Growing your own herbs is a great way to get them fresh. Many herbs are easy to grow, even for first-time gardeners; however, those easy ones are usually quite invasive. But does that mean all herbs are invasive?
Not all herbs are naturally invasive; however, they can take over your garden if left alone. Some herbs are naturally invasive, propagating and taking over entire gardens with no help. Others will grow in their dedicated spaces if they’re properly cared for.
In the rest of this article, I’ll explain which herbs are the most invasive and how to control them and keep them from spreading. If you want to know more about these topics, keep reading!
Which Herbs Are Considered Invasive?
Most herbs reproduce pretty easily, which is why they’re so easy to raise. Even beginner gardeners don’t have to do much apart from planting them and ensuring that the soil type and weather are conducive to growing herbs.
You can learn more about this in my other article, How Cold is Too Cold for Outside Herbs. However, some herbs spread so easily that they can become a complete nightmare!
Herbs that propagate through rhizomes or runners are considered the most invasive. These herbs include mints (all types), pennyroyal, etc. Other invasive herbs include ones that produce a lot of seeds, like comfrey and lemon balm.
Herbs that propagate through rhizomes or runners are considered the most invasive. These herbs include mints (all types), pennyroyal, etc. Other invasive herbs include ones that produce a lot of seeds, like comfrey and lemon balm.
Herbs propagate in three ways: seeds, cuttings, and division. Most invasive herbs spread through their seeds or rhizomes.
Rhizomes are plant stems that grow underground instead of above. These stems run horizontally along the ground and occasionally produce shoots that break through the ground and grow above. Plants with rhizomes tend to propagate extremely quickly, which is why some rhizome plant species have been classified as invasive.
Some herbs, like comfrey and lemon balm, spread more through their seeds. These herbs are also considered invasive, even though their propagation method is different.
Here are a few herbs that are considered invasive.
Mints
Any herb from the mint family is considered invasive. These herbs spread like wildfire, taking over entire gardens relatively quickly. Herbs from the mint family that spread through rhizomes include spearmint and peppermint.
These are considered the most invasive species. Mint plants grow up to 2 feet (0.61 m) in 6 months, but they actually spread far more than that because of their rhizomes. These can cover several feet of land in a few months.
Mints are useful for a variety of reasons, but they’re most commonly used in cooking or as a garnish.
Comfrey
Comfrey spreads like wildfire because of its high seed production. It’s highly valuable for its medicinal use and can also be used as animal feed or fertilizer.
Comfrey flowers have to be regularly trimmed to keep them from spreading. If left alone, they produce seeds that can cover a large area, even sprouting in cracks in the pavement or random patches of land.
Lemon Balm
Although lemon balm also has runners like mints, these herbs spread mostly through seeds instead. Garden owners who grew lemon balm in their yards reported that the plant tends to grow back in bigger sizes each season.
While lemon balm doesn’t always cover a large area, it tends to grow to a bigger size, thereby occupying more space.
Artemisia
Artemisia, also known as Mugwort, is a perennial herb that has been widely used historically for its medicinal properties. Many traditional forms of medicine in different countries still use this herb to treat ailments.
Some subspecies of this herb are also excellent for managing soil erosion, ensuring ground cover, and producing beautiful foliage. This herb is known for producing a large number of seeds – one particular variety, the Artemisia absinthium, can produce up to 50,000 seeds from just one plant! As a result, just a single plant can produce enough seeds to take over your garden.
Catnip
All cat owners will be familiar with this particular herb! Catnip is often used to excite cats, who tend to become hyper and playful because of its smell. However, it’s also used in herbal teas to treat restlessness, nervousness, and a multitude of other ailments.
Catnip also spreads via seeds, so you’ll need to trim the flowers before they produce seeds if you want to keep it under control.
Fennel
Fennel is used widely for medicinal and culinary purposes. It’s packed with nutrition and widely used in herbal teas or cooking to provide essential nutrients.
Some studies suggest that fennel can improve heart health and fight cancers. It’s also widely used to treat inflammation and bacterial infections.
Fennel is one of the most invasive herbs, often considered a weed because of its high spread rate. It propagates via its seeds, so cutting the flowers before they produce seeds can keep it under control.
How Do I Stop Herbs From Spreading?
If you’ve got an infestation of herbs you don’t want, getting rid of them can be a task. Herbs spread uncontrollably, so pulling them out of the ground isn’t enough to control them completely.
The method of controlling them depends on how the herbs spread. Herbs that spread through producing copious amounts of seeds need a different containment method than herbs that propagate through rhizomes. So before you start, you should research the herb you’re trying to contain and find out how it reproduces.
Here are a few ways to control the herbs in your garden and stop them from spreading.
Prune Large Patches
Some herbs can be considered invasive even if they simply take over a larger patch of land than intended. If you find that one plant has grown so much it’s encroaching on another plant’s land – that qualifies as invasive.
These types of herbs are the easiest to control. You just need to regularly prune the outer branches of the plant to prevent it from becoming too large. This way, the plant remains within its designated boundaries.
Plant Herbs in Containers
As I mentioned earlier, some of the most invasive herbs spread through runners or rhizomes. Thus, you have to limit the spread of the runners to contain the herbs within their designated area.
A simple and effective way of doing this is to plant these herbs in containers. You can keep them in pots above the soil or put them into a container within the ground. Planting in a container inside the ground allows the roots to absorb nutrients from the soil in your garden. Keeping them in containers will prevent the rhizomes from spreading, containing your herbs in one place.
Deadhead Herbs with Seeds
Deadheading is a practice where you cut off fading or withered flowers from plants. It’s a form of pruning that maintains the plant without compromising its size. Deadheading has numerous benefits, but the main one we’re looking at here is its effectiveness in containing herbs.
One of the most common ways seeds spread is through flowers that dry up and fall to the ground or get carried away by the wind. Removing these fading flowers stops the seeds from reaching other parts of your garden.
If you notice any withered flowers or ones with their color fading, just cut off those flowers and collect them in a basket or container of some sort.
Put up a Weed Barrier
A weed barrier is a material or mulch that can be used to prevent weeds from growing in a particular area. They essentially form a barrier or containment line around the plants.
There are two ways of laying down a weed barrier.
- You can lay the fabric down and then cut slits into it where the plants will go.
- You can put the fabric over existing plants and cut slits to work the fabric down over the plants.
Regardless of the method used, you’re normally supposed to cover the weed barrier with mulch to prevent it from degrading.
Weed barriers are a great way of keeping your herbs organized and contained because they prevent the herbs from spreading into the area covered by the fabric. If you have a persistent problem with invasive herbs, you can use a weed barrier to keep them contained and organized.
Final Thoughts
While most herbs are considered invasive, the degree to which they spread differs. Some herbs, like mint, comfrey, and lemon balm, are known to be incredibly invasive, while others spread more slowly.
Generally, herbs can be contained, even if they’re considered an invasive species. The method used to contain them depends on how they spread. Using the right methods should ensure that you have a beautifully organized garden.
