Ask Mr. Smarty Plants

Unfortunately, we find ourselves talking more and more about allelopathy, as more is being learned about it. This is a process by which a tree, usually as it matures, emits substances from leaves, twigs or even roots that inhibit the growth of competing plants beneath that tree. Species of magnolia definitely are offenders in this respect. We would certainly recommend that you remove the non-native English ivy, for reasons laid out in this Plant Conservation Alliance Alien Plant Working Group site Least Wanted-Hedera helix, (English ivy). It is an invasive plant and can damage brickwork and kill trees if allowed to grow unchecked. 

Besides the emission of toxic substances, the dense shade of Magnolia grandiflora (southern magnolia) can also prevent the flourishing of understory plants. However, we will suggest a few shade plants, a couple ferns and some grasses, that could hopefully overcome both disadvantages and give you an attractive native cover beneath the tree. The Lady Bird Johnson Wildflower Center recommends only plants native not to North America and to the area in which they are being grown; plants already acclimated to the climate, rainfall and temperatures will require less maintenance, water and fertilizer.

Plants for under a magnolia tree

Athyrium filix-femina (common ladyfern) - 2 to 3 ft. tall, part shade, shade

Calyptocarpus vialis (straggler daisy) - 6" to 1 ft. tall, sun, part shade, shade

Hydrocotyle umbellata (manyflower marshpennywort) - 6" to 1 ft. tall, sun, part shade, shade

Onoclea sensibilis (sensitive fern) -  to 3 ft. tall, part shade, shade

Phlox divaricata (wild blue phlox) - 8" to 18" tall, part shade, shade

Ruellia drummondiana (Drummond's wild petunia) - 1 to 3 ft. tall, part shade, shade

Viola lanceolata (bog white violet) - part shade, shade

Viola missouriensis (Missouri violet) - 6" to 1 ft. tall, part shade, shade

Grasses for under a magnolia tree

Bromus ciliatus (fringed brome) - sun, part shade, shade

Chasmanthium latifolium (Inland sea oats) - 2 to 4 ft. tall, part shade, shade

Muhlenbergia schreberi (nimblewill) - 1 to 2-1/2 ft. tall, part shade, shade

Sorghastrum nutans (Indiangrass) - 3 to 6 ft. tall, sun, part shade, shade

Athyrium filix-femina

Calyptocarpus vialis

Hydrocotyle umbellata

Onoclea sensibilis

Phlox divaricata

Ruellia drummondiana

Viola lanceolata

Viola missouriensis

Bromus ciliatus

Chasmanthium latifolium

Muhlenbergia schreberi

Sorghastrum nutans