Groundcovers for Moist Shade

I’ve heard a lot of questions lately about substitutes for the ‘old standby’ shady groundcover plants Japanese Pachysandra (Pachysandra terminalis) and Periwinkle (Vinca minor). Both of these imports have been used for generations for the shady blanket effect under trees, but for nature-friendly gardeners who want to increase biodiversity in their yards, these plants offer very little value to birds, beneficial insects and soil health. Not to mention, but they can also become invasive in moist woods where they spread out of control – read about my ongoing battle with Japanese Pachysandra.

Here are some suggestions for native groundcover plants for New England to replace the invasives:

Running Foamflower (Tiarella cordifolia) – this is my all-time favorite native New England groundcover. In early May, it’s covered with a sea of soft white gasp-inducing blooms:

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The rest of the year, its foliage forms a nice weed-suppressing mat – as long as it’s grown in moist, rich woodland-type soil. An area under deciduous trees where leaves and duff are allowed to build up in the soil is ideal.

Wild Ginger (Asarum canadense) is an essential component of New England native plant gardens as green “filler” to weave in and around larger plants – forming a living mulch that keeps the soil cool and prevents weed formation. Its dull-red flowers form in early spring – at ground-level to cater to ground-dwelling pollinating insects.

Shown below at the right of the photo, the heart-shaped leaves of wild ginger mingle beautifully with ferns and other woodland plants – remaining green and lush after the spring ephemerals are long gone:

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Another native plant that will quickly cover a moist shady area is Mayapple (Podophyllum peltatum), shown here growing under oak trees at Garden in the Woods in Framingham MA:

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Mayapple will dominate surrounding plants, so give it an area all its own where it won’t dwarf its neighbors.

Bunchberry or Creeping Dogwood (Cornus canadensis) is a native woodland plant with late-spring flowers that look like small dogwood blossoms:

bunchberry IMG_7493Bunchberry is late to fully form its foliage in the springtime, so it’s not as effective at suppressing weeds at Pachysandra, but if grown in a cool, damp soil, it will happily spreads into large patches that can be occasionally mowed to keep other weeds at bay.

Last but not least, did you know there is a Pachysandra native to the eastern US? Allegheny Spurge (Pachysandra procumbens) grows wild in rich woods from West Virginia and Kentucky south to Louisiana and Florida, but it is quite hardy in most of New England (to zone 4). It’s semi-evergreen (unlike its evergreen Asian cousin Japanese Pachysandra) with spring flowers that smell like cinnamon:

pachysandra procumbens IMG_9972In my experience, Allegheny Spurge needs consistent moisture in its first few years, but becomes quite drought-tolerant once established. It’s most happy with some summer shade in New England, and spreads nicely from clumps rather than the aggressive underground runners of the Asian variety which invade moist woods here in Massachusetts.

Native wildlife gardening purists might disagree with using a southern native in the northeast where it’s not traditionally indigenous, but as average temperatures continue to rise in the coming decades, we may find that growing southern species here in New England will support their co-adapted pollinators and other specialized insects as they migrate north in an effort to survive. As we struggle to maintain biodiversity in an era of mass species extinctions, these kinds of assisted migrations may become essential…

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