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13 perennials that are bad weeds

The novice gardener naively goes to the garden center to buy perennials for your new flower bed. You can trust that the merchant has made an interesting shortlist, right?

Not necessarily! Among the many well-behaving perennials on offer, there are also invasive plants (dangerously invasive) that will spoil your gardening pleasure for a long time. They are worse than most weeds, as they travel the entire bed (and even beyond the bed edges), choking out desirable plants in the process. I call them “fake friends” … and there are more than you think!

A false friend It is a plant that is offered as an ornamental but that behaves like a bully. Not only is it invasive, it is nearly impossible to remove. Try as you may, it will always grow back. A real poisonous gift!

[divider style=”dashed” top=”20″ bottom=”5″]These are the Invasive Plants you should stay away from[divider style=”dashed” top=”5″ bottom=”20″]

Here are some of the so-called “perennial ornamentals” that are actually invasive plants, weeds of the worst kind.

If you insist on planting them, make sure it is in a place where their ability to spread in all directions is not a problem, such as inside a solid barrier stuck in the ground, or better, in a container.

1 – 🌿 Louisiana Artemisia or scam (Artemisia ludoviciana) and
Steller’s Artemisia, canuta or polverosa
(A. stelleriana)

Louisiana Artemis or Estafiate (Artemisia ludoviciana) Photo: Amazon.com

Louisiana Artemis or Estafiate (Artemisia ludoviciana)

They are perennial plants with very silver leaves without noticeable flowering, with predatory rhizomes that quickly classify it as an invasive plant.

In contrast, other mugworts, such as the silver mound mugwort or Silvermound (A. schmidtiana ‘Nana’), perform flawlessly.


2 – 🌿 Small cypress or Esula minor
(Euphorbia cyparissias)

Euphorbia cyparissias.

Euphorbia cyparissias.

It is a small spreading plant that produces a mass of thin, gray-green leaves and fairly dense clusters of cream-colored yellow flowers.

Also, its milky sap it’s toxic and causes skin irritation.


3 – 🌿 Coin Grass
(Lysimachia nummularia)

Coin Grass (Lysimachia nummularia): here, the popular cultivar 'Aurea'.

Coin Grass (Lysimachia nummularia): here, the popular cultivar ‘Aurea’.

A very low groundcover with nearly round leaves, this yellow flowered plant will quickly sneak into any plantation.

This plant is not particularly harmful to the plants around it, but if you like to keep control of your plantations, it is not a good choice.


4 – 🌿 Angelica Minor or Herb of San Gerardo
(Aegopodium podagraria ‘Variegatum’)

Angelica Minor or St. Gerard's Wort (Aegopodium podagraria 'Variegatum')

Angelica Minor or St. Gerard’s Wort (Aegopodium podagraria ‘Variegatum’)

A ubiquitous perennial in our gardens and impossible to eradicate.

It is recognized by its highly trimmed white variegated foliage and white umbellate flowers. A plague!


5 – 🌿 Dotted loosestrife
(Lysimachia punctata):

Dotted loosestrife (Lysimachia punctata).

Dotted loosestrife (Lysimachia punctata).

Erect stems with yellow flowers. A pretty perennial, but too enterprising.


6 – 🌿 Macleaya
(Macleaya microcarpa and M. cordata)

Macleaya (Macleaya microcarpa).

Macleaya (Macleaya microcarpa).

Large perennial plant with curiously toothed leaves, very silver on the underside, feathery flowers. It stands out on our list of invasive plants since it is violently aggressive in sandy soils and, in addition, toxic.


7 – 🌿 Mint
(Mentha spp.)

Spike Mint (Mentha spicata)

Spike Mint (Mentha spicata)

Delicious perhaps, but mints (and there are dozens of species) are very invasive, even more so in humid soils. Every time I talk about them, I suggest that they be planted in pots to contain them.


8 – 🌿 Lily of the valley
(Convallaria majalis)

Lily of the valley (Convallaria majalis).

Lily of the valley (Convallaria majalis).

With its little scented bells, one is very tempted to plant lily of the valley, but will probably bitterly regret your purchase, the Top 2 on our invasive plant list.

What’s more, its red fruits are extremely poisonous; a real danger to young children.


9 – 🌿 Giant butterbur
(Petasites japonicus giganteus)

Giant butterbur (Petasites japonicus giganteus).

Giant butterbur (Petasites japonicus giganteus).

Sometimes called a “tractor seat” for the shape of its gigantic leaves or bog rhubarb, this plant quickly invades moist soil and cuts off all light to other plants.


10 – 🌿 Chameleon plant
(Houttuynia cordata ‘Chameleon’)

Chameleon plant (Houttuynia cordata 'Chameleon')

Chameleon plant (Houttuynia cordata ‘Chameleon’)

Nice tricolor foliage… but it will eat up your entire garden if the soil is even slightly damp.


eleven – 🌿 Japanese knotty grass
(Fallopia japonica):

Japanese knotty grass (Fallopia japonica)

Japanese knotty grass (Fallopia japonica)

The worst of false friends, this one ranks at the top of our invasive plants on this list. The thick rhizomes of this large perennial can cut through concrete and asphalt.


12 – 🌿 Grass Ribbon or Shepherdess Ribbon
(Phalaris arundinacea picta)

Tape grass or Shepherdess tape (Phalaris arundinacea picta

Tape grass or Shepherdess tape (Phalaris arundinacea picta

An herb with striated foliage that seems to want to conquer the entire world.


13 – 🌿 Cat’s claw or Pampajarito
(Sedum acre)

Cat's claw or Pampajarito (Sedum acre)

Cat’s claw or Pampajarito (Sedum acre)

A versatile little succulent… really everywhere! Unlike the other plants that appear here, the prickly cat’s claw or Sedum spreads mainly by seeds and not by rhizomes, mainly invading nearby lawns.


Do you have these types of plants on your property and you want to know how to get rid of them? The only realistic solution is … move! 🤭 No, I’m kidding… Read the answer to the next question.

[divider style=”dashed” top=”20″ bottom=”5″]How to get rid of lily of the valley or other invasive plants?[divider style=”dashed” top=”5″ bottom=”20″]

The lily of the valley invasive plant

Lily of the valley is pretty and fragrant, yet so invasive!

[box type=”shadow” align=”” class=”” width=””]Question: How can I get rid of lily of the valley on my property? AP[/box]

Answer: No matter how much you pluck the lily of the valley or dig the soil trying to remove it, you still leave segments of the rhizome in the soil and it can regrow even a small piece of rhizome.

Not even herbicides have been shown to be effective against this plant. The only logical way to kill him is take away the food.

This is because, like all green plants, the lily of the valley is totally dependent on the sun for its survival. Without light, it would die.

20210416p hoss tools

It is advisable to cover the infested area with a black plastic sheet.

The cloth should extend beyond the affected area (otherwise the plant will quickly send rhizomes in search of light). Secure it in place with rocks or stakes.

After 5 or 6 months, remove the fabric. If there are still white shoots, put the cover back on until the end of the following season (yes, lily of the valley, along with some other invaders, like Japanese Knotty Grass, is so hardy that it can sometimes survive more than one year without light).

Obviously, a black cloth is not very pretty. You can hide it under mulch and cheer it up with some potted plants.

The other possibility is reaping the lily of the valley. Cut it down to the ground. It will grow back. When you see that it grows back, reap again. And then two or three more times if necessary.

By cutting the green part of the plant, through which it photosynthesizes, you are depriving it of the solar energy necessary for its survival and, once it has exhausted the last reserves stored in its roots, it will eventually disappear.

Invasive Plants – The easiest way to control them is to avoid planting them!

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