Planting Under Trees

What can be planted underneath a tree? Large trees often have large bare areas underneath their limbs that are virtual deserts since little, if any, rain ever penetrates the branches – especially on dense evergreen species such as Blue Spruce.  Roots often emerge from the soil making it difficult to dig.

Before considering which native plant species can be utilized in this situation, irrigation must be addressed.  Without supplemental irrigation, plants underneath an evergreen tree will not survive.  Drip systems are the most effective, especially those that coil around the base of the tree between the trunk and the outer drip lines created by the branches.  Trees have significant ground within their drip lines and it is important to plan for how big the tree will be at maturity.

drip lines

image credit:  thegoodearthgarden.com

It isn’t necessary to have your planting be circular beneath a tree!  Consider using a garden hose to lay out a pleasing shape that extends outside of the drip lines. Depending on your goals, the area beneath the tree may be incorporated into a larger landscaping area or it may be isolated as its own space.

Edging may be desired to define areas. Install edging 6 – 8 inches deep to prevent ground covers from spreading out of their boundaries.

Also consider whether or not to add soil to the area.  Often minimal soil covers heaved roots and needles have created a dense mulch that may not be easy for new plants to grow in.  Prepare soil by gently raking duff off roots and pulling any weeds. Digging the soil beneath a tree is potentially harmful to the tree.  Every root is connected to a branch and killing roots may produce visible damage to the tree as well as weakening the tree’s stability.

Add only minimal soil above the soil line.  Roots need to breathe and adding too much soil will smother some roots.  Keep the root crown at ground level and avoid piling dirt around the tree trunk.

Start with young shade plants that whose roots will find niches as they grow.  Ground covers are especially useful since their mature height stays low.  Most of the plants listed below will spread with adequate water.

Native plants appropriate for shaded areas beneath trees include:

Evergreen Groundcovers
Creeping Oregon Grape (Mahonia repens)
Kinnickinnick (Arctostaphylos uva-ursi)
Round-leaf Alumroot (Heuchera cylindrica)

also consider mosses and/or sedges (e.g. Sprengel’s Sedge)

Deciduous Groundcovers
Prairie Smoke (Geum triflorum)
Heart-Leaf Arnica (Arnica cordifolia)
Canada Violet (Viola canadensis)
Raceme Pussytoes (Antennaria racemosa)
Side-flowered Mitrewort (Mitella stauropetala)
Twinflower (Linnea borealis)
Wood Strawberry (Fragaria vesca)

So yes! you CAN plant beneath dense evergreen trees with a bit of planning and some irrigation.

 
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