Text by Kit Britton; photos by Jim Bly, unless otherwise noted. 

The February 26 Italian arum eradication event at the grounds of Culpepper Garden senior living community was the kickoff of a stewardship activity to last one year. A plant that was likely spread to the site as an escaped houseplant, in the root ball of a purchased plant, or by bird transmission of seed has turned into an ecological nightmare.

What is Italian Arum and Why is it a Problem?

Italian arum (Arum italica) is an ornamental plant that was brought to North America because of its attractive winter foliage and orange berries. It has been listed as a “dirty dozen” plant in Virginia can spread quickly to nearby areas and can outcompete native plants. It can be spread further by birds that eat and disperse its seeds. Arum has orange-red berries that grow in oblong clusters and can be toxic to both humans and wildlife. Its flowers emit an unpleasant odor, and its oils are a known skin irritant. Even with all these negatives, it is still commonly sold in the horticulture trade as both a houseplant and a landscaping plant.

Sightings of this plant in Arlington vary. Some are found on the margins of parks near houses and gardens and in backyards and neighborhood vacant lots, but they also appear in parks far from potential backyard origination points. Unfortunately, once Italian arum takes root, it can become quite dense. 

At Culpepper Garden, staff and residents were horrified to discover the potential damage this spreading invasive could do to this iconic 5-acre site. As a resident of the community and ARMN member, I suggested that we contact Jennifer Soles, Invasive Species Coordinator of Arlington’s Department of Parks and Recreation. Once she investigated the situation, she developed a protocol for eradicating the Italian arum from the location.

At Culpepper Garden, the Italian arum plants were more widely spaced than in many places, making their removal easier. Using Jennifer Soles’ directions, we dug up each plant with its surrounding soil, lifted the whole mass carefully into bags, and marked the holes from which the plants had been removed with red flags for a one-year measurement of outcomes included in the project design. It took 11 volunteer Master Naturalists, community volunteers, and resident volunteers about three hours to dig up and bag 36 plants found in four distinct areas of infestation. 

Later, Culpepper Garden grounds maintenance staff picked up the tied bags and carefully transported them to the trash dumpster for treatment as trash (not compost, which could spread their seeds).

This project is coming at the right time because it may add information about control options at a time when Italian arum infestations are on the rise—not only at Culpepper Garden but in area private properties and public spaces where ARMN park stewards work. (Park stewards are Adopt-a-Park leaders who oversee volunteer stewardship work in Arlington, Alexandria, and Falls Church parks and engage with neighboring park communities.) And there is still time to dig up the plants prior to their 2023 seed production.

How Does the Italian Arum Spread?

Arum italica has two methods by which it propagates and spreads. First, the above ground foliage grows from an underground tuber or bulb; the tubers propagate by forming multiple bulblets or daughter tubers, which separate and produce new stems. As the tubers spread laterally, Italian arum spreads. Sometimes, small plants can be eradicated by digging out all plant parts and tubers.  

The second method of propagation occurs when the plant flowers in the spring and summer and produces heavy seeds that drop onto the ground below or not far away. Wind cannot carry these seeds, but water flow can. And birds eat and spread the seeds.

The seeds themselves form a “transient” seed bank with less than one year of viability; not a “persistent” seed bank with seeds viable for more than one growing season.  Despite the transitory nature of the seeds, the next step in the reproductive cycle from seed is formation of a tuber that stays dormant for two years. So, there is effectively a three-year lurking danger from underground: one year as viable seeds and two years afterwards as dormant tubers. On the Culpepper site, seeds dropped by plants in summer 2022—as well as seeds up to two years older than that—can germinate plants now.

So, How Can We Get Rid of Italian Arum Once and For All?

In January, Master Naturalists exchanged strategies to eradicate Italian arum from their parks and neighborhoods, and after spirited discussion, the consensus was that digging and removing all plant material and more dirt than one might think necessary is needed to dispense with both dormant bulblets and the stubborn seedbank lurking in the soil. 

In addition, for resilient plants like this Italian arum, Master Naturalists wondered if chemical treatment would be an effective long-term solution. The problem is that only complicated chemical mixes may work, and these are beyond the reach of typical homeowners. This solution was also nixed by the Washington State Noxious Weed Control Board (a state where this invasive plant is rampant). There has been no consistently reported success with any chemical mix. With that, the Noxious Weed Control Board confirmed that manual methods including deep digging are the way to go. So, the Master Naturalists are sticking with manual removal, too.

The Plan for Culpepper Garden

We decided to monitor the holes left behind from which the arum was pulled and the broader infestation areas on a weekly basis and note any new growth. Italian arum plants found will be removed immediately. Weekly removals will ensure that we get the plants out when they’re very small. Removals at or near the holes will hopefully provide data to evaluate and refine the eradication protocol. The admittedly optimistic scenario of no regrowth in and around the holes would indicate that we successfully removed dormant seeds and tubers. Some regrowth but less than at a distance in the broader infestation areas could indicate that we need to dig deeper. Also, if the plant doesn’t appear at or near the holes but does show up at a distance in the broader infestation areas, perhaps we are dealing with bird transmission or other forms of transmission.

The project will end on Feb 16, 2024, when the one-year monitoring period is over, after which we will use the data we gathered to refine protocols for future Italian arum eradication. 

Normally, ARMN volunteers only work in parks or other natural areas rather than private properties. While Culpepper Garden is private property, it has been designated as “Private Property of Special Ecological Significance.”  As such, ARMN volunteers may work here on invasive plant removal projects.

Text and photos by Devin Reese, except as noted.

I joined a group of volunteers recently who were getting ready to attack exotic invasive plants on the banks of Lubber Run stream. The site—Woodlawn Park—is a small park tucked into a residential neighborhood in Arlington. Perhaps its diminutive size explains how well its invasive plants are being addressed, or perhaps it should be credited to the enthusiasm and dedication of its volunteers.

Beth Kiser is the volunteer ARMN Park Steward for Woodlawn Park and the lead for the ARMN Park Stewards Program. (Park Stewards are Adopt-a-Park leaders who oversee volunteer stewardship work in Arlington, Alexandria, and Falls Church parks and engage with neighboring park communities.) Beth said that she is about five years into organizing volunteer work in Woodlawn Park and that, thanks to a cadre of regular monthly volunteers and support and coordination from Arlington County staff, the site has gradually transformed. 

Another neighborhood volunteer explains that “We’ve been working for a long time on removing the bush honeysuckle.” According to the Virginia Department of Conservation and Recreation, “Bush honeysuckles can rapidly invade and overtake a site, forming a dense shrub layer that interferes with
the life cycles of many native woody and herbaceous plants.” Today, the group is equipped with a Weed Wrench to wrest any bush honeysuckle (Lonicera spp.) out by the roots without disturbing the soil. Watching another volunteer tackle a different invasive plant, porcelain-berry vine (Ampelopsis brevipedunculata), a volunteer laments that, “It’s so evil. Porcelain-berry deserves more [removal] attention.” Like the bush honeysuckle, porcelain-berry can outcompete native plants for water and nutrients. 

Volunteer Curt is working to get the porcelain-berry vine out complete with its roots. “Wow, it does have a huge root. It’s going so far back. Is that normal for porcelain-berry?” As Curt remarks that he’s pretty new to this invasives work and needs people pointing stuff out, Beth shows him how to use the Seek app to help identify plants. The app is a companion to iNaturalist, the online social network of naturalists, citizen scientists, and biologists who create and share biodiversity information about plants, animals, and other organisms to help people learn about nature. However, Seek is designed to be more youth-friendly by including live AI-based identification using phone camera video as an input. Curt and Beth quickly corroborate that another plant he has removed is a type of privet.  

This is Curt’s first month of volunteering for naturalist habitat restoration projects, and he hopes to get to join the next ARMN training course. He has long been interested in the natural world and would love to improve his skills in identifying organisms, birds in particular. Curt also works as the Smithsonian’s National Museum of Natural History in the paleontology curatorial department. “I work with dead things at the Smithsonian,” he explains. So, this is his chance to work with living things. 

Becky Hamm is a member of the most recent ARMN cohort and volunteering at Woodlawn Park for the first time. Her inspiration to become a Master Naturalist came from living in a place with no outdoor space of her own during the pandemic. Her job in data analytics keeps her indoors. When she moved to a rental place with a yard, she wanted to create something other than a mowed patch; thus, began her exploration of native plants. Becky marvels at a native black locust tree (Robinia pseudoacacia) growing streamside, recognizing its distinctive paired spines, i.e., “big old thorns.”

Meanwhile, one of Beth’s regular volunteers is working at the south end of the park. Joao lives a stone’s throw from where he’s removing invasives and has been interested in tending the park since the beginning of Beth’s stewardship program. He waxes poetic about how the program has boosted the number of “beautiful, wonderful birds that come and sing,” including an owl that he recently heard “mewing like a child.” He comes out in the evenings to enjoy nature at dusk. Joao explains that he grew up on Madeira Island, Portugal, in a setting with an abundance of colorful flowers. He returns regularly to Portugal, but also appreciates the Virginia nature right here in his front yard. 

Beth explains that regular, community volunteers like Joao have helped gradually change the park to a wilder space. “It’s looking pretty clean” of invasives, she says, “and I credit all those folks who’ve been coming for a few years now even during the pandemic,” as well as support from Arlington County staff, who provide input on invasive management approaches. Where resources permit, they also arrange for carefully targeted spot treatments of herbicides to address invasives that volunteers can’t remove by hand. This partnership has proven essential, she says, in having lasting impact in restoring the area’s natural spaces and keeping up volunteers’ engagement in the work without getting discouraged.

In the five years of her supporting the park and the ARMN Park Stewards program, Beth is most excited about the native species that pop their heads up through the leaf litter now that there is clear space for them to grow back from seedlings or from dormant seeds in the soil bed. Thanks to getting invasives out of the way, she now sees native plants like wild ageratum (Conoclinium coelestinum), asters (family Asteraceae), native black cherries (Prunus serotina.), hollies (Ilex spp.), tuliptrees (Liriodendron tulipifera), American sycamore (Platanus occidentalis), American persimmon (Diospyros virginiana), and a few oaks (family Quercus). The native plants in the park appear to be part of two distinct remnant ecological communities that Beth describes as “floodplain forest” and “possibly mesic mixed hardwood,” respectively, pointing to the floodplain area where there are American elms (Ulmus americana), boxelder (Acer negundo), and remnant green ash (Fraxinus pennsylvanica), which is amazing for this small patch of a park.

In some harder-to-access areas in the park, invasives continue to take root. For example, English ivy blankets exposed tree roots in the steep slopes of Lubber Run that get less volunteer attention due to limited access. A volunteer says “Ivy is so evil. I don’t trust it. I always give personalities to the most invasive plants.” By her metric, we are wrestling with a lot of evil plant personalities as we pull, cut, and chop up. In the winter, with most of the plants not in their seeding stage, we can either chop them up and leave them on the ground to add to the valuable forest floor covering, or we can hang them up higher on branches. Beth talks about how people often remove the leaf duff (litter) from the ground, even though it harbors beneficial insects such as butterfly larvae and fireflies, microbes, and nutrients. Allowing the leaves to stay in place over winter can help these insects to thrive.

Eventually, ARMN volunteer Hal Cardwell climbs down into the stream valley with Beth’s specialized shovel (which she in turn had learned about from another neighborhood volunteer). Capitalizing on its serrated edges, he’s able to extract several well-anchored privets from the soil. A few slices and the privets are out!

Even as the group wraps up for the day, we find a few more opportunities for restoration. Curt spots a flowering plant on the streambank near where we started our work, and Beth excitedly says “Get it. That’s a Rose of Sharon with seed pods!” Indeed, this invasive’s fluffy brown flowers taunt us from their skinny stalks. Curt reaches down and gingerly pulls the Rose of Sharon (Hibiscus syriacus) out, careful to include the whole tap root. Right at our feet, Becky finds an errant Oriental False Hawksbeard plant (Youngia japonica) anchored to the ground. “It’s really aggressive,” says Beth, as Beth lays it—conquered—on a rock. 

Even at such a well-tended site, there are no shortage of opportunities for volunteers to battle invasives and improve its ecological quality through native plant regeneration. As we clean up, Beth tells us about the fireflies (Photinus pyralis)—an indicator of ecosystem health—that blink in the restored riparian vegetation along the stream during the warm months, and attract community members to gather and celebrate them together one night each June. The work today that helped to preserve a home for these beloved creatures was indeed well worth it.

Wildlife (All forms of life that are wild, including plants, animals, and microorganism – Natural Resources Service) 

Black Locust (Robinia pseudoacacia) Black locust, considered invasive in some states, is native to eastern North America from Pennsylvania to as far south as Georgia. When British colonists encountered the plant in 1607, they recognized its resemblance to Old World Locust and named it accordingly. A member of the pea family with pairs of round leaflets on spiny branches, black locusts improve soil quality by fixing nitrogen at their roots. The black locust produces fragrant white flowers with copious nectar that attracts native bee species, hummingbirds, and butterflies. Although toxic to some livestock, black locust provides habitat for native wildlife, including nesting songbirds and foraging deer. Learn more about black locust here.

Text, photo, and video by Nora Palmatier

In late January, ten volunteers met at Lacey Woods Park in Arlington to remove English ivy and porcelain berry vines from the edge of the managed area next to the forest. This is an area we’ve long neglected in favor of the natural area in middle of park. On this day, we removed vines covering a grove where there used to be houses with non-native azaleas, saucer magnolias, and rhododendrons. Then we noticed a 6″ DBH (diameter at breast height) “tree trunk” bent over, which after following its path through the rhoddies, realized it was a native grape vine—a rarity in Lacey Woods Park. We’ve only found one other back in the park’s thickest section of greenbrier (Smilax roundifolia). The photo below doesn’t do it justice, but the yellow line shows the vine’s path as it winds thru the rhoddies, over a holly tree (Ilex opaca), and up the limbs of the Eastern hemlock (Tsuga canadensis). Given that woolly adelgid have decimated so many hemlocks, finding one showing no damage from this insect was a find in and of itself! (And the red line was a first attempt that refused to be deleted.) 

Here also is a video of the vine: https://1drv.ms/v/s!AvAGQhg3_2eBgd0rPrnr_ZxgWapepw?e=830q4Q. But even that doesn’t show its 60-foot length. 

I returned the next day and discovered there is an auxiliary branch of the vine roaming over a stump that appears to have had grapes this year. Definitely, this will be explored during the summer when I hope to taste a native grape before they’re all gone to the birds.

I also posted news of the grape vine’s discovery on the ARMN and Tree Stewards of Arlington and Alexandria listservs and received the following comments:

1. Reminder to NEVER cut a vine until you have a positive ID that it’s an invasive and not a valued rarely seen native. We can always return and remove an invasive, but we can’t glue a cut vine back together.
2. Those wanting native vines in their own yards need to research the growth patterns and best locations. As Plant NOVA Natives states, “Right Plant, Right Place.”
3. Total Awe that such a treasure was only now discovered when so many of us have traipsed Lacey Woods Park the past decade for bird watching, tree walks, and invasive removal workdays.

A grape reminder that natural treasures exist even in the managed landscape. (Pun intended.) If you come to our next workday on Feb. 18, 2-4 pm, we’ll be happy to show you. Sign up at https://www.trackitforward.com/site/397421/event/786829. Bring your binoculars and we can argue about where exactly the vine ends….

For additional information on wild grapes, check out Alonso Abugattas’s blog piece: http://capitalnaturalist.blogspot.com/2016/11/wild-grapes.html; see also the National Capital Region