Knowledgebase

Is it harmful to plant non-native plants #778210

Asked November 22, 2021, 11:02 AM EST

We are preparing to plant a few small shrubs in the front of our house. We are looking for something less tame than a boxwood. The area is partially shaded, especially in the winter. Our landscaper suggested planting Nandina Domestica. I see this is not a native species. What are the pros and cons of planting non-native plants? Thanks!

Frederick County Maryland

Expert Response

Non-native plants, assuming they are non-invasive, can be part of a landscape and cause no serious detriment. However, it's recommended that native species comprise at least 70% of those on the property - everything from lawn to flowers to shade trees - in order to support wildlife (mainly native insects, since so much of the food web depends on them). Fortunately, we have a wide array of native plants to choose from, though not many shrubs are evergreen.

Pros and cons of non-native plants depends somewhat on your perspective and priorities. (Once again, this assumes the non-native plants are non-invasive.) One pro to non-natives, which tend to avoid insect feeding damage, is that they can be relatively pest-free - a benefit for aesthetics and which should reduce people's inclination to use pesticides. However, this lack of insect damage can also be seen as a con when it comes to supporting biodiversity, since insects that feed on plants are key food sources for a wide array of animals, including songbirds. A more neutral benefit of non-natives could simply be the expansion of the plant choices suitable for a given site (that is, it gives you many more choices of what to plant). Plus, just by taking-up space and stabilizing the soil, they may help to prevent the appearance of invasive species if a native alternative isn't as well-suited to that planting site and would struggle to survive.

Some research results have suggested that a diverse landscape (in terms of plant variety as well as a range of mature plant heights) can support an equally-wide array of wildlife as well as a native-only landscape could. The take-home message in that case was that planting a varied landscape would be better than a simpler, sparser landscape, regardless of plants used. Ecologists would counter-argue, though, that native species are always preferred because they can support specialist insects that cannot utilize non-native plants as a food source. Generalist insects tend to get by well enough on their own without our help, since they by definition can use a wider range of plant species; it's the specialists we need to support with native plant use.

Yes, Nandina domestica is not only non-native, but it can be invasive. Its sale is restricted by the Maryland Department of Agriculture such that nurseries and landscapers must inform the purchaser that they can be invasive and that alternatives should be considered. See the Tier 2 Invasive Plants section of this page, and you can view both tier lists on this page.

You can read more about avoiding invasive plants (and the problems they cause) on this page and its included links (both in the text and at the bottom of the page): https://extension.umd.edu/resource/invasive-plants-avoid-buying-your-yard-and-garden-maryland

Shade in winter is not as important a factor in plant light preferences as shade versus sun during the growing season (mainly summer). There are a few options among locally-native, regionally-native (outside MD but still in the eastern U.S.), and non-native shrubs you can consider if you don't wish to use Boxwood. Below are some ideas, but the list is far from exhaustive. Some may be harder to find at area nurseries but might be available online if you wish to try them. Given climate change trends, those currently at the colder edge of their hardiness tolerances here in MD may be less risky as time goes on.

  • Leucothoe (Leucothoe axillaris, Leucothoe fontanesiana, Agarista populifolia) - regionally native; evergreen;"lax" growth (that is, not as rigid and dense as Boxwood); deer tend to avoid
  • Anise-shrub (Illicium parviflorum, Illicium floridanum, and a few hybrids) - regionally native; evergreen; vaguely Rhododendron-like in appearance but less fickle about soil wetness; prefers shade over sun; deer tend to avoid
  • Yaupon Holly (Ilex vomitoria) - evergreen but non-prickly, happens to look very similar to Boxwood; won't produce berries unless you plant a male or two amid female cultivars; several cultivars of varying shapes at maturity, though tolerant of pruning
  • Japanese Plum Yew (Cephalotaxus harringtonia) - evergreen; deer tend to avoid; several cultivars, some taller than wide, some low and broad
  • False Holly (Osmanthus heterophyllus) - evergreen; spiny, holly-like foliage, though becomes less prickly with age; very fragrant small autumn blooms; deer tend to avoid; a couple of dwarf varieties are available, though plants tolerate some pruning
  • Sweetbox (Sarcococca confusa) - evergreen; groundcover species more common than this one, which is rounded and not spreading; deer tend to avoid; very fragrant small late-winter blooms
  • Spicebush (Lindera benzoin) - locally native; deciduous; not short but suitable if you don't need to worry about blocking a window; host plant for the Spicebush Swallowtail butterfly
  • Mountain-laurel (Kalmia latifolia) - locally native; evergreen; can be fickle about soil type, especially drainage since it won't tolerate sogginess; several dwarf and compact varieties exist since they don't prune well

 

Miri

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