Perennial plants are a good investment. Plant once and have flowers that bloom for years. However, some plants that seem innocent take over the garden and quickly spiral out of control. Others bloom for such a short time that they don’t seem worth the trouble.
Whether they’re invasive, fast-spreading, short blooming, impossible to kill, or difficult to grow, the 30 perennials in this blog post are plants I’d rather not see in my Zone 3 garden. In fact, these perennials could be considered a beginner gardener’s worst nightmare!
If you want to see what an overgrown perennial garden looks like, check out the video below:
Disclaimer #1: Some of the plants in this list may not be problematic in your area. If you’re reading this and you live somewhere warmer, you might enjoy 50 More Perennials You’ll Regret Planting, a compilation of the perennials that have been disastrous for my readers gardening in other zones around the globe.
Disclaimer #2: Just because your favourite plant is on this list doesn’t mean it’s “bad” or shouldn’t be planted. This list is intended for beginner gardeners who aren’t able to keep up with these presumably low-maintence plants when they get out of hand. I want to spare beginner gardeners some heartache until they gain the knowledge and experience to keep up with more aggressive plants.
1. Lily of the Valley
Hated by experienced gardeners everywhere, it’s best to confine this one to a pot if you can.
Plant only if you like running around in circles trying to contain it.
I love Yarrow, especially for making floral arrangements all summer long. However, it will spread to your lawn and is very difficult to get out.
If you’ve read this blog for any amount of time, you know I really dislike Ferns. In 2018, I removed at least 100 Ostrich Ferns from our yard, and then in the following year, I pulled out another 218.
Yes, you read that correctly. 218 Ferns!
They look beautiful, but if you want to remove them it takes a lot of muscle power. I recommend using a hand-held garden tiller like this one.
Curious about what’s in my backyard? Check out what we started with and what we were able to grow in one year in our urban garden.
These were EVERYWHERE in my overgrown backyard in Saskatoon and they drove me crazy. However, I had decent luck keeping them under control after I dug most of them up.
Just don’t. Yes, they are pretty, but they’ll be out of control within 3 years.
7. Chinese Lanterns
I LOVED my Chinese Lanterns, but they slowly took over my lawn. The roots travel just below the surface, so, unfortunately, chemicals are the only way to get them under control.
Related: 6 Truths New Gardeners Need to Know
8. Bee Balm
This beautiful herb is so aggressive it will grow in gravel. That being said, I love growing Bee Balm in my cutting garden and would definitely recommend it to more experienced gardeners.
Related: 44 Pollinator-Friendly Flowers and Herbs to Help Save the Bees
9. Goat’s Beard
Any plant that resembles a Dandelion in full seed is probably not a good idea.
10. Purple coneflowers
Self-seeding and fast-spreading. Unless you have lots of goldfinches that will eat the seeds and keep them under control, don’t plant it.
Very useful as a natural cleaner, but can run wild if it has ideal growing conditions.
When a plant’s other name is Speedwell, you know it’s going to overtake your garden in short order.
Ground Cover perennials Gone Wild
A great solution for ground cover in a shaded area… until it takes over in 5 years.
Unless you want it as your lawn or have a horse to feed, don’t plant it.
15. Bishop’s Goutweed
While it works great for ground cover in a shaded area, you will never, ever get rid of it.
perennials best Kept for Container-gardening
Do you have a friend who is always trying to pawn off mint to you? This is why. If a plant has mint in its name, chances are it’s super invasive. Catmint and Lemon Mint, I’m looking at you.
Shamrocks are beautiful indoor container plants but become an invasive headache if planted outdoors.
18. Oriental Limelight
Cut back aggressively in June and DO NOT plant anywhere outside of a container.
the Too-Short-Blooming-for-the-Effort Perennials
Irises are so gorgeous, but it seems like they last for 2 days and then they’re done. They can also get out of control if not divided regularly.
There are many beautiful Daylilies, but the varieties I’ve grown seem to bloom for less than a week and take up a lot of space. If you plant the common orange one, it will take over your pretty specialty hybrid ones over the years. And that would be tragic!
Difficult-to-grow perennials in Saskatchewan
21. Any plant labelled Zone 4A or Higher
It doesn’t matter if you’re going to put it in a south-facing spot right against the house… It will die. Sometimes you can just scrape by if you mulch well enough, and often those who live in the southern-most areas of the province have greater success.
To everyone outside of Zone 3, enjoy your Zone 4A+ privilege. Nope… not bitter at all.
While not impossible to grow, especially if you choose a variety bred for the prairies, it is best left to more experienced gardeners.
23. Dahlias, Calla Lilies, or any other plant that you have to OVERwinter indoors
Unless you like that sort of thing. Carry on.
Update: Since I first wrote this post I have come to love this sort of thing. But I don’t recommend it if you’re brand new to gardening, as you likely will not remember to bring them in for the winter.
The Impossible-to-Kill perennials
When I was young my Dad dug out our rhubarb plant at least a foot and half down and sprayed it with round-up. It still came back. I personally like having a Rhubarb plant, but any more than one is excessive.
While the fruit is delicious, be prepared for your canes to spring up in unexpected places.
Hollyhocks only live for two or three years but are masters of reseeding themselves.
While super useful as a medicinal plant, Comfrey can take DECADES before it starts to decline.
28. Bachelor’s Button
Another prolific self-seeder. Save yourself the headache and plant the annual version from seed instead.
29. Virginia Creeper
The good news: it will grow in practically any light or soil condition. The bad news: it will grow in practically any light or soil condition.
Tansy can produce up to 150,000 seeds per plant and each seed remains viable for up to 15 years.
One gardener’s weed is another gardener’s favourite flower. If you really love any of these perennials, please don’t let this list stop you from planting them. You can always just embrace the overgrowth. But, if you do want my opinion on what to grow instead, check out these 57 must-grow perennials for Zone 3 gardeners.
Did I miss anything? I’d love to hear about your perennial gardening regrets. Find me on Facebook, Instagram, and YouTube for more cold-climate, short-season gardening tips!
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