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Landscape Design Around Trees

Landscape Design / October 17, 2013

Extension > Garden > SULIS > Implementation > Planting Under Existing Trees

Description/Purpose:

People are interested in under-planting existing trees for a variety of reasons. Perhaps they have struggled to keep turf grass alive under a tree canopy and are looking for a better solution. Perhaps they have a small yard and the area beneath the tree's canopy is critical to their being able to have flowerbed space in their yard. Perhaps they are tired of mowing or have admired blooming boulevards planted by others in their neighborhood and would like to follow suit. Whatever the circumstances, under planting trees with plants other than turf is an option that can be aesthetically pleasing and also beneficial to the tree, if done with certain practices and principles in mind.

Tools, Supplies and Equipment:

  • A garden fork
  • Small garden trowel
  • Garden gloves
  • Rope, a hose and / or spray paint
  • Organic mulch (shredded leaves, cocoa bean hulls, shredded bark or wood chips)
  • Slow release Nitrogen fertilizer
  • Roundup
  • A water source

    *Do not use large or power equipment, even if available!

Site Situations and Considerations:

Avoid Tree Root Damage

In all instances, care needs to be taken to minimize disturbance and damage to tree roots during the preparation and planting processes. There is a common misconception that most tree roots are deep and create a mirror image of the tree's crown. In reality, most roots are fairly close to the surface and reach even beyond the drip-line of the crown (Figures 1a and 1b). If the tree has turf growing (or struggling to grow) up to its trunk, this grass needs to be carefully removed before planting takes place. Studies have shown that young trees grown without turf beneath their canopies enjoy a more vigorous root system and grow larger and faster above ground, as well. Generous organic mulch rings under trees encourages this healthy growth. Under planting with appropriate herbaceous materials that don't compete aggressively with the tree's surface roots is also beneficial. Using either non-turf plants or mulch under trees helps keep soil from drying out quickly and eliminates thatch buildup and reduces soil compaction.

Figure 1a. Most people's imagined configuration of tree roots - sort of a mirror image of the above trunk and branch system - which is quite deep and stops just outside the canopy drip line.

Figure 1b. A more realistic view of a tree's roots. Most roots are relatively shallow (three feet or less deep) with most roots within 12 inches of the surface. Roots extend well past the canopy drip line.

Source: www.extension.umn.edu