A large maple tree provides cooling shade and is a handsome specimen to anchor an entire landscape. Unfortunately, even the smallest maples present landscaping challenges because of their shallow, long-reaching roots and thirsty habit. “Easy does it” is the rule when landscaping under and around these big trees with delicate toes.
Maples (Acer spp.) come in a variety of shapes, from the towering bigleaf maple (A. macrophyllum) to delicate 2- to 3-foot tall Japanese maples (A. palmatum). All have shallow, fine roots that reach out more than twice the width of the tree’s mature crown. Because they are so shallow, with 90 percent of tree roots in the top 3 feet of soil and the majority of roots in the top 1 foot of soil, the maple’s dense crown draws enough water from the soil around the roots to create a shady, arid space directly below the tree’s crown.
Hardscaping Near Maples
If you destroy the ability of roots to gather water and nutrients up into the tree’s limbs, the limbs will suffer shock and begin dying back. Building walkways or garden shed foundations requires excavation and the closer you dig to a maple tree’s trunk, the more roots you’ll sever. If excavation is essential, it is best kept beyond the tree's canopy. Increasing the grade by building a raised garden around a tree or terracing a hill can also adversely affect a maple, as the added soil depth and compaction caused by its weight, plus the equipment used to transport it, block air and water and in the worst case, lead to root rot.
Around the Trunk
Maples grow a dense, low crown. Removing lower branches when they are 3 to 4 inches in diameter allows more air to circulate through the crown and sunlight to shine underneath it. As long as a proportion of two-thirds crown to one-third trunk is maintained, up to 10 feet of lower branches can go. Even with this trimming, turfgrass and sun-loving annuals won’t get enough sun and would compete for water, necessitating irrigation. A donut of mulch, spread to a diameter of at least 6 feet out, prevents evaporation of ground moisture and protects the trunk from string trimmers and mower blades.
Planting Under Maples
Shade-tolerant perennials can add color and will expand each year. Shade-loving Western chain fern (Woodwardia fimbriata), California wood fern (Dryopteris arguta), common wood fern (D. expansa) or Pacific trillium (T. ovatum ssp. ovatum) will grow under the shade of the crown, and planting them at least 4 feet from the tree's trunk will avoid damaging roots. Seedlings require smaller planting holes than full-grown container plants, causing less root damage. Spring bulbs such as jonquils and irises or perennials such as daylilies and hostas thrive in the dappled shade near and beyond the tree’s drip line.
Your Planting Articles
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- University of Minnesota Sustainable Urban Landscape Information Series: Planting Under Existing Trees
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