Comfrey is a common plant that many gardeners have to deal with. When the bluish-pink flowers started popping up in my garden, I didn’t give it much thought. But then, the plant started to overstay its welcome. That’s why I did some research to figure out how to get rid of these plants once and for all.
You can get rid of comfrey in your garden by using organic acids like acetic acid and citric acid. You can uproot or dig the plant out of the ground and use it in compost, mulch, or liquid fertilizer. Or you can use a chemical like Glyphosate to get rid of the comfrey plant.
These plants are wildly invasive and grow pretty much anywhere. They overcrowd gardens, leech food supplies from nearby plants, and leave behind fast-growing roots to sprout up new growth.
Comfrey is carcinogenic and can cause liver damage when ingested. So it’s harmful to both humans and pets. That’s why it’s best to get rid of them so let’s look into more details on how to do this.
How to Kill Off a Comfrey Plant
Due to its invasive nature, Comfrey can spread very easily throughout your garden. It’s also a pain to get rid of. The roots of the comfrey plant run very deep into the soil. Furthermore, the plants can regrow with just tiny root fragments as a base.
Removing the plant from your garden is no easy task, but it’s possible with some careful planning and vigilance. Here are some common methods gardeners use to get rid of the comfrey plant.
Uproot the plant from the ground
The root system of the comfrey plant can be as deep as two meters. The roots help to absorb nutrients in the subsoil, which is why the plant is so robust.
To uproot it, cut the top of the plant at the stem. Leave about six inches of the stem above the ground.
Now, use a high-leverage weed removal tool. Grasp onto the stem tightly using its jaws and pull the handle back to pull the roots up.
Comb through the soil as you pull the plant out to ensure that you’re not leaving anything behind.
Dig the plant out of the ground
Uprooting can be effective, but digging can ensure that you’re getting everything. The roots don’t just grow deep. They also grow laterally, leaving a network of growth about three feet side.
Cut off the top of the plant and start digging about three feet out from the main stem. Dig below the stem and create a wide perimeter around the plant.
The goal here is to work your way around the root system while loosening the soil. Once you’ve loosened all of the roots, you can pull the entire root mass out in one piece.
Use organic acid to kill the plant
If the comfrey is located near crops, you’ll want to avoid any chemical herbicides luckily, there are a few organic options you can try out.
The most effective organic ingredients to try out are acetic acid and citric acid. These are often used in organic commercial products. Alternatively, you can make the herbicide yourself.
Both acids work by destroying cell membranes. It works on contact and quickly makes the plant start wilting.
Pick up some acetic or citric acid solutions. Vinegar is a good source of acetic acid, but store-bought options usually have a concentration of about five percent. For better results, look for stronger vinegar products with up to 30 percent concentration.
Mix about 1 quart of the vinegar with about four ounces of lemon juice for citric acid. Then, spray the leaves, stems, and roots of the comfrey plant. Repeat applications as necessary until the plant dies off.
Use synthetic chemical to get rid of the plant
Chemical herbicides can be quite effective for killing off comfrey. The chemical you’ll want to use is glyphosate.
Glyphosate is a nonselective herbicide. This means that it will kill most plants effectively. While this does mean that it can take care of comfrey, it also means that you have to be extra careful not to spray it on surrounding plants.
This particular chemical works by inhibiting an enzyme called EPSP synthase. The enzyme is responsible for producing proteins the plant needs to grow. When you apply it to the leaves of the comfrey plant, it will travel through the tissue and accumulate in the roots.
Start by covering nearby plants with non-porous plastic. Then, fill up a pump sprayer with a gallon of water. Add the appropriate amount of glyphosate according to the instructions on the product label.
You can easily find glyphosate in commercial weed killers. For optimal results, I recommend getting a 41 percent concentrate. It’s far more effective than mixes that contain other chemicals.
Now, mix the solution thoroughly, build up pressure in your pump sprayer, and start applying the chemical. Spray the comfrey plant thoroughly. But, don’t spray it so much that the chemical starts running off.
Give the glyphosate about a week to work its magic. If the plant is still alive, apply some more chemical herbicide.
How Do You Use Comfrey in the Garden?
Once you have effectively removed the comfrey plant, don’t throw it away just yet!
While the plant is invasive and troublesome when it’s growing in the garden, you can take advantage of the plant elsewhere. Here are some ways to use comfrey to help your garden.
The roots, stems, and foliage are perfect for creating compost. You can toss it into your normal compost pile to make a nutrient-rich fertilizer for your garden.
The roots are particularly beneficial. Because they are so deep, the roots can absorb nutrients that other plants aren’t able to utilize. The subsoil is rich in nitrogen, sulfur, phosphorus, zinc, and potassium. It also has many trace elements.
Many gardeners use comfrey as a bioreactor to get the compost going. Cut the plant into small pieces and layer it between dry materials. Then, compost as normal.
When finished, the compost will have a much higher nutrient content than normal.
That discarded comfrey is also perfect for making liquid fertilizer. All those great nutrients from the subsoil don’t remain in the roots. They travel up to the foliage, too.
To make liquid fertilizer, collect the comfrey leaves and place them in a large container. Something like a five-gallon bucket works well. Using a rock or brick, crush the leaves as much as possible. Alternatively, you can use scissors to cut the leaves before adding them to the container.
Cover the container and let the leaves break down for as much as six weeks.
Eventually, the leaves will break down into a thick black liquid. This is your liquid fertilizer!
To use it, dilute the liquid. A ratio of one part liquid to ten parts water is ideal. Use the diluted liquid to side-dress your plants! The nutrients will encourage flowering and help your plants reach their full potential.
If you don’t want to go through the trouble of creating compost or liquid fertilizer, you can apply the leaves as mulch. The mulch will help retain moisture while also letting your plants take advantage of the comfrey’s rich nutrients.
Apply two to three layers of leaves around your plants. To speed up decomposition, you can cut the leaves in half or crush them up before applying the mulch.
How Do I Make Comfrey Tea for My Garden?
If you’re familiar with the concept of compost tea, you already know the benefits it has to offer. Teas are capable of enriching the soil in your garden while also making nutrients readily available to your plants.
The results of using garden teas speak for themselves.
Thanks to the nutrient-rich nature of comfrey plants, many gardeners use it to make teas.
Comfrey is considered a dynamic accumulator. In the world of permaculture, a dynamic accumulator is a plant that gathers nutrients from the soil and makes them in a more accessible form. Comfrey checks all of those boxes.
Because the roots penetrate so deep into the soil, the plant is able to access nutrients that would otherwise wash away. Most plants just aren’t capable of absorbing those nutrients. Instead, they focus on nutrients near the soil.
This can be an issue over time. To more plants you cultivate in a given area, the fewer nutrients the soil will have. Comfrey tea can work to reinvigorate the soil and make your garden more viable for years to come!
Brewing Comfrey Tea
The first step is to gather comfrey leaves. Remove all of the leaves from the plants you removed from your garden. Cut the leaves off of the stem so that you only have soft foliage to work with.
Now, gather a large bucket with a lid. The lid is crucial here! Brewing comfrey tea is a smelly process that will attract pests. The lid will keep the smell contained and keep flies out.
Fill half of the bucket with the comfrey leaves. For a stronger tea, you can fill it up about three-quarters of the way. Then, weight the leaves down with a heavy rock or a piece of wood.
Fill the bucket up with water and close the lid. Wait for about 20 days for the leaves to steep.
As the leaves decompose, they’ll fill the water with nutrients. The final result is a potent tea that you can use to support your garden.
Using Comfrey Tea
It’s best to dilute the mixture by at least 50 percent. You may want to dilute it even more if you’re side-dressing plants.
You can spray the tea directly to the foliage or focus on specific plants by applying it to the roots. The tea also works great for infusing the soil with nutrients. Just spray the soil, work it in, and repeat as necessary.
Here are some of my favorite container gardening tools
Thank you for reading this post. I hope it helps you with your gardening needs. I’ve listed some tools below that can help you with container gardening. These are affiliate links so I’ll earn a commission if you use them.
Gardening Gloves – I find the Pine Tree Tools Bamboo Gardening Gloves really good for both men and women. It’s made from bamboo so helps absorb perspiration. They are also comfortable and fit very well.
Containers – You know picking the right container is crucial for your container gardening. I’ve written a detailed post on the best containers you can choose from. If you’re happy with a plastic container, you can check out the Bloem Saturn Planter.
Watering Can – This is a must-have tool when you’re growing plants in pots or grow bags. It helps to water the potting soil without splashing on the foliage. The Kensington Watering Can is stylish, strong, and can provide precision when watering potted plants.
Trowel – Garden Guru Trowel is my favorite because it’s durable and comfortable to use. My gardening friends really love having a trowel because they use it for digging soil, mixing fertilizer, moving seeds, leveling out the soil, mixing compost or mulch, and also dividing tubers
Bypass Pruner – I really like the Corona Bypass Pruner because it’s durable and gives a clean cut that helps plants recover faster. If you’re looking for something cheap, get the Fiskars Bypass Pruner that is really good as well.
To see an extensive list of the best container gardening tools gardeners recommend, check out this resource that I made for you.
Kevin is the founder of Gardening Mentor, a website that aims to teach people to grow their own food in a limited space. As a self-taught gardener, Kevin has spent several years growing plants and creating gardening content on the website. He is certified in Home Horticulture and Organic Gardening by expert gardeners from Oregon State University.