Can Perennial Plants Spread and Become Invasive?


ferns in the garden

Perennials are good-looking and a low-maintenance investment option for gardeners. The life cycle, blooming time, culture, and form of each perennial plant varies significantly. However, there are quite a few perennials that can be super-efficient.

Perennials are usually more difficult to control than annuals or biennials because they spread both vegetatively and by dispersing seeds. While some are invasive, others take a lot of space. However, perennials considered invasive in one area may not necessarily be invasive in other areas.

Perennials may invade your flowerbeds and crawl their way into your lawn. Soon these easy-care and dependable performers can turn into a big hassle for a gardener. Here is some important information related to plants that spread and become invasive, along with a few examples:

What Makes Plants Invasive?

Invasive plants are not innately aggressive. Every plant possesses a set of traits that helps them compete against the various hurdles of nature to survive, thrive, and reproduce.

From the beginning of time, plants have constantly been developing and evolving to compete for resources while also surviving environmental pressure, weather events, pathogens, fungi, and diseases.

Now, there are times when a certain variant of a species that has succeeded in this battle is transported to a new region. This region may not necessarily have the familiar forces of competition and resource availability that the plant is used to. This is when a plant’s invasive properties can emerge.

Common Invasive Perennials

Here are some of the perennials that can spread and become invasive:

Ostrich Fern

Ostrich Fern is a perennial that grows up to resemble elongated feathery ostrich plumes. They can spread through underground runners. Various gardeners avoid growing it in their home gardens as it can easily take over. So, if you are planning to get Ostrich fern, it is better to drop the idea.

However, if you have a damp wooded area and cannot find anything to grow there, you may go with Ostrich fern but with caution.

Ostrich Fern can spread up to eight feet in width and grow around two to three feet tall. They tend to grow even taller, up to six feet tall, in moist or cool climates. So be sure that you grow it in an area that can be easily controlled and discourage its aggressive growth.

Lily of the Valley

white lily of the valley

The lily of the valley is a popular choice for bridal bouquets, majorly because of its delicate looks, sweet-smelling flowers resembling white tiny bells, and lush green leaves.

However, it might not be an ideal pick for a gardener. This is a perennial plant that grows from underground rhizomes. While they may seem to be delicate, they spread horizontally and usually at an alarming speed. They can tunnel and spread easily unless the quality of soil is poor.

Considerations of the Lily of the Valley

Although the blooms do not last long, the stalk-like leaves remain intact for the entire growing season.

This makes it a good option for a ground cover crop.

Also, it should be noted that the lily of the valley is always invasive. It can be well-referred as an aggressive plant which powerful rhizomes.

Creeping Bellflower

These are some of the most commonly known invasive plants. The blue and trumpet-shaped flowers of a creeping bellflower grow on a tall stem.

While they look quite pretty, planting them in your garden can turn out to be a huge mistake.

Creeping Bellflower growth and considerations

Creeping bellflower can spread through seeds and rhizomes that are 8 inches below the surface. But what makes it so invasive is the fact that it moves around under the flowerbeds, lawn, and almost everywhere in your garden.

Moreover, a creeping bellflower can self-pollinate and make seeds that further increases its chances of spreading.

It also does not have any specific requirements. It will not only grow but thrive in conditions like wet or dry soil, direct sunlight, or full shade. So, it is not surprising that limiting its growth can be quite tiresome for a gardener.

Tansy

tansy

Believed to ward off mosquitoes, tansy is a perennial flowering herb. It has a peculiar, spicy scent and was used for medicinal purposes back in the day. Once termed as a medicinal herb, tansy is referred to as a weed in the modern world. And while it may have attractive looks, one cannot overlook the fact that it can be an invasive plant.

Considerations when handling Tansy plants

Moreover, the oils in tansy are quite toxic, so while working, you should ensure that you wear gloves to avoid direct contact. This also means that a home garden frequented by pets or other animals should not house tansy, owing to its toxicity.

Now, coming to its invasiveness, tansy is self-seeding, which makes it a prolific reproducer.

And while it also grows from rhizomes, the process is quite slower than self-seeding. This is the reason why one may come across tansy-filled fields on the roadside. That is exactly where they belong rather than a home garden.

Ox-eye Daisies

Do not let the looks deceive you. Ox-eye can be mistaken for Shasta daisies quite easily and are quite eye-pleading. But they are, in fact, common wildflowers that grow on roadsides and fields. These are easy to grow, need little to no care, and can rapidly proliferate in your garden.

Ox-eye daisies are considered to be invasive in various regions. They can produce around 1,300 to 4,000 seeds in a year. And they also spread through creeping rhizomes or horizontal root stalks, making them a lot more aggressive.

If not controlled, these can result in soil erosion and may degrade natural resources as they can easily outcompete other native plant species.

Ribbon Grass

Anyone can fall in love with this variegated grass. But that is true only if you go just by the looks.  It does not have a good reputation when it comes to being obedient.

It can be used as a ground cover in tough spots or areas where nothing else may grow.

Still, it requires a lot of caution as it can spread quickly and choke out native plants. If one variety of a certain perennial is known to be invasive or aggressive does not imply that all the varieties are invasive. Also, a plant considered invasive in one region does not necessarily mean that it is also invasive in other areas of the country.

Tips to Avoid Perennials from Spreading

flowers in tea cups

If you are planning on getting perennials for your garden, here are a few tips that will help you avoid them from spreading:

Researching is important to avoid spreading perennials

The first and foremost step is to have proper knowledge about the kind of plants you wish to grow in your garden. It would help if you executed thorough research that will tell you about its blooming time, lifecycle, time, and way of reproduction.

Also, while buying plants, you need to look for terms like ‘wildflower,’ ‘weed,’ ‘invasive,’ ‘aggressive,’ or ‘vigorous spreader.’

Grow the Perennials in Pots to stop them from spreading

One of the easiest and quickest ways of discouraging plants from rapid spreading is to grow them in pots. By picking some decorative pots and planters, you will prevent aggressive spreading and add beauty to your garden.

While this would discourage growth from rhizomes, you would still need to take certain measures to control the growth from seeds.

Other than this, it would help if you were sure that you pick planters with holes to help in better water drainage.

Try Pruning to keep Perennials from spreading

pruning flowers

Pruning prevents the plants from forming flowers; it is an amazing way to prevent perennials from spreading. Moreover, it would help if you also were sure that you remove the heads of the wilted flowers as soon as possible to avoid reseeding.

While doing so, you need to be extremely careful that you do not disturb the soil.

This is because seeds can germinate well in loose soil. So, when you are done, take a moment to step down all loose soil. To aid you with this, I have written an article on pruning and how it may also be compared side by side to thinning. It covers just when to prune and when to consider thinning for plants, their benefits as well as considerations.

Forming Strong Barriers can stop Perennials from spreading

Plants either spread by sending out roots or dropping seeds, or both. Building strong barriers can at least control spreading plants through roots to a certain extent.

For instance, underground plastic corrals are known to discourage plants from spreading, and it will only work when it is at least 10 inches deep or even more.

One can create these corrals by cutting off the bottom part of a plastic pot and then bury the pot underground. Then, space needs to be filled up with soil while the plant is placed inside to grow.

Use Mulch to stop perennials from spreading

mulching perennial beds

While barriers can help in preventing spread through roots, mulch can help in preventing spread through seeds. To ensure this technique works, you should first mow and removing as much vegetation as possible.

Then, it would help if you watered the area to ensure it is well saturated. This step will help in removing air from the soil. One should apply a thick layer of mulch to prevent seeds from germinating or even to smother seedlings.

Mulching considerations

However, if there is a dense infestation, you need to smother it with a thick layer of newspapers or cardboard.

You can hold them into place with the help of heavy stones. To give this a better look, you can cover the cardboard with mulch.

This would deprive the plant of sunlight, overheat and starve it. Thus, the plant will eventually wither. During this process, you may also have to lose some native plants under the layers. To aid you too with this process, I have created a recent article on the best mulches to consider in the garden. It covers the different mulch types—the process of making some of them as well as their subtypes.

Do Curbing to stop perennials from spreading

If you come across a plant that has started spreading to a spot where it is not wanted, you must take immediate action to prevent it from further spreading.

For this, you need to dig the plant right from the roots. To avoid the plant from spreading to a certain spot, you can install high-quality concrete curbing/edging.

This would not only prevent spreading but would also give your garden a much beautiful, organized, and clean look.

Conclusion on perennial plants spreading and being invasive

While some live for around three to four years, some can live up to fifteen years, in the case of peonies, a lifetime. Once planted, they will return year after year without the hassle of replanting.

We hope that this information will help you get a better idea of invasive plants and how you can prevent them from spreading to a certain level. This would help you pick the right plants and build a healthy and good-looking garden. However, one should still be cautious of the above-mentioned perennials that are known for their notorious behavior.

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Tony O'Neill

I am Tony O'Neill, A full-time firefighter, and professional gardener. I have spent most of my life gardening. From the age of 7 until the present day at 46. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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