One of the most striking shade-loving plants is mahonia. This family of evergreen shrubs is native to the woodlands of Asia and North and Central America. In the landscape the shrubs are valued for their fascinating foliage, fragrant flowers and decorative fruit. The long leaves resemble stiff, spiked fern fronds. The panicles of yellow flowers, produced in winter or very early spring, are followed by purple, blue or red fruits which the birds love. Mahonia likes moist, well-drained, humus-rich soil, and it needs shelter from drying winds.
Mahonia aquifolium (left) is native to the Northwest. It is the state flower of Oregon where it is called the Oregon grape. Flowering in early spring, it bears edible fruit that can be used to make a tart jam or jelly. The roots contain berberine and are used as an herbal treatment for GI problems. The spiny foliage emerges bronze and ages to green. In winter it changes to purple or bronze. Hardy in zones 5 through 9, this mahonia makes a great barrier hedge in that the serrated foliage deters deer.
Mahonia repens is another Western native. This groundcover member of the clan tolerates dry shade. Another drought- tolerant mahonia hails from Mexico. Mahonia gracillis grows three to four feet tall and is cold hardy in zones 7-9.
Mahonia fortunei is a Chinese native named in honor of Robert Fortune of plant-hunting fame. This one grows six feet tall and three feet wide. It is only cold hardy to zones 8-9 so we would need a greenhouse to grow it here. It is used along the northern Gulf Coast.
Mahonia eurybracteata is another Asian import. Growing a yard tall and wide, this is a useful small shrub for full to part shade. It is spineless and spreads by suckers. To encourage new growth at the base, prune the tallest stems in early spring. I found the cultivar “Soft Caress” (right)
in a big-box garden center near my house. We added a few to fill in an area in our understory. So far we are very happy with them and they seem happy in their new home.
Mahonia japonica Bealei, a.k.a “leather leaf,” a.k.a. Beale’s barberry, has been declared an invasive plant in Alabama, Georgia, South Carolina and Tennessee. Despite its botanical moniker, Beale’s barberry has no connection to Japan. This Chinese native grows five to 10 feet tall and just as wide. Spreading by suckers, it crowds out understory natives.
By definition an invasive plant is nonnative to the ecosystem. Its introduction causes or is likely to cause economic or environmental harm or harm to human health. It crowds out competitors because its natural enemies, whether diseases or insects, are absent. Indigenous plants that spread rapidly are referred to as “aggressive” or “thuggish.” The invasive plant definition was created by the USDA/US Forest Service.
It is illegal to harbor or trade in plants where they have been declared invasive.
Master gardener Ann Bartlett would never harbor invasive plants in the ornamental gardens surrounding her home, and does not put up with aggressive or thuggish behavior from the native ones, either.