Invasion of the killer ornamentals

A tree talk with master arborist Michael Murphy

Story by Carolyn Males

A dazzling meteor shower lit up the sky and blinded everyone who’d looked up. That was bad enough, but then suddenly the earth was swarming with triffids, big hulking hungry plants that stalked and feasted on any unlucky soul they encountered. John Wyndham’s 1951 apocalyptic sci-fi thriller The Day of the Triffids (later made into a classic black-and-white movie) portrayed a nightmare scenario threatening the planet and all human existence.

Happily, no recent meteorological events have caused an invasion of carnivorous greenery. But here in South Carolina and in many parts of the country, we are dealing with a different kind of plant invasion, some of which is of our own making.

Recently, on a blistering hot day, master arborist Michael Murphy and I met on the Beaufort waterfront. Over iced coffees we talked about an upcoming state ban on invasive ornamental trees and plants you and your neighbors may have growing in and around your yards.

The perfect trees until they weren’t

[LOCAL Life] Three houses ago, our landscaper planted a Bradford pear in our front yard. In the half-dozen springs we spent there, the tree put on a glorious show of white blooms followed by glossy green leaves in summer and a blaze of red in autumn. We were not alone. Many years earlier, Ladybird Johnson had symbolically planted one in downtown Washington during her campaign to beautify America. Towns and cities throughout the Southeast picked up their shovels, and soon rows of these ornamental beauties lined the streets. 

[Michael Murphy] The U.S. Department of Agriculture developed Bradfords out of a sturdy, nicely shaped ornamental tree, and these were perfect when planted, lining up like soldiers in a row. They were also disease resistant –– the blights our regular pears got had supposedly been bred out of them. Plus, one of their big benefits was they could grow anywhere, even in poor soil. So, cities and towns could dig a hole in the sidewalk and plant them. They would grow without specific PH and with minimal water requirements, and there was very little mortality. 

[LL] Yet next month, they will be officially banned from being sold in South Carolina. 

[MM] Well, it turned out Bradford pears had bad form or structure. The branches would fall apart in windstorms, and in the Northeast anytime there was a wet snow, they would lose branches. Twenty years after planting, all those “perfect” trees were misshapen, and they’d grown faster than anyone thought they would. The U.S. Department of Agriculture thought they’d top out at 25 feet, but they grew to be 50 or 60 feet. In urban areas they blocked signs, limbs fell on cars, and they were messy. What was worse, they were supposed to be seedless and fruitless, but they were producing tiny fruit that rots and gets gooey when you step on it. The birds began spreading the seed, and the trees started growing wild. 

[LL] So this tree morphed into a monster?

[MM] When the seeds were carried into open forest areas, they took over. It’s a classic pattern where invasive trees and shrubbery grow so prolifically that they push out the natural understory [layer of vegetation] beneath native trees, taking away the habitat and food source for local animals and insects. Then they begin pushing up into the canopies of the native trees, blocking sunlight and nutrients and killing them. What’s more, if their roots grow into thorny plants, they can cross-pollinate, changing form and sprouting thorns, which hurt wildlife and anyone who comes up against them. 

Privacy hedges gone amok 

[LL] I see that some flowering olives or species of Elaeagnus shrubs – autumn-olive, thorny-olive and Russian-olive — also made the state’s “do not sell” hit list.

[MM] Elaeagnus shrubberies were designed for screening – to create privacy or block an undesirable view. You could plant just one, and it would spread. But like bamboo, the roots are shallow, and new shoots that emerge push upward, becoming new plants with branches and leaves. That would be excellent if that kind of screening just stayed there, but it doesn’t. It keeps going, going, going, and as it does, it takes over your lawn and landscaping, not to mention your neighbors’. Then, as it sprouts more tendrils, it begins growing up into any tree that’s nearby. Once it gets around the trunk and up into the canopy, it goes crazier, growing at a greater rate than the tree, covering its leaves, blocking light needed for photosynthesis; it kills the tree and the understory or native habitat below.

[LL] Kind of like the kudzu of shrubbery.

[MM] Exactly. Around 20 years ago nature-based communities like Spring Island and Bray’s Island, which had previously approved Elaeagnus for screening, started not only banning but eradicating them. If you had them in your yard, they’d ask you to take them out. 

[LL] So with this new ban, what happens if you already have any of these in your yard?  Will the plant police nab you?

[MM] No. [He laughs.] If you have an invasive tree in your front yard and you’re in a town, it’s not as bad as if you live near a nature preserve or marshes. But it’s still a good idea to remove invasive trees and plants. For the Bradford pears, I’d recommend having a tree service do it and grind the stump below grade. Elaeagnus is usually dug out or ground out by a landscaper or a tree service. Some root slips with sprouting potential can sometimes be left behind so it may take a few growing seasons to eradicate it 100 percent. 

Clemson University has a bounty program where, if you take the tree down, they’ll give you a native plant — black gum, bald cypress, overcup (white) oak, sweet bay magnolia — in exchange. However, right now it’s only active in a few upstate counties where these plants have been spreading heavily into open fields and forests. In the future they’ll be extending to other parts of South Carolina.

As for those pesky triffids

And if by chance, you encounter triffids lurching up your driveway, the eradication method for them is much simpler. (Spoiler alert!) Douse them with a bucket of seawater and watch them curl up and die. Planet Earth will thank you.

Nature’s outlaws

Invasive plants are species introduced into an area that aggressively compete with and displace native habitats, animals and plants.

Characteristics

• Rapid growth and reproduction
• Lack of natural enemies to limit their spread
• Can include volunteer species like weeds

Notable invasive species in South Carolina

• Trees: Mimosa, Tree of Heaven, Chinaberry, Chinese Tallow Tree

• Other types: Various invasive vines, grasses, sedges and herbs

Clemson University provides a comprehensive booklet listing invasive plant pest species in South Carolina. Visit the Clemson Home and Garden Information Center at hgic.clemson.edu or call 888-656-9988.