Star Gardener: Groundcover: Blessing or Curse?

Mortal combat
Last year, the author extolled the virtues of groundcover plants, left. This year, right, it’s a different story. Are they a blessing or a curse? Abby Jane Brody Photos

Was it only last summer when I was extolling the virtues of groundcovers, illustrating them (the virtues) with an image of a handsome mosaic of shade-loving, textured greens? Sweet woodruff, a variegated carex, and wild strawberry, a gift from Jacques Peltier of a plant from the French village where his mother lived. That was last year.

This year it’s a different story.  The sweet woodruff and the strawberry originally were planted away from each other. Now they are engaged in mortal combat, and it is easy to see the strawberry will win. In just one season the two have engulfed two young plants of false holly, osmanthus.  

It becomes a question, then, whether groundcovers are a blessing or a curse. Why groundcovers, in the first place?  Functionally, they can do an outstanding job of reducing weeds, and they are good for erosion control on slopes. Aesthetically, they provide an attractive carpet, especially under trees and shrubs. (Some people cannot abide the sight of bare ground.) More important for me, they can pull a disparate grouping of plants into a harmonious unit. Undoubtedly, they are more attractive than the large beds of mulch we see on properties throughout town.

However, they tend to be planted and then promptly forgotten, and that can be a huge mistake. English ivy has been known to fell large trees. Pachysandra spreads by rhizomes that are nearly impossible to eradicate.  Vinca is so difficult to dislodge I had to ask someone stronger than I to do it. When an area at the Mimi Meehan Native Plant Garden at Clinton Academy was finally cleared, trilliums and May apples that had been smothered for decades returned. Today there are good-sized colonies of trillium, and the May apples have now become invasive.

These most robust of the groundcovers may not be eaten by deer, but they do make good homes for all sorts of rodents. (This year there has been a sharp upward spike in the mole/vole/chipmunk population.) Even the most obliging and benign of groundcovers are like hot lava flowing inexorably downhill, covering everything in their wake. What you, or I, thought would solve our weeding problem and reduce maintenance could become a curse, causing more problems than the weeds.

The moral, if there is one, is to be careful which groundcovers you select, and then remember to schedule regular maintenance to keep them within bounds.  

Recently I’ve been pulling out yards of sweet woodruff. Fortunately its roots run just below the surface and plants are easily removed without damaging the roots of the trees and shrubs above. This works if you don’t mind getting on your belly and wriggling to get under shrubs to reach it.  

Other groundcovers are not so easy to remove. We all love lily of the valley, don’t we? That is, until it needs to be contained. Even my largest and strongest trowel couldn’t reach down to the rhizomes that grow under Japanese maples and shallow rooted azaleas.

What are the possibilities without resorting to monocultures of groundcovers that are difficult to control? Among the many that are easy to contain, or pull out, are ajuga, geranium macrorrhizum (big root geranium), clump-forming carexes, woodrushes, ornamental fescues, some of the gingers, lamium, woodland phlox, chrysogonum, and Kenilworth ivy. Most do well in sun to partial shade.  

  I particularly like tapestries of compatible plants that flower at different times and with different foliage textures. In the native plant garden I’m mixing the low-growing, spreading, but easily moved or removed foamflower, Tiarella Brandywine, with clump-forming Christmas ferns, woodrushes (Luzula acuminata), heucheras, crested iris, and gingers. In another year or two we’ll see if they knit together well.

In my home garden, where I can use plants from Asia and Europe as well as natives, combinations of hellebores, epimedium, pulmonaria, and clump-forming ferns pull the woodland plantings together. In other areas, masses of woodland phlox are gorgeous when they flower in early May and are succeeded by hostas, growing cheek by jowl. What is not so gorgeous is that grass and other weeds have established themselves under the phlox and are impossible to eradicate.

What this means, I suppose, is either we are out in the garden maintaining our groundcovers, or we take our chances, live with the consequences, or try again.