The beauty of gardening under trees
Story and Photos by Troy B. Marden
Gardening under trees can be difficult. I know. I have a love-hate relationship with the two enormous white oaks that allow me to even have a shade garden, but, at the same time, render the soil so dry in midsummer it’s a wonder any plant even survives, let alone thrives. Fear not. While there are some inherent challenges, gardening under trees does not have to be an effort in futility and, in fact, can be some of the most rewarding gardening you will ever do.
Masses of cool green ferns paired with the broad, architectural foliage of impressive clumps of Hosta are the classic shade garden combination, but the opportunities under a well-managed tree canopy range far beyond the typical hostas and ferns. Lenten rose (Helleborus spp.), Solomon’s seal (Polygonatum spp.), mayapples (Podophyllum peltatum), gingers, and even some peonies (Paeonia spp.) will thrive in these woodland settings, making for some of the garden’s most beautiful and charming vignettes.
One of the primary challenges when gardening under trees is water, or lack thereof. Trees are thirsty and, being the largest members of the landscape with the largest root systems, they can – and will – quickly rob the soil of valuable moisture, especially in the heat of summer. It is important, therefor, to choose plants that will tolerate a moderate to high degree of drought. Many popular shade garden plants, being native to forested areas to begin with, are already prepared for the drought challenge. Even so, additional irrigation during the hottest and driest months of the year is highly beneficial when it comes to keeping plants looking their best.
The second challenge of gardening under trees is the physical presence of tree roots. If you can’t get a shovel in the ground because a network of roots has made the soil impenetrable, it is going to be very difficult to grow any plants – even the toughest ground covers – successfully. Trees like river birch (Betula nigra) and red maple (Acer rubrum) create dense masses of tiny feeder roots stretching many feet in every direction from the trees’ primary roots and make them the most difficult to garden under. Not only are those surface roots robbing other plants of precious water and nutrients, they can, and will, physically strangle smaller plants. Oaks (Quercus spp.), tulip poplar (Liriodendron tulipifera), beech (Fagus spp.), and other deep-rooted species are much easier, both on the gardener’s back and on the plants you’re trying to grow, since these species are drawing more of their water from deeper in the soil, as well as giving less physical competition to the roots of your perennials, shrubs, and ground covers.
If you’re fortunate enough to have old, established woodland areas where the soil is rich and deep from many years of naturally decomposing leaf litter, you’re already well ahead of the game. Not all of us are so lucky. This natural layer of compost contains billions of beneficial microbes, helps retain soil moisture and nutrients, and allows the roots of perennials, shrubs, and ground covers to penetrate deep into the soil. These are all advantages when it comes to plants thriving under trees. If you, like me, don’t have this natural layer of woodsy humus available to you, deep-rooted trees make it possible to give our garden soil a little help by adding garden compost, worm castings, soil conditioner, and other organic amendments to help improve the soil and create the rich layer of topsoil where shade-loving plants will thrive. By adding a 1-inch layer of good compost and making a light application of organic fertilizer to my shade garden each year, I have been successful, in spite of the summer drought that my beautiful oaks inevitably cause.
The third challenge(s) when gardening under trees are the pests who have an insatiable appetite for some of the best choices for these conditions. Deer are the most obvious of these and, as too many gardeners already know, will strip a shade garden clean of hosta foliage overnight. Azaleas (Rhododendron spp.) are on the menu, too. They will also nibble some ferns, Solomon’s seal, mayapples, and many others, though it is often more casual browsing on these species rather than complete devastation. Lenten rose, lily-of-the-valley (Convallaria majalis), and gingers are some of the most deer-resistant species.
Voles are also a serious problem in many shade gardens. These are voles, with a “v” – not moles, with an “m.” There is a difference. Voles are small creatures that resemble field mice. The difference is, that they have giant (for the size of the animal) front teeth that can do irreparable damage to plant roots in no time. Opportunistic, they use the runs of moles and chipmunks as superhighways that lead directly to the roots of a plant where they feed voraciously. If you have experienced the sudden, overnight death of plants that collapse without warning, this is most often vole damage. Even mature shrubs are not safe. If, after the sudden death of a favorite azalea (or other shrub), you can pull it straight out of the ground with almost no roots attached, voles are the culprits. On woody plants, you can often see the marks of their tiny, beaver-like teeth around the base of the plant. It is most frustrating!
Challenges notwithstanding, shade gardening is some of the most rewarding gardening you can do. My solution has been to experiment with a broad range of plants, assess which of those are most successful, and then delve deep into the different cultivars available of each type to keep the plant palette diverse and interesting. The rich textural combinations, the subtle play of shades of green, the pop of “sunlight” added by a gold-leafed variant of a favorite plant, and the ability to weave rich tapestries of foliage and flower are always a delight. And the successful creation of a thriving shade garden does secure the gardener a certain level of bragging rights.