Arlington, MA Invasives "ArMI" Army's Boletim

Japanese hops (Humulus japonicus) are the new invasive weed in town. They are an annual vine with palmate leaves which have 5-7 lobes, and look a little like a Virginia creeper. It's easy to tell the difference though; Japanese hops have hooked hairs or barbs along the leaves and stem. If you try to brush past one, it will grab you, and if you try to pull one, wear gloves and sleeves. My forearms are covered in welts from the 5 minutes of vine removal before I got adequate protection.

This plant has spread from several sites around the Northeast, but it hasn't been around Arlington until this summer. A couple moved into the neighborhood last fall, and decided to remove the front lawn and plant for pollinators. They went to a wonderful local garden center which stocks native plants (Mahoney's) and bought some pollinator and hummingbird seed mix from Earth Science brand. Unfortunately, that seed mix was contaminated with Japanese hops.

I watched their wildflowers come in this spring, and this summer I noticed the vine taking over their pollinator meadow. Unfortunately I didn't identify it until after I found a plant in my yard. In one season, the vines took over their whole front yard, their shrubs, and climbed higher than I could reach (while standing on a chair) up their Kousa dogwood. On top of that, in this one season it produced seeds which spread to my yard on the wind, and the plant in my yard was already flowering when I found it. That is scary.

Our new neighbors were on board with the removal, after I explained what the vine was. They helped me for hours in the hot sun, and gave me lots of seltzer water. We removed the plants, and tried to carefully bag all of the seed-heads, and they will keep an eye our for more. There will be more, and not just in their yard; I expect it will be all around the area near Scituate Street, between Grey St. and Mass Ave. There were lots of seeds, which spread on the wind before we started removing it, and we probably disturbed and spread some while removing the vines.

I wanted all of you to know about it, because I need people to help keep an eye our for me. I will be moving to Acton in October (2022) and though I plan on coming back to check, it only takes one missed plant to spread further. I really hope that the spread stops with the area around Scituate Street and Mnt. Vernon. These nasty vines can grow 35 feet in a season, and start producing spikes of white flowers after only a few weeks. They also kill other plants with allelopathic (soil chemistry) effects [1,2]. Never have I ever seen a vine that could take over shrubs and meadows as quickly as Japanese hops do here.

[1] https://extension.umass.edu/landscape/weeds/humulus-japonicus
[2] https://www.invasive.org/browse/subinfo.cfm?sub=10091

P.S. On top of all the awful things this vine can do to the ecosystem, it can also do some pretty uncomfortable things to you. Wear protection. It seems harmless and easy to pull, if a bit prickly, but those welts it gave me burned for hours. Wear a mask if you have allergies; apparently it is a moderate allergen, but it uses wind-pollination, so it produces a profusion that will puff up into the air as you pull the vine.

Hill’s Hill is a small wooded hill in Arlington sandwiched between lower Washington St. and a Park and Rec Department soccer field. In a shadier portion at the top, black swallow-wort (BSW) took hold some years back and spread, blanketing oak and hickory seedlings and blocking access to light. The Invasives ArMI chose this site for BSW removal and eventual renewal with native replacements. We are happy to report that the previously overrun tree seedlings have survived. https://www.inaturalist.org/observations/84479644

As we've worked each week on the Hill this summer, we gradually noticed its valuable assets, delineated here: https://drive.google.com/file/d/13Se57e89x_TuL9jtBZkkVxH9XhMPibNj/view?usp=sharing

By traditional standards for measuring old growth forests —a measure of girth at chest height (DBH)— Hill’s Hill does not compare with a large forest. But then Arlington is not in the middle of Maine either. We have to value what we have.

The value of an ecosystem goes beyond the number of mature trees. It includes its future potential, and the variety of species supported right now.

Numerous tree seedlings and saplings at Hill’s Hill, such as oak ( https://www.inaturalist.org/observations/135167983 ), cherry (top 2), aspen-poplar, and hickory, contribute to its future potential. Anything growing right now has already found a nourishing spot with the right mix of sun, soil, and water. Just because it’s little doesn’t mean we shouldn’t protect it. The root systems of these naturally sprouted trees have perhaps more value than what we see above ground... it's what's going to help these trees survive during a drought like the one just experienced, whereas a planted "replacement" tree will more likely die.

High value current habitat can be measured by the numbers of species supported. Trees, being large, tend to support the most. But certain shrubs are numbered among the top Keystone plants. For example, blueberry is the only shrub genus to make it into the top 10 Trees & Shrubs (at number 7) as researched by Doug Tallamy, entomologist at University of Delaware. Keystone plants support the pollinator/caterpillar base of Arlington's ecosystem. According to this zip-code-specific National Wildlife Federation database ( https://www.nwf.org/NativePlantFinder/Plants ), the genus Vaccinium (blueberries, cranberries) hosts a whopping 282 soft-bodied caterpillars and other insect larva that birds in Arlington depend on to feed their babies.

Fortunately, there's a substantial blueberry patch at Hill's Hill protecting a down slope at the edge of the meadow from erosion. ( https://www.inaturalist.org/observations/133465271 ) We can add this asset to the sumacs anchoring the remaining meadow edge. ( https://www.inaturalist.org/observations/127432733 ) And the blackberry patch that John Eastman (Forest and Thicket) characterizes as a natural tree nursery. (https://www.inaturalist.org/observations/127433059 )

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The National Wildlife Federation explains the importance of Keystone species, and offers a general list of Keystone Native Plants in the Eastern Temperate Region.
• "Native plants have formed symbiotic relationships with native wildlife over millions of years, creates the most productive and sustainable wildlife habitat.
• "Keystone plant genera are unique to local food webs within eco-regions. Remove keystone plants and the diversity and abundance of many essential insect species, which 96% of terrestrial birds rely on for food sources, will be diminished. The ecosystem collapses in a similar way that the removal of the “key” stone in ancient Roman arch will trigger its demise."

National Wildlife Federation Keystone (NWF) dbase by zipcode: https://www.nwf.org/NativePlantFinder/Plants

NWF Keystone pdf: https://www.nwf.org/-/media/Documents/PDFs/Garden-for-Wildlife/Keystone-Plants/NWF-GFW-keystone-plant-list-ecoregion-8-eastern-temperate-forests.ashx?la=en&hash=1E180E2E5F2B06EB9ADF28882353B3BC7B3B247D