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As a Cambridge real estate agent, the city squares of Cambridge, Somerville and Medford and the town centers of Arlington, Watertown and Belmont, Massachusetts are my home turf. And as a lifelong New Englander who’s lived within twenty miles of Boston most of my life, I can introduce you to other nearby towns as we search for your new home. If you’re planning to sell your home in Cambridge, MA or nearby you’ll find plenty of info about the home selling process here too. Questions? Send me an email or call me at 617-504-1737.

Black Swallowwort is Invading Cambridge

swallowwort-in-CambridgeMy nemesis – black swallowwort – is popping up all over Cambridge.  I’ve been out and about in the last few days and found patches of it in many front yards in Cambridge. And no question about it – it’s in Somerville, Medford, and Arlington too.  In fact, it’s becoming an issue all over Massachusetts.

Black swallowwort looks a bit like milkweed.  But instead of the fuzzy, lumpy pods of regular milkweed the swallowwort seed pods are thinner and smooth, shiny green.  It’s a rapidly growing vine and if allowed to flourish will produce numerous pods. Last summer I would find large stands of swallow-wort covering chain link fences and dripping with pods.  Unfortunately I think some people actually like it since it does do a good job of covering up those chain link fences.

I found black swallowwort in my yard a couple of years ago but didn’t know what it was at the time.  But it was growing so fast – twining around other plants, sprouting up everywhere I looked – that I searched online for it.  I was horrified by what I learned.  Search for it online and you’ll be ready for all out war after you learn more about it.

Black swallowwort is extremely invasive.  It will push out other vegetation and is hard to eradicate.  Like regular milkweed, the seeds from pods that are allowed to remain on the vines will spread all over the neighborhood.  Your neighbor’s swallowwort is your problem too.   Let it thrive and soon it will be all over the neighborhood pushing out other plants. 

Swallowwort is not only a threat to vegetation – it is also believed to threaten the viability of monarch butterflies.  Monarchs lay their eggs on milkweed and are thought to mistake swallowwort for milkweed.  Caterpillars hatched on swallow-wort do not survive however.

The first year I found this invader in my yard I made the mistake of breaking off the vines but leaving them to wither with the pods still attached.  Unfortunately, even if the vine is dead, the pods will still eventually release their seeds.  The pods must be removed and disposed of carefully – I wrapped them up in foil or tightly closed bags. Some recommend burning.

Last year I went on an anti-swallowwort crusade.  Anywhere I went I would pull off pods and filled bags with them.  I listed a house for sale in Cambridge that had black swallowwort climbing everywhere in the garden.  I filled trash bags with the vines.  Once I started to look I found it everywhere – all over Cambridge, Somerville, Medford and Arlington. 

I’ll post more photos of swallowwort as it matures.  The picture taken above was taken in Cambridge in mid-May.  Right now the pods aren’t out but the flowers are on the vine. The flowers are small and purple. The leaves are spade shaped and shiny green – sort of like lilac leaves but shinier.  The way the vine will curl around whatever it comes in contact with is very distinctive.

If you see pods when you’re out and about – pick them and dispose of them.  If you discover swallowwort in your yard the only effective method of eradication is repeated sprayings of herbicide.  Pulling the vines will not work – there is a large underground network of roots and you can’t stay ahead of it by pulling it.  Get an industrial sized bottle of herbicide and get ready to do battle.

Categories: Living Here

  1. Marie

    I am so happy to find a fellow warrior!!! I love the clarity and style of your posting. Much better probably than my house by house approach: I have been leafletting in my neiborhood about it without much success, trying to convince people to deal with it, even helping them doing it in cases. I am concerned about the use of herbicide. Does it damage other plants? How do you apply it? What brand? When did you start that method? Does it guarantee long term eradication? I have not dared recommend it because if used improperly, I think it is not healthy… Also I spent so much time pulling, digging out ect, I got a poison ivy like rash. Is that unusual?

  2. Elizabeth Bolton

    Hi Marie,

    So nice to hear from another fighter for the cause! And it’s funny – just this afternoon as we were passing large swallowwort vines covered with pods in Cambridgeport I mentioned to my mother that next year I was going to start leafletting. I’m going to print a stack and keep them with me from spring through fall.

    My theory about the rash is that the plant seems to be more potent as it matures. I had no problem with it early in the spring but as the vines got more full and the pods came out I developed what I called “swallowwort hand” – a bad rash right on the finger that grasped the vines – I try to pull them out whenever I spot them. It got so bad that I carried plastic bags to put on my hands – and more to fill with pods. I still get tempted to pull the vines with my bare hands but I usually kick myself when I have to bandage that finger again.

    Re weed killer – I poked around online and most references I found recommended Roundup – and I think one other whose name escapes me. I’ve been a fan of Roundup since I used it to successfully vanquish some bamboo that had even sprouted inside the ell of my first old house – that was a monster of a plant and I was delighted to finally get rid of it. I’m no expert on herbicides but have read things that suggest Roundup is fairly innocuous and breaks down pretty quickly. If you’re concerned you would probably want to read up on it – it was worth it to me but I know some people don’t like to use chemicals. It will kill other things that the spray falls on so for the swallow wort I was putting some in a container and painting it on with a paint brush. It doesn’t take care of all of it the first season but it makes a huge dent – you can win but you have to be persistent.

    Great to know somebody else is out there spreading the word. The cause endures!


  3. Marie

    thanks so much for replying! Now that spring is here, I am thinking of having free local publications, from the city of Cambridge, or Cambridgetab, have articles warning people about Swallowwort. Or in the garden column of the Boston Globe. Also have leaflets handy at local nurseries. I am not good with a computer (that is why it took so long for me to read your reply to my post. I had completely milplaced the reference until today, months later!) Would you have pointers on how to make a good leaflet with a photo of Swallowort at the various stages that people must watch out for: seedling, as well as the later stages.

  4. wolf

    i live one state over-and i absolutely HATE this stuff.
    my neighbors don’t remove theirs so it keeps drifting back.
    i agree,burn the pods!!

  5. Kate Wheeler

    I just did half an hour of guerrilla Swallowwort weeding on Bishop Allen Drive, which is a block north of Mass Ave between Inman and Prospect Streets. Further help would be appreciated!

    Unfortunately, I didn’t have a good digging implement and couldn’t get all the roots, so I just attacked the vines and left them on the sidewalk, but I think I did prevent some of them from flowering.

    There is a big infestation all along that block, in the unkempt flowerbeds of several apartment buildings.


    Bonny’s Garden Center near Fresh Pond is handing out color Xeroxes, which is really great. I support Bonny’s, a multi generational, locally owned plant business

  6. Wendy Cook

    Thank you Elizabeth. I read Kate’s FB status and followed the link. Lo and behold, this is the vine that i suspected was an invader! Happy to have confirmation. At the Kurukulla Buddhist Center in Medford it is all along the chain fence at the back of the property. I really don’t like to use chemicals. But sometimes I do. Poison ivy is exempt from mercy. I’m adding Swallowwort to “have no mercy.”

    ps. I’m a fan of Bonny’s too.

  7. Michael Perna

    I too, have become a soldier in this war and fighting on the NY front. I have found that mowing does not eliminate this weed, which has a life span of 50 years. Digging as the soon as the plants appear works but can only be done on small patches.

    From my perspective (having 50 acres), with patches throughout, I have found that Roundup Pro works best and at the lowest cost. The problem is compounded by the bank of seeds that have built up prior to knowing how to fight this. Over the last 3 years, it seems I am able to reduce each year by 80%. Hopefully, the weed will continue to be responsive to Roundup. Any small patches are best removed by digging. NOTE, only the removal of the plant crown (within 2 inches of the surface) seems to kill the plant.

  8. Elizabeth Bolton

    Great to hear that you’re fighting the good fight Michael! I too am a fan of Round Up. 50 acres – yowza! That’s a lot of pods. And thanks for the lifespan info – I hadn’t heard that. In my little yard I can keep it at bay by being vigilant about breaking off the vines and never letting pods form. But I use plenty of Round Up too – I go around with a paint brush. Good luck with it.


  9. Amanda

    On my own property I started with some ineffectual pulling and then started more seriously digging out the rizhome. I will do this method as first response where I can. Then in my concrete driveway when they come up, I will consider herbicide. Digging these out is hard. It takes a lot of time and patience. And when I first moved in my priority was to at least keep existing plants from producing seeds.

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