Old Ottawa South Community Association

Garlic Mustard. Photo by Christine Hanrahan.
Garlic Mustard. Photo by Christine Hanrahan.

Invaders in your Garden

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“Invasive” is a word used to describe any plant or animal that is growing or multiplying to the point of driving out other species. It’s out of control. It’s not in balance with the rest of the plants and creatures in its ecosystem. An invasive species can be native, but it’s most often non-native. But just because a plant is not native, doesn’t mean it’s invasive. Most of the horticultural varieties in our gardens are non-native, but they behave themselves and don’t spread all over your yard. They are not invasive.

However, there are some very invasive species in Old Ottawa South, and you should know about them.

Dog-strangling Vine
Mass of Dog-strangling Vine in flower. Photo by Christine Hanrahan.

Dog-strangling Vine or Pale Swallow-wort (Vincetoxicum rossicum) is one of the most difficult-to-control invasives and it’s popping up in many gardens in our neighbourhood and parks. Google Dog-strangling Vine and you’ll find many photos of it at all stages. When it blooms, it has tiny, dark reddish flowers are found at the top of a twining stem. As seeds start to form, in thin pods, like milkweed, the stems bend over and twist together. Try to walk through it and you’ll immediately understand the reason for its common name.

If you find one or several plants in your garden, dig it out immediately. It’s important to remove the root crown – that’s the place where all the roots and shoots grow from. It’s not necessary to get all the little pieces of root; they won’t regrow. If you can remove the crown, the plant will be gone.

If you have a whole field of DSV on your property — or as you’ll find at Brewer Park — getting rid of it is a multi-year project. If the patch is small enough, cover it with a heavy tarpaulin (landscape cloth does NOT work), and leave it in place for 2 years. If you’re dealing with a whole field of DSV, use a tarpaulin on one area, then cut the rest using a scythe or weed whipper and do this several times to prevent the plants from going to seed.

Dog-strangling vine in seed. Photo by Kathy Krywicki.

DSV multiplies only by seed. The existing plants do not grow new ones from roots. If you can stop seeds from forming, no new plants will appear and you can slowly deal with the existing ones.

More information is available on the Fletcher Wildlife Garden (FWG) web site, including control methods based on experience and a fact sheet in French and English. Just Google: Fletcher Wildlife Garden Dog-strangling vine.

Garlic Mustard
Garlic Mustard.

Although not native, most members of the mustard family are very beneficial. They include mustard, of course, but also broccoli, cauliflower, brussel sprouts, and many other food crops. Many might be considered invasive, but Garlic Mustard (Alliaria petiolata) is a particular problem because it can grow in shade. Its roots also produce chemicals that destroy the mycorrhizae that many trees depend on to transport nutrients through the soil.

Garlic Mustard is a biennial – it grows a lot of leaves the first year, then flowers the second year and then dies. Good news! However, the seeds it produces in that second year can remain dormant but viable in the soil for many years and pop up just when you think you’ve eliminated it from your garden. So, it’s important to pull out this plant before or while it’s flowering to prevent it from releasing seeds. It’s also important to put the plants into a garbage bag because they can continue seed production even after they’ve been pulled out of the ground.

The FWG also has more information about Garlic Mustard as well as a fact sheet. Just Google: Fletcher Wildlife Garden Garlic mustard.

Other invasives

I wanted to tell you about DSV and Garlic Mustard because they are showing up in our gardens. However, there are other invasive species in our neighbourhood that are causing problems and spreading rapidly in some areas. As the Enviro Crew works to introduce more native species into the Brewer Pond area, and later other neighbourhood parks, we hope some of you will help with invasives control.

Other invasives in our area include: Common Burdock (Arctum minus), Jerusalem Artichoke (Helianthus tuberosus), Elecampane (Inula racemosa), Comfrey (Symphytum officinale), Common and Glossy Buckthorn (Rhamnus cathartica and R. frangula), Japanese Knotweed (Reynoutria japonica), Creeping Bellflower (Campanula rapunculoides).

If you have any questions about any of these species – or want to add to the list – please feel free to get in touch with us on Facebook (Enviro Crew of Old Ottawa South) or by emailing envirocrewoos@gmail.com

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