Evergreen ground covers are one of the most sought-after lists of plants – particularly for shade areas.
Many plants simply don’t qualify as “ground covers” because they don’t spread very well, aren’t short enough to be considered “covers” (under 24-inches and preferably under 12-inches) and/or are not dense enough to even begin to inhibit weed growth underneath them.
Here’s the real deal here. If you want a true, evergreen ground cover in a USDA zone 4, then your choices are limited to a very few plants. And most of them are not considered perennials, but rather woody plants.
Juniper – creeping varieties will hold their “green” foliage year round with little fuss and muss. They thrive in full sun and are not plants for shade. These are not perennial but woody evergreen plants.
Cotoneaster these are woody plants, are excellent and do hold their leaves. Get the spreading forms but not the upright ones.
English Ivy will hold leaves under snow cover in USDA 4 (the variety ‘Baltic’ is the hardiest) but frankly, once that snow cover goes, so do the leaves and often the entire plant. You need to be into at least a USDA 5 to grow this plant without losing it every year (microclimates in 4 can do so) In areas where it is hardy, it can quickly become noxious.
Pachysandra will stay evergreen in USDA 4 but will appear limp and somewhat ugly. Snow cover is again it’s best friend. Slow spreader.
Vinca tends to drop leaves in USDA 4 although it will develop new ones quickly. Better in areas with reliable snowcover – lack of snow turns the leaves interesting shades of dead-brown. One of the best choices for shade, spreading fast and low-maintenance.
Arabis and Aubretia are both considered tough evergreen plants in well-drained soils (like alpine gardens) although they will both center-die and the adults will die out behind the new growth requiring a yearly maintenance.
Sedums (creeping forms) are “evergreen” in that the leaves tend to stay on the plants but they’re not overly attractive in winter (at least not in my opinion) A tough, snowless winter will knock the leaves off them in USDA 4 but they will recover if not overwatered.
Thymus species are great in warmer areas but drop their leaves in USDA 4.
Phlox subulata goes a lovely shade of brown-green and then greens right up in spring (does better when fully snow covered in USDA 4 although it may develop some center dieback and fungal problems under the snow)
So there are the few plants that will/might survive as an evergreen ground cover in a USDA zone 4. I note that if you live in warmer areas, then these are more likely to be evergreen for you and the range of plants starts to increase.
Sedum kamchatiscum variegata