The question comes up almost every week: can I cover the exposed roots of my tree? The mower keeps stalling on it, the postman trips on it, the kids can’t play on it, the grass is dead and I’ve tried everything but it won’t grow back…”
The short answer is “Yes” – don’t kill your tree in the process.
Despite popular myths, trees do not naturally have deep or shallow roots; Depending on the type of soil and the availability of water and air, trees that we consider to have shallow roots can have roots several feet deep, and supposedly deep-rooted trees often have shallow roots. directly on the surface. You’ve seen them knocked down, with roots only a foot or two deep.
This is because although roots generally grow downwards, they need oxygen to process things; if the soil is heavy clay or poorly drained and remains wet for weeks, the roots cannot get the oxygen they need and either do not grow deep or rot.
Ultimately, if a tree has roots above ground, it’s usually because they can’t grow any deeper, so covering them more than a few inches with soil can choke them out. Not always, but believe me, I see it happening all the time.
So what to do? There are three good options (four, really, if you don’t notice them at all). You can celebrate them by removing the leaves and leaving them in plain sight; you can cover them with a mulch of leaves, bark, pine straw, gravel, chipped slate, spaced flagstones, or another porous material that still lets air and water reach the roots; or you can plant ground covers or small, shade-loving shrubs. All three work and are commonly done in botanic gardens.
I like the first, in which a distinct line is cut in the ground outside the exposed roots so that the area has a distinct shape, allowing the gnarled roots to rise from the bare earth or moss like a important, old and even showy part of the tree . The line can be a shallow trench, metal edging, bricks, or monkey grass, it doesn’t matter as long as it seems useful. When the leaves fall, simply blow them under the tree to replenish the soil.
Planting under mature trees can be a challenge, aside from the difficulty of digging up organic matter in weak spots between tree-sized roots. There aren’t many opportunities to give whole new plants a good start that need their own breathing room, and you only get one chance, so do your best (hint: c easier one day after a good pouring rain).
When it comes to plants, there aren’t many that can tolerate heavy shade and competition for root space and moisture; some are unfashionable or can be invasive without borders. The most commonly planted and attractive low-growing ground covers I see thriving under mature trees in older neighborhoods include English ivy, Vinca major, Liriope, mondo grass, Asiatic jasmine, Moss and Ajuga. There are others, but these reign supreme.
The problem is that the factory approach takes time; the old horticultural adage is “the first year they sleep, the second year they crawl, the third year they jump”. Meanwhile, add a few clumps of taller shade plants like ferns, aspidistra, hostas, daffodils and azaleas or other small shrubs, as well as a bench, chairs, urn, bath birds, driftwood or any other “hard” item for instant appeal.
Whatever you do, remember that these bark-covered behemoths are the shoulders of outstretched arms and are important to the tree. Important enough to protect and celebrate, rather than hide.
Felder Rushing is a Mississippi “Gestalt Gardener” author, columnist and host on MPB Think Radio. Email gardening questions to [email protected].