The ‘Saint Mary’ Southern Magnolia, a cultivar of Magnolia grandiflora, offers a distinct presence in diverse landscapes. Its refined form and evergreen foliage make it a popular choice for enhancing garden aesthetics. This tree provides year-round visual interest and can serve as a focal point or an elegant screening element.
Understanding the Saint Mary Southern Magnolia
The ‘Saint Mary’ Southern Magnolia, Magnolia grandiflora ‘Saint Mary’, is a compact, pyramidal evergreen tree with dense branching. This cultivar typically reaches a mature height of 20 to 25 feet and spreads equally wide. Its distinctive foliage features large, green leaves with a bronze or rusty underside, providing year-round visual interest.
This magnolia produces large, fragrant, cup-shaped white flowers from mid-spring through summer, releasing a pleasant scent. Following flowering, fuzzy brown, cone-like fruits containing bright red seeds develop. The ‘Saint Mary’ cultivar thrives in USDA Hardiness Zones 7 through 9.
Planting and Site Selection
Selecting the optimal site for a ‘Saint Mary’ Southern Magnolia is important for its long-term health. This tree flourishes in full sun to partial shade, ideally with at least six hours of direct sunlight daily. In hotter climates, providing afternoon shade can prevent stress from intense sun exposure. It prefers well-drained, acidic to neutral soil rich in organic matter, with an optimal pH range of 4.5 to 6.5.
When planting, dig a hole two to three times wider than the root ball and only as deep as the root ball. This wider hole allows roots ample space to spread. Loosen the root ball if compacted, then place the tree so the topmost roots are level with or slightly above the surrounding soil line. Backfill the hole with soil, pressing gently to remove air pockets, and water thoroughly to settle the soil around the roots.
Ongoing Care and Maintenance
A consistent care routine ensures the vigor of a ‘Saint Mary’ Southern Magnolia. For newly planted trees, regular, deep watering during the first few growing seasons is essential to encourage an extensive root system. Once established, the tree becomes moderately drought-tolerant, but it still benefits from deep, infrequent watering, especially during dry periods.
Fertilization supports robust growth and flowering, best applied in early spring before new growth emerges, typically March or April. A balanced slow-release fertilizer, such as a 10-10-10 or 14-14-14 formula, works well for magnolias. Due to their wide-spreading root systems, fertilizer should be spread broadly, 6 to 10 inches out from the trunk and extending to the tree’s drip line. Applying a 2 to 4-inch layer of mulch, such as pine bark, around the base helps retain soil moisture, suppress weeds, and regulate soil temperature.
Pruning for ‘Saint Mary’ Southern Magnolias is generally minimal, as they naturally maintain their form. Any necessary pruning to maintain shape, manage size, or remove damaged branches should be performed after flowering, typically in late spring or early summer. This timing avoids removing current season’s flower buds, ensuring a continuous display of blooms.
Common Issues and Solutions
Even with proper care, ‘Saint Mary’ Southern Magnolias can encounter issues, with yellowing leaves being a common concern. Yellowing foliage, particularly if veins remain green (iron chlorosis), indicates alkaline soil, impeding the tree’s ability to absorb iron and other nutrients. Soil testing can confirm pH levels, and amendments like elemental sulfur or organic matter can help acidify the soil. Insufficient or excessive watering can also lead to yellowing leaves, so monitoring soil moisture is important for consistent hydration.
Pests like scale insects, aphids, and spider mites can affect magnolias. Magnolia scale is a common culprit, and infestations are often managed with horticultural oil applications. Fungal spots and canker diseases may appear, but these rarely require chemical controls; pruning affected branches can help limit their spread. Maintaining overall tree health through proper planting, watering, and fertilization helps the ‘Saint Mary’ Southern Magnolia resist common problems.