Garden News Blog

Groundcovers for Tree Beds

Mulch in street tree beds is a wonderful thing—a two- or three-inch layer of untreated wood chips placed about eight inches away from the trunk serves to protect soil, hold moisture, and suppress weeds. Yet living mulches—creeping or short-growing plants, also known as groundcovers—do all that too, and also reward you with a carpet of green and sometimes flowers. Once established, native groundcovers offer the added bonuses of easy care and food for native pollinators.

First, decide if your street tree is a good candidate for companions. Not enough soil for planting? You should absolutely never add soil to a street tree bed, so if in doubt, don’t plant. Before planting anything, determine how much sunlight reaches the bed and choose plants accordingly. Use small, young plants or plugs to cause as little disturbance as possible to the tree’s roots during planting. Space them so that when full grown, they will touch to create a blanket of foliage.

Here are a few native perennial groundcovers to try:

For Dry Shade

  • Christmas fern (Polystichum acrostichoides)
  • Coral bells (Heuchera americana)
  • Foam flower (Tiarella cordifolia)
  • Oak sedge (Carex pensylvanica)
  • Wild geranium (Geranium maculatum)

For Dry Sun

  • Blue-eyed grass (Sisyrinchium angustifolium ‘Lucerne’)
  • Creeping phlox (Phlox subulata)
  • Oak sedge (Carex pensylvanica)
  • Prickly-pear cactus (Opuntia humifusa)
  • Wild petunia (Ruellia humilis)

Remember, these plants are low maintenance, not no maintenance. Gently water the bed thoroughly and regularly for the first year or two. And remember, your street tree needs at least 20 gallons of water weekly, March through December. Every spring, add a thin layer of compost around your plants. In early winter, consider covering the bed lightly with evergreen branches to protect the soil and plants from winter salt spray.

Mulching your street tree is good stewardship, and using living mulch will bring your tree bed garden’s beauty to a whole new level!

Want to learn more? Register for a community greening workshop.

Maureen O’Brien is the community field manager at Brooklyn Botanic Garden.

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Image, top of page:
Wild Geranium
Geranium maculatum (wild geranium). Photo by Sarah Schmidt.
Oak Sedge
Carex pensylvanica (oak sedge) in the Water Garden. Photo by Alvina Lai.