A mature magnolia tree anchors any landscape, providing deep shade and fragrant flowers. However, the space beneath its broad canopy is challenging for gardeners seeking to add underplantings for color and texture. Finding suitable plants and installing them without harming the tree requires a specialized, low-impact approach. This guide offers practical solutions for successful underplanting beneath a magnolia.
Understanding the Unique Growing Conditions Under a Magnolia
The primary constraint for planting beneath a magnolia is its distinctive root architecture, which is shallow, wide-spreading, and highly sensitive to disturbance. Magnolia roots are surface feeders, concentrating in the top 12 to 18 inches of soil to absorb water and nutrients efficiently. Disturbing this expansive network by digging can cause irreversible damage, creating wounds that invite disease or rot into the tree’s system.
The dense, leathery foliage, particularly on evergreen varieties like Magnolia grandiflora, creates a zone of deep, consistent shade beneath the crown. This limited light means any companion plant must be highly shade-tolerant. Furthermore, the tree’s leaf litter—the large, tough leaves that drop continuously—decomposes slowly.
The slow decomposition rate, combined with the fact that magnolias thrive in slightly acidic soil (ideally a pH between 5.5 and 6.5), dictates plant selection. The constant layer of litter reinforces this acidic environment, favoring only species that tolerate a low pH. Additionally, some magnolias exhibit allelopathic properties, releasing chemical compounds that can naturally inhibit the growth of competing plants.
Low-Impact Planting Techniques to Protect Magnolia Roots
The most important rule when planting beneath a magnolia is to avoid deep digging, as standard hole excavation can sever the tree’s fine feeder roots. Gardeners must adopt a low-impact methodology that respects the integrity of the shallow root system. Never use a shovel or spade; only dig holes manageable with a small hand trowel or garden fork.
A technique known as top-dressing or sheet mulching is the preferred method for introducing new soil without disturbing established roots. This involves lightly layering a high-quality, humus-rich soil mix, such as compost blended with topsoil, directly over the existing root zone. The new layer should be kept very shallow, ideally no more than one to two inches deep, to prevent suffocation of the tree’s roots.
When selecting plants, choose small transplants, plugs, or divisions rather than large, root-bound container specimens. These smaller plants require significantly less soil disturbance and can be gently tucked into the shallow layer of new soil and compost. If a large root is encountered, immediately shift the planting location instead of attempting to cut or maneuver around the obstacle.
After installation, consistent watering is especially important during the plant establishment phase. The magnolia’s dense canopy intercepts rainfall, resulting in a significantly drier environment beneath the tree than in the surrounding landscape. Applying a thin layer of organic mulch over the newly planted area will help retain moisture and suppress weed growth.
Specific Plant Recommendations for Deep Shade and Acidic Soil
Selecting plants that thrive in deep shade, drier soil, and acidic conditions ensures the health of the tree and the success of the underplanting. Shade-tolerant groundcovers are often the best choice for creating a cohesive look while competing minimally with the magnolia roots. Vinca minor (Periwinkle) and Ajuga reptans (Bugleweed) are excellent low-growing options that form dense mats, with Liriope (Lilyturf) offering a contrasting grass-like texture.
For adding height and varied foliage, certain perennials perform exceptionally well in this challenging environment. Hosta, particularly smaller varieties, is highly adaptable to deep shade and dry conditions, providing strong visual interest. Various ferns, such as the evergreen Christmas Fern or the Japanese Holly Fern, introduce a delicate, feathery texture and tolerate dry shade.
Adding color earlier in the season is possible with spring-flowering bulbs, which often complete their bloom cycle before the magnolia’s canopy fully develops. Small bulbs like Snowdrops and Crocus can be gently inserted into the shallow soil layer between the roots. Daffodils also tolerate the conditions well, blooming in the early spring light before the deep summer shade sets in.
Low-growing shrubs can be strategically placed along the outer edges of the canopy where light levels are slightly higher. Acid-loving plants such as Dwarf Azaleas and Rhododendrons are naturally suited to the lower soil pH preferred by the magnolia. Japanese Holly is another evergreen shrub that tolerates acidic conditions and shade, providing year-round structure without requiring deep digging for installation.