Author: Admin

By Nan Brown, April 2023

An example for those in the Bruce County area is in Southampton where the spread from the old pioneer cemetery on the upper bank of the Saugeen River has taken over huge swathes of forest undergrowth. I walk through and feel overwhelmed and defeated from such mistakes of the past. 

One would think we could learn and prevent invasions such as this in the future. But no, garden centres are still selling periwinkle in nurseries in Ontario.

Here are some of my pictures I took of these areas in Southampton, Bruce County.  I like the last three pictures especially.  The last one shows one of the old bases of a tombstone with a view of the beautiful Saugeen river down below the cliff at this site very close to where it empties into Lake Huron. Around the base are not only periwinkle but also Lily of the Valley which also runs rampant in this area. The second last picture shows a sea of periwinkle surrounding the sole surviving native wildflower, a broad-leaved goldenrod. The third last photo shows the sea of dark green periwinkle from white birch to beech and maple sealing the forest floor in all directions.  One can’t see the vastness of this invasion from these photos however trust me it goes on for metres and metres deep into the forest and down the bank towards the river. Someday I will measure the extent it covers I am sure.

I was shocked when I first came across this area. For me, it exemplifies the need to educate people, especially gardeners, that the plants we choose now can have ramifications for years to come. Periwinkle, goutweed, Norway maple and so many other invasives should not be allowed anywhere near natural areas. If garden centres did what was right for the environment and stopped selling them, then maybe their followers, the gardeners, would listen.

This article is one of many stories we receive regarding invasive plants, the harm they do and the cost of removal in labour and time. This is a testimony to why invasive plants like periwinkle should not be sold.

The Perils of Periwinkle

by Anna Thomas. Republished with permission from the East Gwillimbury Gardeners newsletter April 2023.

When we moved into our house 25 years ago, there was a huge patch of periwinkle off the kitchen window.  At the time, I didn’t know it was invasive, but I wasn’t particularly fond of the plant and we wanted to regrade the area so not knowing any better, we turned it over and covered it with about 2-3 feet of soil.  Luckily, for us this killed off that area.  Unfortunately,  I didn’t remove it all and let it spread on the periphery.  At first it was a slow spread and so I didn’t worry about it much but occasionally pulled some out.  

Twenty five years later and it had spread beyond anything I could have imagined.  On our 7 acre property I found 5 very large areas growing about 100 feet from the house and into the forest.  Also, the area I left by the house had spread about 20 feet to the north and south of the original spot.  It was taking over other garden beds and strangling other plants.  Last December we went for a stroll around the periphery of our property and found another area on the alternate side of the property.  This was heartbreaking as I thought I had identified all the areas where it needed to be removed.  Obviously, this plant spreads not just by runners but also it seeds itself with the help of birds.

Over the last 3 years I have been removing periwinkle with a vengeance.  I’ve managed to clear the areas by the house which has allowed me to replant with a mixture of native and non native perennials.  In those areas there has been little to no regrowth.  If there are no plants you want to keep it’s fairly easy to pull out and then lightly fork over the area and remove the roots which are quite distinctive.  However, if you have an area with plants you want to keep you will need to dig up those plants, bare root them and pot up until you have the area cleared.  Under most circumstances, I would remove all that I can and then plant with annuals for a year.  If you can’t wait and need to replant, then you need to check on a regular basis and remove any stragglers that return.  Of all of the invasives, periwinkle is probably one of the easier to remove.

My preference for removal is to dig it out as the roots are fairly shallow and you see immediate results.  However, it is possible to solarize if you are willing to leave covered for a few years.  To do this it needs to be in a sunny area.  Damp down the area thoroughly and cover with clear plastic and ensure the plastic overlaps the edges of the periwinkle.  Hold down the edges with bricks or old logs.  This will kill everything under the plastic including any beneficial organisms in the soil and insects so this would be a last resort method in my opinion.  You can also cover with cardboard but when doing this it is best to clear the periphery and then make sure the cardboard overlaps the cleared area.  I’ve tried this in one area that was a bit more difficult to access and unfortunately I didn’t clear the periphery well enough and so I continue to get some escaping from under the cardboard.  Lesson learned!

Unfortunately, I’m still battling a large area in one of our meadows (it was originally about 12 x 30 feet but I’m down to the last 5 x 10 ft of periwinkle to remove) and another area under some cedar trees.  These areas are more difficult as the periwinkle is interspersed with other plants and roots.  It requires constant vigilance to remove any regrowth but I’m hoping that I can declare myself periwinkle free in 2023!

How to dispose of the periwinkle you have dug out?  Well, don’t put it in your regular composter for one!  You can put it out with yard waste but you can’t always be sure that the municipal compost facilities are hot enough to kill the periwinkle and you run the risk of it being given away to other unsuspecting gardeners.  Ideally, you would put it in a garbage bag in full sun for a few weeks to kill it.  After this time, it can be put out with your regular garbage.  I am lucky enough to have a dedicated bin that I use just for invasives.  It is a 4 x 4 bin that is contained so nothing can escape and I add all invasives to this bin, including garlic mustard, goutweed and lily of the valley.

Of utmost importance is to ensure that other gardeners are aware of the invasiveness of periwinkle and are warned against buying it or sharing plants.  There is hope that at some time in my life this and other invasive plants will be banned from being sold in the nursery trade as there are too many unsuspecting gardeners who are unaware of its invasive properties.

Sault Ste. Marie—Gardeners and property owners in Sault Ste. Marie and Algoma District now have access to a “grow me instead” guide geared to this area. Produced by local environmental group Clean North, this guide spotlights 24 invasive plants known to be aggressive invaders here. It also suggests native plants to grow instead.

Replacing invasives with natives can be a big job, but it’s also rewarding. “I have greatly increased the number of native plants in my yard over the past decade, and the increase in biodiversity—especially pollinators—fills me with joy,” says Abby Obenchain, Clean North communications lead and author of the new guide. “I hope the new Grow Me Instead Guide will help others find the same joy.”

She points out that invasive plants pose a major threat to biodiversity. “They can push out native species and dominate ecosystems, reducing food sources and habitat for wildlife. They also can cause harm to the economy, recreation, and even human health.”

This guide came about because for years Obenchain has observed invasive plants wreaking havoc in her own yard as well as in natural areas in and around Sault Ste. Marie. 

On behalf of Clean North, she applied for and won a $1,000 Invasive Species microgrant to develop an invasive plant education program for the Sault/Algoma. The Grow Me Instead Guide is the flagship product. 

To complete the guide, she set out to determine which species were most troublesome locally—and which native plant species make the best alternatives. This work included consulting with partner organizations (listed below) and local botanists.

The end result is available on the Clean North website at cleannorth.org.

So what advice does Obenchain have for gardeners who want to tackle invasive plants on their property? “The first step is to inventory what plants are growing in your yard,” she says. “Then figure out which are invasive—spreading rapidly is a good clue; prioritize which to remove first; and replace them with native alternatives.”

She acknowledges that finding native plants can be a challenge. “They do pop up in local garden centres, but gardeners should double-check whether a plant is truly native before they acquire it. I’ve discovered that many plants people think are native here are actually not.”

Because of these challenges, the Sault/Algoma Grow Me Instead Guide has a unique feature: It offers two types of alternatives to invasives. One group comprises plants native to Algoma and the other features plants native to other parts of the province. 

“Plants in the second category are still familiar to and offer benefits to many native pollinators, birds, and other wildlife,” Obenchain notes. “And they give people a bit more flexibility as they try to be more eco-friendly gardeners.” 

Clean North would like to thank the Invasive Species Centre and Bruce Station Horticultural Society for providing funding for this work. Project partners/supporters are: 

• Sault Naturalists
• The Kensington Conservancy
• Sault College School of Natural Environment
• Sault Ste. Marie Region Conservation Authority
• City of Sault Ste. Marie § Lake Superior Watershed Conservancy
• Bruce Station, St. Joseph Island, and Sault Ste. Marie horticultural societies
• Seedy Saturday Algoma § Algoma Master Gardeners
• Johnson Farmers Market

For more information about replacing invasive species with native plants, visit cleannorth.org or email Clean North at info@cleannorth.org.