New Invasive in Durham's Duke Forest Neighborhood

Here is an exhilarating but scary detective story about a pretty but ecologically dangerous plant. After finding Lesser Celandine (Ranunculus ficaria, also known as fig buttercup) in a yard in the Ellerbe Creek watershed, which feeds the Neuse River watershed, I described the plant to my friend Perry, who knows Durham and the NC piedmont very well. He said he had seen the species in a backyard in the Duke Forest neighborhood, which drains into the Cape Fear River. He had at first wondered if it was a rare wildflower, until he later saw it running rampant over a stream restoration site in Greensboro, NC.

When he showed me the plants he had seen in the Duke Forest neighborhood yard, I began tracking them upstream, using the instinct I had developed in tracking the similarly invasive Garlic Mustard in the Ellerbe watershed.

Close up, the plant looks like this. These flower stalks seemed longer than those in the Watts-Hillandale neighborhood yard.

Upstream were a series of larger patches. I felt like a sleuth in a detective movie, or maybe it was the primal rush of the hunt--something our minds evolved for but seldom have the chance to do.

When the brush became too dense, I returned to the road to explore further upstream. At Pinecrest and McDowell, I found one of the plants growing on the curb, an odd location since the rest of the infestations had been down along the stream bank. Note the storm drain that feeds straight into the floodplain of the creek this road crosses.

I looked down into the woods near this curb, and found the floodplain blanketed with the invasive, showing just how dominant and exclusionary of any other low-growing species it can become. Lesser Celandine has the potential to outcompete the many native species of spring wildflowers, and thereby impact the wildlife whose taste buds have not evolved to eat exotic plants.

Though the neighborhood has the protection of speed limits and Neighborhood Watch, there has been no one looking out for exotic plants that are able to invade gardens and speed downstream to infest natural areas.

Upstream of the intersection, the trail went cold, meaning that the infestation must have been entering the creek there from one of the side streets.

I followed a false lead to the left, then headed up McDowell Street. Near the top of the rise, I saw a hillside of yellow and knew I'd found the source of the infestation.

It's hard to predict how the homeowners are going to respond when you knock on their door and let them know they have an ecological menace growing in their yard. But this time, the news was very well received. At first they were puzzled, then tremendously thankful for having someone explain what was going on with this super aggressive plant.

They had liked the flower at first, but had grown increasingly concerned as it invaded the Vinca minor they had hoped would populate the hillside. The blue flowers of the Vinca can be seen amidst the sea of yellow in the photo. Though Vinca minor can also be thought of as an invasive, it doesn't spread downstream to new areas like the Lesser Celandine does.

We speculated that the seeds or perhaps the underground bulbules of the invasive had been washed down the driveway, then down along the curb until they reached the creek at the bottom of the hill, where they quickly began to spread downstream.

I had to return to New Jersey the next day, but Perry said he would track the flower downstream to determine the extent of spread. This sort of invasives work benefits from a Swat Team mentality, where swift action determines whether the invasion can be stopped while still limited in scope. Once the plant stops blooming, it will be much harder to track. In another month or so, the plant will turn brown and "melt" back into the ground, where it will remain dormant and be invisible until it emerges again next spring.

Fortunately, the homeowner promised to spray the plants in his yard. He also said he'd remove the plant from his sister's yard in the headwaters of the Eno River, where he planted some before realizing how invasive it can be. In speculating how it might have gotten into his yard, he remembered having gotten compost from the Durham landfill somewhere between five and ten years ago.

This means a visit to the Durham landfill compost site, long since closed, is in order, to see if there is an infestation there. Still to be determined is how to deal with all the plants that have already spread down the creek.

A Wetland Garden Survives at Durham's Williams Water Treatment Plant

If you drive west on Hillsborough Road, past the Durham city reservoir, glance towards the reservoir and you will see a special but largely unnoticed feature with a long history. When it rains, stormwater from the road flows down this slope and settles in a circular area surrounded by lawn. Swampy, hard to mow, it proved a perfect place to put a wetland garden. The white sign, installed by the city and visible in this photo, says "This Natural Area Maintained By Volunteers From the Watts-Hillandale Neighborhood Association." Well, sort of.

On March 30, two volunteers showed up to give this wetland garden a much needed spring cleaning. Cynthie Kulstad lives in the Northgate Park neighborhood, and is preserve manager for the Ellerbe Creek Watershed Association. I'm a former member of the Watts-Hillandale neighborhood now living in New Jersey. It's fair to ask what's so special about this place, other than its location next to a beautiful, historic water plant. Why would two people descend on a drab-looking cluster of dried stalks to work on a hot spring day for two hours?

Here's one of them, the remains of the flower stalk of wild senna, a beautiful native wildflower that thrives in wet soils. Some years back, we planted this and other wetland wildflowers here, taking advantage of the consistently wet ground. Elsewhere on the reservoir grounds, a demonstration xeroscape garden was planted in the early 90's with grant funds. The idea was to show how to grow a garden that didn't need much water (and thus help prevent Durham from running out of drinking water during droughts). They also applied a fertilizer called Bull Durt, which was made by composting together mixed paper and sewage sludge--two materials that otherwise would have gone to the landfill. I'm sure the garden looked great at first. It won an award, then went in to steady decline due to poor maintenance by untrained city staff. After moving to the Watts-Hillandale neighborhood in 1995, I organized neighborhood volunteers to try to resurrect the gardens, which were in three "pods" over near Hillandale Road. We made some progress, but the dry conditions there made the garden susceptible to drought. One of them, I later realized, was located atop a buried old asphalt basketball court. 

After a few years of experience growing native plants in Durham, and after lugging many a bucket of water during extended droughts, I figured out that the easiest way to sustain a wildflower garden is to locate it in a wet, sunny area.

Thus, we finally got smart and moved the remaining plants to the lowest ground at the reservoir, where this brick-lined spring once quenched the thirst of golfers playing what used to be the third hole of Hillandale Golf Course. The water is muddy because the site now receives runoff from Hillsborough Road during rains. But I love this hidden historic feature, and the mystery of how a spring could have been so close to a ridge dividing the Neuse and Cape Fear river basins. (Hillsborough Road runs along that ridge.)

Along with the periodic influx of water from the road, this garden's longevity owes to it being cared for by knowledgeable gardeners rather than untrained staff with little interest in plants. City maintenance crews are good at mowing grass, however, and we are thankful to them for respecting the boundaries of this garden.

Since I now live in NJ, it's hard to do much maintenance myself. You can tell that no one in the neighborhood has yet fallen in love with this garden, because it was getting overrun by brambles, and one of the weed trees was ten feet high. It's a callery pear, a noxious, thorny invasive tree whose shade was a threat to the sun-loving wildflowers. We cut and treated the tree sprouts, cut, trampled and treated as much of the brambles as we could, flattened the old flower stems so they could rot back into the ground, and admired all the wild senna, cutleaf coneflower and iris emerging. Without this periodic selective weeding, the wildflowers would fade away under a wave of brambles and trees. In coming months, this wetland garden will bloom and provide food, water and cover for wildlife in what is otherwise a large expanse of turf.

The garden could use more attention. Even someone unskilled with caring for native plants could come by and pick up the litter carried down the hill by the stormwater. Its a fine destination for any neighbor wishing to combine an evening walk with a little care for the neighborhood. But in the meantime, Cynthie and I did the basic maintenance. A garden kept going by four hours of work per year? That's the magic of a wetland garden.

INVASIVE ALERT: Lesser Celandine Found in Watershed

While visiting Durham this past week, I was driving through the Watts Hospital-Hillandale neighborhood when I saw a blaze of yellow and thought "Oh, oh."

First time I saw this plant, in Princeton, NJ, I thought it was pretty. Then I saw how it was spreading rapidly through nature preserves, displacing native wildflowers as it forms dense, impenetrable colonies.

I happened to know the woman whose yard it was growing in, and stopped to knock on her door. She gave me a tour. She was quite proud of the yellow flower (Ranunculus ficaria--sometimes called Fig Buttercup or Lesser Celandine), and had received many compliments from neighbors on its beauty.

She had, though, noticed that it was starting to take over.

In the five or so years since it spontaneously showed up in her yard, it had spread along her walkway, made blotchy mounds in her front lawn,

and even started to push back on her english ivy.

It's hard to ask any homeowner who has been pleased with a flower to begin viewing it as an ecological threat to the watershed. Just beyond this quickly spreading patch in her backyard is a small tributary of Ellerbe Creek, which in turn is a tributary of the Neuse River.

If, or more likely, when, the lesser celandine in her yard gets in to the creek, it will spread rapidly downstream.

But it's pretty, one might say, and survival of the fittest is nature's law. But this exotic plant left its natural predators back in Europe, and so has an unnatural competitive advantage over native species. Since nothing appears to eat it, any floodplain or yard that Lesser Celandine comes to dominate will become devoid of food to sustain wildlife.

The best thing that can happen in this instance is to have the invasive sprayed, and replaced with plants that won't take over. If the homeowner can be convinced the lesser celandine is a menace, there's hope it can be stopped before it spreads to the creek.

For a fact sheet on this plant, go to: http://www.invasive.org/weedcd/pdfs/wgw/lessercelandine.pdf Note that the distribution map doesn't even show it as having spread yet to NC.