Gardening: New invasives to watch out for

Amur honeysuckle, shown here with its distinctive berries, is one of the latest plants to be placed on Maryland’s “Tier 1” list of invasives. Such plants are targeted for the highest level of efforts to find and prevent them from spreading within the state.

I was working at a plant sale when a woman with that obsessive gleam of a plant lover in her eye came over. Our handful of volunteers from a horticultural association snapped to attention, happy to see a potential customer braving the pouring rain.
“That plant’s a Tier 3 invasive,” she said, pointing to a small green thing whose name I didn’t know. We saleswomen looked at each other, mystified. Who knew the plant was an invasive? And who was she? An inspector from the plant police?
Never one to be bashful about my ignorance, I asked: “What’s a Tier 3 invasive?”
Turned out the shopper worked for a branch of government dealing with plants, but didn’t want to divulge details and didn’t want to be interviewed. She had a garden stuffed to the gills with native plants, she said, so she didn’t have room for any more … but maybe she’d have a quick look. I know the ways of a plant fanatic, being one myself.
Whether she bought anything, I don’t recall. What I did remember was the mysterious term “Tier 3 invasive.”
The ways of government can be complicated to an extreme. Hours of research netted me information about Tier 3, as well as Tiers 1, 2, 4 and 5. More on that later. What really caught my attention, however, was news that Maryland had designated more plants as invasive.
Yellow flag (the iris one often sees growing in drainage ditches), shining geranium and fig buttercup (also called lesser celandine) officially joined some invasives we’ve probably all heard of, like kudzu, on the Tier 1 list in mid-April. As of Feb. 18, 2018, wintercreeper and amur honeysuckle will go on the list.
Other plants, designated Tier 2 this year and last, are: Scotch broom, burning bush, border privet, nandina, Japanese wisteria, Chinese wisteria and a wisteria hybrid called floribunda x sinensis.
What’s confusing for the average gardener is that not all wisterias – or honeysuckles, for that matter – are equal. Atlantic, or American, wisteria is a “good” plant. It’s a native,
The U.S. Fish & Wildlife Service‘s book “Native Plants for Wildlife Habitat and Conservation Landscaping — Chesapeake Bay Watershed” says native wisteria (wisteria frutescens) produces lilac-colored flowers from April through August. It favors “forest, forested swamp edges, stream banks and thickets” and will take full sun or part shade. The book mentions nothing of the lovely fragrance many of us associate with wisteria. Who knows which wisteria has enchanted my nose over the decades?
Another tricky plant is honeysuckle. The one most of us imagine, when hearing the charming name, is a vine that blankets buildings, bushes and trees (which it can strangle) and produces fragrant yellow flowers that attract pollinators in summer and fall. It’s Japanese honeysuckle, a notorious invasive.
However, other types of honeysuckle exist. Some are vines, others bushes. A number of them appear in the rogues’ gallery of invasives. Just one is a native: Trumpet or coral honeysuckle (lonicera sempervirens ).
The native, like its aggressive relative, has the great advantage of being semi-evergreen and attracting a host of wild creatures – butterflies, hummingbirds, songbirds and beneficial insects. But it has the drawback – in my book – of smelling of nothing at all. Maybe the wildlife can smell a fragrance we humans cannot.
Lonicera sempervirens is lovely to look at and won’t take over everything in its path in no time flat. The native landscaping book describes its blossom as “coral to red with yellow.” It flowers from April through October and produces red berries from August through March. Growing six to 12 feet and blooming in sun or part shade, the plant favors “thickets, fence rows, open woods, dry stony woods, forest edges and cliffs.
So, there are two lovely plants you might consider acquiring this month, when many garden centers and native plant suppliers have their fall sales. Tomorrow and Saturday, Environmental Concern in St. Michaels has a fall plant sale from 9 a.m. to 2 p.m. Adkins Arboretum has its fall open house and native plant sale tomorrow through Sunday.
Back to the thorny subject of invasives. If you’re lucky enough not to have any in your garden, you may wonder, why worry? Invasives, in my opinion, may be the single worst problem threatening our gardens and the natural landscape. If they’re not in your garden today, they may be tomorrow.
And plants are not the only invaders. Japanese beetles and brown marmorated stinkbugs are invaders from Asia, for example. Plant diseases like sudden oak death and Dutch elm disease are invaders, too.
What can a gardener do? For one thing, keep abreast of the newest invasives by checking the websites www.mdinvasivesp.org and www.mda.state.md.us/plants-pests. Watch for invasives in your garden and community. Eradicate them and check the Maryland Department of Agriculture website for restrictions on how to dispose of them. Wood from a tree infected with sudden oak death, for example, should not be dumped in a landfill or transported in an open truck, for fear of spreading the disease.
Alert other people to the threat of invasive species and, if you find a fast-spreading, unusual plant, bug or disease, report it to the authorities.
Be aware that some invasive plants are “of commercial importance to the nursery industry” and “routinely sold and planted in Maryland,” according to the Maryland Invasive Species Council. Landscape architects, designers and installers, as well as home gardeners, should consider alternatives to these dangerous plants, the Council warns.
To help recognize invasives, guides can be found online and in stores. Best are the most recent because experts are constantly adding to the lists. Consult www.invasive.org to find all 1,669 plants considered invasive by the Center for Invasive Species and Ecosystem Health.
Maryland updated its law on invasives last spring. Tier 3 plants, such as giant hogweed, are those believed already too widespread for eradication. The goal is to slow their spread. Tier 2 plants, such as mile-a-minute, are seen as still at the stage where they could be eradicated.
Stores and nurseries selling Tier 2 plants must put signs beside them identifying them as invasive. There’s a fine of up to $500 for each violation. Gardening professionals planting such species must give their customers a list of the Tier 2 invasives.
Would that I had enough space to tell you more. But I don’t. So, watch out for invasives and, in the meantime, happy gardening!
Editor’s note: Laetitia Sands is a master gardener in Dorchester County.

 

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