Invaders I wish I’d never planted

This is not a picture of a spring garden. No, it’s a stand-off between the Hatfields and McCoys, with Prokofiev’s ominous Dance of the Knights as the sound-track. To the left, the Hatfields, wearing purple. To the right, green-clad McCoys. Each creeps towards a battle in the middle – and takeover of my garden.

What is an invasive plant?

It’s any plant with a will for world domination. Often, they’re not fussy and can grow almost anywhere (sun, shade; moist, dry; fertile, lean). That very fact makes the ornamental kind useful for dry shade like mine, but also makes them a potential pest. They reproduce easily – by seed or root or both. Once they do, they grow like, well, weeds, heartily and with few enemies, except perhaps each other. Take heed.

And welcome to the Toronto Gardens blog’s Garden of Regrets, Microgarden edition: Five plants I wish I’d never planted, plus a bonus two, all worthy of warning. Let me save you from my errors – and I hope you’ll share your own.

Tawny Daylily

When I wrote about the common ditch lily (Hemerocallis fulva) back in 2009, I was on the fence. Aggressive plants can be a boon in a dry-shade garden. But since then, after much (too much) weeding, that boon has become booooo!

Bright and cheery as this daylily is, I should never, ever have planted it. It’s a spreader in constant need of control. In shade like mine, it makes few flowers and, after they fade, the foliage does nothing but lie there and look exhausted. Blah.

The picture (above, right) of the sunny hellstrip between two neighbours down the street shows them at their best. Trapped by stone edging, they can flower their heads off, but don’t do your head in with their wandering ways. Daylilies that stay in a well-behaved bunch are much better choices. Be warned.

Periwinkle

The picture (below) might look attractive, but don’t be fooled. Planting periwinkle (Vinca minor), with its sinewy stems that clamber over everything and root wherever they touch, was a big mistake. Any plant that aggressively out-competes the plants you want to grow is an unwelcome space invader.

This is the “Hatfield” I mentioned before (V. ‘Atropurpurea’). Seduced by its large purple flowers, I planted just three 4″ pots ten years ago. Today, they cover a quarter of my garden. I mean cover. Great in the right situation. But not this situation. At right, I tried to de-vinca-fy. Two years later, the bits of root left in the soil still send up shoots. Shoot!

Don’t be like me. Don’t mix periwinkle with other low-growing perennials. And, for nature’s sake, never plant it (or other invasives) close to ravines or natural areas.

Sweet Woodruff

I used to like sweet woodruff (Galium odoratum). As long as my sandy, dry-shade garden was both dry and relatively infertile, this pretty groundcover remained in check. But. The minute I started feeding my soil regularly, it took off. It’s now the “McCoy” in my story.

The worst aspect, for me, is its tendency to like best the areas right on top of the crowns of plants I like better. See the bare spots above? See how sweet woodruff clings to the plants, rather than filling those bare spots? Tsk.

Each spring, I have to tweeze out Galium, carefully, without hurting the young shoots of the Brunnera (left) and Epimedium (right). (While you’re looking, note the runaway Hemerocallis.) Tweezing does not make for low-maintenance gardening. Beware.

Lily of the Valley

My love/hate relationship with lily of the valley (Convallaria majalis) of long duration.  Today, my position is: It’s fine in the right spot. My garden is not that spot. That spot is the stone-lined, straight-jacketed bed where the daylilies grow. Let them slug it out.

Continual weeding makes me continually wish I’d never planted those first few pips.

This is what happened when a neighbour transplanted a handful of pips from her grandparents’ garden. She moved on, but the plants are here to stay, colonizing the entire front yard. Yes, they’re adorable and fragrant in May; by fall, the flowers are forgotten, and wall-to-wall leaves are tattered and brown. So much for curb appeal. No.

Herb-Robert

Being a sucker for plant names, and married to Mr “Robert” TG, I couldn’t resist herb-Robert (Geranium robertianum). I sprinkled just a few seeds. Ha. More fool, me.

This little annual cranesbill has been in North America so long that no one is certain whether the vigorous self-seeder is native or naturalized. As always, Paghat’s Garden has something interesting to say about the plant’s history and lore.

See how innocent it appears (below) as a clump of filigree foliage and wee purple flowers? A closer look reveals it muscling in on a pink-flowered Heuchera ‘Sweet Tart’. Where, you ask? There on the right, drowning in delicate-looking, lacy leaves.

A foot or so over, the shot (left) shows it wrestling for dominance with Heuchera ‘Green Spice’ then (right) barging around, through, and behind a Hosta ‘Halcyon’.

A cool thing about cranesbills is how the ripe seeds sproing themselves around the garden. It’s the annoying thing, too. Weeding is not my favourite garden chore. So, add herb-Robert to my Garden of Regrets list – the list I hope you’ll never have to make.

Mint

Community and guerrilla gardens, like ours below, often get cast-off plants that become the gifts that keep on giving and giving and giving and giving. Mint (Mentha spp.) is one. It can start with the merest sprig. And it will grow. And grow. And grow. See the three zoom-out shots below. That edge-to-edge hedge at the right is mint.

Not only does mint spread by underground runners (sprouting roots called rhizomes), but every fragment of those roots can start a new plant. Sad example: Sarah once had an allotment where the entire site was roto-tilled at the end of the season. Someone was growing mint. By season two, everyone was growing mint. In abundance.

If you plant mint, do it in something like an old bucket with the bottom removed, sunk into the ground with the top edge above the soil level. That should slow it down.

Morning Glory

To show how determined invasive plants can be, consider morning glories. These hardy annuals have shared my back garden for 30 years. Thirty years of relentless self-seeding.

I believe they’re the heirloom Ipomoea purpurea ‘Grandpa Ott’, about which a reviewer on the Baker Creek rare seed site says: “…be warned, they will take over the world if you give them the chance.Yeppers. In my garden, they not only climb trellises and other plants, but think they have a right to claim the furniture, too.

What plants are in your own Garden of Regret? Please share in the comments. Let’s save the garden world, one invader at a time.

8 comments

  1. Oh, mint, and its cousins. Must go in containers. And thanks for the warning about Grandpa Ott – I have seeds but now I’m thinking I won’t plant them, at least not just anywhere.

    My “ditch” lilies must not be that species, as they are well-behaved. But I have a lot of plants that were once nice and tidy and now have gone wild: yucca, dwarf fountain grass, northern sea oats. I regret trumpet vine, too.

    Then there is the stuff I did not plant, like white mulberry (just learned that it is not the same as red mulberry) and the stuff that I think came in with free compost from the city. I get pretty discouraged sometimes fighting off invasives. Too bad the woodchucks and rabbits don’t eat them.

    1. Not everyone has the same bad or good luck, depending on your perspective, with ‘Grandpa Ott’ as I’ve had. My garden seems to be perfect for them. And I wouldn’t complain, but they really do weigh down the other plants. Do try them in a safe spot, because they are very pretty. The trick is not to let the seed ripen and spread.

      White mulberry (Morus alba) seedlings are always popping up in my garden. Good thing they’re easy to spot. And I never take city compost, for just the reason you state. In Toronto, dog-strangling vine is a big problem.

  2. Some of your dastardly plants do so poorly in my garden, guess climate zone really plays a big role in the allowance of those thugs to take over. My Sweet Woodruff just barely hangs on. The deer eat all my ditch lilies, I applaud the lily of the valley if it blooms…and on and on. Good to know we all can be smitten by a large purple bloom. Oh, and I sang a joyful song when my Physostegia was obliterated by brackish flood waters.

    1. Yeah, Janet, you’re quite right. “Invasive” really does depend on location. There are many things here in USDA Z5/Canadian Z6 Toronto that are quite safe to plant but that would be a nightmare in a South Carolina garden like yours. However, Physostegia or obedient plant is one that even we can have a problem with.

  3. I have a large part of my yard in south Etobicoke that is dry SILT. So as Janet from Seaforth, I am still waiting for some of these plants to go crazy. My periwinkle is contained by side walks, but there is a goldenrod that has required pulling up after just a few years. I would love to have woodruff, so MAYBE I will give it a go in the infertile sand. Thanks for this!

    1. Although wonderful for pollinators, Canada goldenrod (Solidago) is a notorious spreader. Unfortunately, the wild kind is often hard to tell apart from some of the better-behaved cultivars. Sarah grows a dwarf variety that is always being threatened by self-sown wild goldenrod. As I said above, sweet woodruff was a good friend in the garden until I started upping the soil fertility. Let us know how you get on with it.

  4. I’ve played with some of the same invaders you have in your garden. We inherited a slope of periwinkle and daylilies with this garden. Herb-Robert gets pulled a lot here as well. The others have been pretty easy to control. A love/hate relationship exists between me and the giant timber bamboo (a runner) planted 20 years ago before I knew anything about barriers. The digging of runners has become a summer long chore.

    1. Over on your side of the continent, mild winter weather is generally (now being an exception) a friend to invaders. One benefit of having harsher winters is a modicum of added control. That giant timber bamboo sounds scary, Peter. Is it like Japanese knotweed on steroids?

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