15 Invasive Perennials That Can Take Over Your Garden

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I love perennials because you plant them once, and that space in the garden is taken care of for years to come. Sometimes though, certain perennials that seemed like a good idea at the time turn into a pain in the back after becoming invasive and taking over your garden.

Some of my favorite perennials have become invasive and spread far more than I anticipated, so they’re becoming more of a pest than a nice addition to my garden.

If you want to know which ornamental perennials to think about before planting them, here we go.

Contents

What are perennials?

Let’s first define a perennial plant. A perennial is a plant that lives, spreads and continues to grow for more than two years after planting.

While annuals are naturally limited by the fact that they die off each year, perennials prone to becoming weedy or overgrown have plenty of time to work their way underground or sneak into other parts of the garden.

Perennials are handy in the garden as they save time and are somewhat of a permanent fixture, while annuals provide quick but temporary cover and fill the space.

Perennials that invade your garden

This list does not encourage you to avoid these plants. You just need to be aware that they spread, often quickly, and many are difficult to eradicate. Consider where you will plant them and what surrounds them before you commit.

And remember: containers are your friends.

1. Nasturtium

Nasturtium (Tropaeolum spp.) is often considered an annual that reseeds easily, but in warmer regions (USDA growing zones 9-11) it is an endless perennial that spreads and takes over entire gardens and landscapes.

Once you plant it, nasturtiums constantly drop seeds and grow new plants among the older ones. It spreads easily and quickly.

Plant nasturtiums in containers to contain them and don’t let them spread too far.

I have a very large bank covered in nasturtiums and have given up on getting rid of them completely. I only control it when necessary by pruning it to limit its range.

2. Bear Panties

These herbaceous plants will form thick clumps that are almost impossible to fully dig up. Although you give it three or four feet to grow initially, it will soon expand outside and take over areas used by other plants. It will also shade small plants.

Some regions list bear breeches (Acanthus mollis) as an invasive species.

The plant itself has large, glossy green leaves with large, elegant flowers that grow upwards, but you have to wonder if that’s enough to negate the invasive habit.

3. Agapanthus

Often planted as an edging plant or space filler, agapanthus (African agapanthus) will form deep clumps. It sows easily and is difficult to dig out once established.

The rhizome roots quickly spread underground, and once that happens, the plant pops up unabated. It will cover an area of ​​the garden in a few seasons.

There are a few hybrid agapanthus that are suitable for growing in containers or indoors if you just must have this plant in your life.

4. Lamium

Lamium (Lamium maculatum) is an effective ground cover. It forms a thick carpet of foliage that even some weeds cannot penetrate. All is well until about five years into its growth, and you may find that it has crept into other areas quite a bit. Keep an eye on it.

5. Mint

Of all the perennials on this list, mint (Mint spp.) is well known for its invasive potential. This small area you planted in your vegetable garden for mint tea and mint sauce will spread to several areas of the garden.

Mint spreads underground and will appear in cracks in concrete, in garden beds and through gaps in patios.

It is best to plant mint in pots, buried in the garden or placed on it. If you plant mint in a submerged pot, make sure it is not cracked. Mint spreads so easily that it will escape through a crack.

6. Japanese Anemone

Don’t be fooled by the delicate appearance of this above-ground plant. Below it spreads quickly and is difficult to control once it starts to spread.

They have fibrous roots that are difficult to dig up completely. It is best to plant Japanese anemones (Anemone hupehensis) where they can spread or in containers to control them.

7. Wisteria

Glycine (wisteria spp.) is a woody vine native to China. It conjures up images of cottage gardens or lush English country mansions. It is also an aggressive perennial that spreads and clings to everything. Wisteria can damage your home or any other structure it grows on.

If wisteria wraps around a tree, it will eventually kill it.

Wisteria can become so heavy that it will topple a trellis that is old or has a weak spot. It is considered invasive in some states, but is also available for purchase in many places.

8. Tansy

Tansy (Tanacetum vulgare) is often used as a companion plant due to its ability to repel pests with its fragrance. It is a herbaceous perennial known to attract bees to the garden.

Tansy will spread by getting bigger, encroaching on other plants, paths and lawns.

9. Obedient Plant

It’s the only plant I know of where you can bend the stems to face any direction you want. This novelty is why many gardeners try it. This clump-forming perennial will spread very quickly through underground rhizomes.

It will spread and invade nearby plants, get under fences and into other nearby areas.

If you want to try an obedient plant (Physostegia virginiana), buy the ‘Miss Manners’ cultivar as it will stay in a tight clump and stay in its own zone.

10. Lamb’s Ear

Used by many gardeners as it is a slow growing perennial, Lamb’s Ear (Byzantine Stachys) not only spreads to lawns and other parts of the garden, it also starts to look a little tired after a few seasons.

Although it has been one of the prettiest perennials for some time, its invasive characteristics mean there are better options.

11. Bishop’s Weed / Snow on the Mountain

The variegated leaves of bishop’s weed (Podagrarian Aegopodium) make it an attractive ground cover. It doesn’t take long before these leaves cover just about everything in their path.

It’s also hard to eradicate if you decide you don’t want it anymore or if you’re tired of trying to control it.

Bishop’s weed spreads by underground rhizomes, so if you leave some in the ground, it will grow back quickly. It will take you several seasons to get out of your garden.

12. Ostrich Fern

ostrich ferns (Matteuccia struthiopteris) are hardy perennials in many places, but they are also invasive. Although beautiful, ostrich ferns will take over your garden. Plant them in a cool or moist woodland area where other plants are struggling.

In the garden, ostrich ferns will invade the area by spreading through underground rhizomes.

13. Creeping Bellflower

This hardy perennial is considered a noxious and invasive weed in many areas, but is often found in flower and perennial gardens. It spreads easily and is difficult to eradicate.

Creeping Bellflower (Campanula elegans) has a long taproot that breaks off the moment you try to pull the plant out. It will then sit quietly underground before working its way to the surface and rapidly spreading again.

If someone offers you a free creeping bellflower, politely decline.

14. Borage

For some, borage (Borago officinalis) is an annual, but in warmer regions it is a short-lived perennial. Although it spreads a bit where you plant it, borage pops up everywhere.

Borage is easily uprooted when seedlings are young, but as the plant ages it tends to break when pulled.

If you want hassle-free gardening and don’t want to chase your tail ripping up prolifically spreading plants, borage is something to leave out of your planting plan.

15. Comfrey

Comfrey (Symphytum officinale) will throw you into a false sense of security as it develops reasonably slowly to begin with. It dies during the winter and grows back twice as big the following year. Because it is low maintenance, it quickly spreads underground and pops up, taking you by surprise,

Comfrey is such a prolific grower that if you don’t dispose of it properly and throw the plants on a bank like I did, it will give you a whole new patch of comfrey.

If you want comfrey, but don’t want a spread, plant it in a container.

5 tips for planting perennials

  1. Take note of the size the perennial will reach and the likelihood of it spreading and reproducing.
  2. Consider your growing area and environment. A plant that is invasive in one area may not be in another.
  3. Plant perennials distributed by rhizomes in an area of ​​the garden that allows for supplemental plants.
  4. If you want to remove a perennial plant that spreads by rhizomes, it may take two or three seasons to accomplish this.
  5. If you have limited space or don’t want the perennial to spread, plant in containers and make sure the roots don’t poke through the bottom.

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