. 

            Sweet woodruff, a European import, took longer to start to move. The little plants looked so delicate when I bought them from a mail order nursery that I wondered if they’d survive. The whorls of little pale green leaves were adorable, and that May I was delighted with the starry white flowers held above the foliage. 

Sweet woodruff

 Later I found a warning that sweet woodruff could be aggressive in the right growing environment. For years it spread gradually, until suddenly I looked up and realized it had taken off in all directions. 

          That’s the catch.  Something about my yard in particular makes an ideal home for smooth Solomon’s seal and sweet woodruff, but a few houses down, they might be well-behaved, useful groundcovers for shade. You can’t always know from other people’s experience, and it can take years before a seemingly innocent little thing shows its colors. Conservation biology confirms this phenomenon: a species has to build a colony of significant size before its population suddenly surges. It’s one reason we get suckered by exciting new imports.

          But let’s face it, the whole groundcover idea involves playing with fire. We’re looking for a plant that spreads willingly, but we also think it should stop when we want it to. Vigor is good, until it shades over into aggression. Invasiveness is really a spectrum, not a bright line.

        If I’m lucky, I’ll end up with a varied tapestry of groundcovers with different leaf forms, colors and textures. If I’m unlucky or inattentive, I’m likely to cover my whole garden with one of the strongest growers, which will look boring and be very frustrating to try to change. I tend to feel superior when I walk by neighboring front yards where shrubs are surrounded by oceans of mulch where nothing grows. What a wasted opportunity! And to me, it’s a sad look. But the joke could be on me—in twenty years, their shrubs may have widened enough to touch shoulders, while I’ll be trying to dig ever-so-native smooth Solomon’s seal out of my beds.