Be on the watch for Japanese Hops

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.

Posted on 06 de setembro de 2022, 11:33 PM by efputzig