I am always looking for ways to gain the maximum benefit from the plants I grow.
When I think about what species to welcome into my precious garden space, one question I like to ask myself is, “Does this plant serve more than one function?”
For this reason, one of my all time favorite herbs to keep in my garden is comfrey!
This herbaceous perennial has an amazing variety of uses, from improving soil health, to attracting pollinators, and even fertilizing other plants. It is also a long utilized herbal support for wound healing and treating other ailments.
And it is extremely easy to grow – perhaps too easy, as it tends to spread if it’s not well managed.
But don’t let that scare you. Incorporating this remarkable plant into your landscape is absolutely worth it.
Read on to learn why I think it’s so special, and learn how to grow, harvest, and use this incredible plant.
What You’ll Learn
What Is Comfrey?
Cultivation and History
Propagation
How to Grow
Growing Tips
Maintenance
Species to Select
Managing Pests and Disease
Harvesting
Preserving
Quick Reference Growing Guide
What Is Comfrey?
Comfrey is an herbaceous perennial member of the borage family. While there are over 30 known species, only a few are generally cultivated for human use.
S. officinale is a common variety that is often used medicinally. It is native to Europe, as is S. asperrimum, or “rough” comfrey, which is named for its hairy leaves.
The plant most commonly grown in American gardens is S. x uplandicum, also known as Russian comfrey. It is a naturally occurring sterile hybrid of S. officinale and S. asperrimum.
This popular variety is easier to manage than S. officinale since it does not proliferate by seed.
This medicinal herb is easy to identify, with its clumps of large, upright, 12 to 18-inch hairy green leaves, and characteristic drooping clusters of bell-shaped purple flowers.
The ovate leaves grow rapidly and, if repeatedly cut down, comfrey can continue to flower all through the summer. You will often find it growing wild in disturbed areas.
Comfrey has a long history of medicinal use, and it offers a number of benefits for the garden.
Cultivation and History
Comfrey has been cultivated for medicine since around 400 BC. It was used by the Greeks and Romans to heal broken bones and wounds.
The word “comfrey” comes from the Latin verb confervere, and the botanical name Symphytum is derived from the Greek symphyo, with both meaning “grow together.”
A powerful healer, it is still used by herbalists today to treat wounds, bone injuries, and other ailments.
Native to Europe and Asia, wild comfrey was likely brought to the US by English immigrants for medicinal use.
In the 1800s, the S. x upandicum hybrid was heavily promoted by researcher Henry Doubleday as a food and forage crop.
However, recent studies have found it to be carcinogenic when taken internally in large quantities, potentially causing significant liver damage.
In the 1950s, Lawrence D. Hills, British horticulturist, founded the Henry Doubleday Research Organization in Essex, UK, to continue researching comfrey, and he developed a sterile strain known as ‘Bocking 14’ or Quaker comfrey, an homage to Doubleday’s religion.
Though no longer commonly consumed as food since we’re now aware of the potential health risks, comfrey still has so much to offer. Whether you are looking to build the soil, fertilize your garden, attract pollinators, or treat external injuries, this versatile plant is an incredibly worthwhile one to have around!
Garden Use
Comfrey is a rich source of nitrogen, phosphorus, and potassium as well as micronutrients including calcium and magnesium.
It is known in permaculture circles as a dynamic accumulator or nutrient accumulator; its long, thick taproots reach deep into the soil and draw potassium, calcium, and magnesium up into the above-ground parts, where they accumulate in the foliage.
It is worth noting that there is some controversy around this definition of comfrey as a nutrient accumulator and while there is an abundance of anecdotal data, it has not been scientifically proven.
The leaves can be harvested easily and used as a fertilizer or green manure to improve the nutrient quality of soil, and to support the growth of other plants.
In my experience, comfrey has been incredibly useful in building soil and supporting other plants, but in the absence of concrete data, you will have to draw your own conclusions!
Other potential benefits aside, the deep taproots are useful for breaking up hard, heavy clay soils.
And the rapidly growing, large leaves create a substantial amount of biomass, which can be cut repeatedly throughout the season and used to add a nutrient-rich mulch to annual garden beds.
I often apply the freshly cut leaves as a mulch directly on top of the soil, but for a neater look, they can be chopped up and worked into the top few inches instead.
This green manure can also be planted in a ring around perennial fruit, nut, or ornamental trees.
Cut leaves applied as mulch provide a much-needed source of potassium, an important plant nutrient.
Repeatedly chopping down leaves for mulch also causes some root dieback, which allows portions of the roots to decompose underground and recycle nitrogen, phosphorus, and potassium back into the soil.
Don’t worry about this dieback damaging your plants. This herb is vigorous, and in my experience, it will likely continue to thrive no matter what you do to it!
Leaves can also be incorporated into compost piles to accelerate the process. The high level of nitrogen available in the leaves can balance out a high carbon to nitrogen ratio, and helps jump-start the decomposition process.
Another way to take advantage of the nutrients available in this plant is to make a “comfrey tea,” which can be used as an organic fertilizer that’s rich in nitrogen, phosphorus, and potassium.
For complete instructions on how to make comfrey fertilizer tea at home check out our guide.
Research on the use of comfrey tea has also revealed that it can be used to prevent the spread of powdery mildew.
If these benefits are not enough to convince you of its usefulness in the garden, then you can simply delight in the fact that the beautiful bell-shaped purple flowers will attract plenty of bees, butterflies, and hummingbirds.
Medicinal Use
Soothing, slimy, and healing, comfrey is known informally as knitbone thanks to its long-standing reputation for being able to speed up recovery from bone injuries and wounds.
It has been used both topically and internally for many centuries in Europe to help heal broken bones, bruises, burns, and wounds.
Medical Herbalism: The Science Principles and Practices of Herbal Medicine
According to David Hoffman in his book “Medical Herbalism: The Science Principles and Practices of Herbal Medicine,” available on Amazon, the plant contains a chemical called allantoin, which encourages cell proliferation, meaning it helps cells to grow and repair more quickly.
Salves made from comfrey may help speed healing of broken bones, bruises, tendon damage, and torn cartilage, and can also help to reduce scarring.
A poultice of mashed leaves may also be used to heal cuts and scrapes.
The plant also has a history of internal use, specifically for treating ulcers and GI issues, but recent research suggests that it may not be safe for internal consumption.
It contains pyrrolizidine alkaloids (PAs), which have a rare but serious risk of accumulating and causing severe liver damage when ingested repeatedly over a long period.
There is quite a lot of conflicting information on whether or not comfrey is ever safe to use internally, even among clinical herbalists.
A Note of Caution:
Always seek medical advice from your doctor or other healthcare professional before taking any nutritional or herbal supplements. This information is not intended to diagnose, treat, or cure any condition and is for informational purposes only.
Propagation
Comfrey can be propagated easily from cuttings or by division. Popular species such as S. x uplandicum are sterile, and therefore can only be propagated by cuttings or division.
Cuttings are best transplanted during dormancy, in early spring or fall, though in my experience, mature plants are extremely hardy and can tolerate cuttings being taken at any time during the growing season.
I have dug up and transplanted giant plants in the middle of a sweltering summer and they still survived.
Leave ample space between cuttings when planting, as these plants grow and spread very quickly once they are established. About two to four feet between each should be enough space.
Once a patch has been established, you can divide plants or dig up pieces of roots to cut and replant.
One thing to keep in mind is that this herb can be difficult to remove from gardens. If even a tiny section of a root is left behind in the soil, it can sprout a new plant.
So be careful to plant only where you hope to have a long-standing patch!
Comfrey plants can be propagated by crown division or from root cuttings.
By Crown Division
Dig up half of a mature plant as instructed above. Holding the removed plant upright by the leaves, cut across the roots about three inches from the top.
This top section will be used for the crown divisions, while the lower roots can be used for root cuttings.
Remove the leaves from the crown, and break or cut the crown vertically into several sections about an inch or two in size.
Since each section contains tips and roots, these should sprout more quickly than root cuttings.
Replant crowns three to six inches deep in garden soil spaced 12 to 24 inches apart, with the roots facing down, and water thoroughly.
This is a faster method of propagation, and crown divisions typically take only 10 days to start producing new growth.
Comfrey crowns can also be purchased from your local nursery or online. But before you spend any money on bare roots or crowns, I would recommend checking in with your neighbors.
It is pretty easy to find a friend with extra comfrey to share!
From Root Cuttings
Choose a mature plant and loosen the soil around it. Split the plant down the middle with a spade, dig about a foot down to pull up half the plant, and refill the hole with soil.
The section left in the ground will recover quickly.
With the cut section, remove leaves and cut the long lateral roots to pieces two to six inches in length. Replant roots horizontally under two to six inches of garden soil.
Plant two inches deep in heavy clay soil, and closer to six inches in loose sandy soil. Water well
Continue to water every few days if conditions are dry. You will start to see new shoots poking out of the soil after about three to six weeks.
If you choose to grow crowns or root cuttings in containers for planting out later, choose a large pot at least six inches deep.
Plant three inches deep in potting soil and set in a cool room between 50 and 60°F that receives indirect sunlight. Water occasionally to keep moist but not waterlogged.
After about six weeks, once new leaves have begun to form you can transplant out to the garden.
From Seed
S. officinale, common comfrey, can be grown from seed. It is best to direct sow outdoors about three weeks before the average last frost date, planting about half an inch deep in soil.
Water well and keep the soil moist until seeds germinate in about two to three weeks.
How to Grow
There isn’t a whole lot to growing comfrey in terms of maintenance. It is an extremely tolerant and resilient plant.
Suitable for perennial cultivation in USDA Hardiness Zones 4-9, it is not very sensitive to soil conditions or pH, and it spreads rapidly.
There is no need to worry much about weed control, because comfrey’s large, quick-growing leaves will shade them out.
Even better, there is no real need to worry about pests and diseases, as this plant typically does not suffer from any major issues.
Its lovely bell shaped flowers attract pollinators and other beneficial insects such as parasitic wasps, which can help repel pests.
There are just a few simple tricks that I’d like to share, to help keep your comfrey patch at its peak:
Plant in full sun to partial shade. During the first year, harvest sparingly to allow plants to establish strong roots that penetrate deep into the subsoil.
After that, plants can be cut down several times a year.
If you are using comfrey for mulch, cut leaves as the flowering stalks begin to emerge, any time from late spring through autumn.
This can be done several times a year, as this herb continues to send up new flower stalks all season long.
Allow the plant to flower at least once during the growing season, to attract pollinators. I like to cut down different plants at different times so I will always have some flowers blooming in my garden.
It is important that these plants get adequate water, especially in dry climates. They can wilt quickly if conditions are too hot and dry, but generally revive quickly with regular watering.
Growing Tips
Plant in full sun to partial shade.
Harvest sparingly in the first year until root systems are well established.
Water whenever the top two inches of the soil are dry or when you notice wilting.
Maintenance
It doesn’t take much to keep comfrey happy. You can cut stems back after flowering to encourage repeat blooming.
However, keep in mind that this plant does have a tendency to spread. Avoid digging or tilling nearby; accidentally chopping up the roots can lead to inadvertent spread, making it virtually impossible to keep a patch under control.
If you want to remove plants from an area, you can try sheet mulching over them.
To do this, cut plants all the way down, place a thick sheet of cardboard on top of the soil, and cover with several layers of compost, straw, leaves, aged manure, or any other mulch material you have on hand.
You can plant a new garden immediately on top of the mulch, or allow the material to decompose for a few months first.
Species to Select
As mentioned, there are two main species, S. x uplandicum and S. officinalis.
If you don’t have a friend or neighbor with some cuttings to spare, you can easily source comfrey from your local nursery or online.
Also known as Russian comfrey, S. x uplandicum is a sterile hybrid that does not self seed. A vigorous grower, it is excellent for producing large amounts of biomass for mulch and compost.
This is the variety most commonly cultivated in US gardens.
‘Axminster Gold’
‘Axminster Gold’ is a variegated cultivar that has green and yellow foliage.
You can find S. x uplandicum ‘Axminster Gold’ plants in 2.5-quart containers available from Spring Hills Nursery via Home Depot.
Traditionally used for medicinal purposes, the leaves of S. officinale are more elongated than those of S. x uplandicum, and the flowers produce viable seed.
The flowers also tend to be cream or purplish in color, while S. x uplandicum has blue or violet flowers.
S. officinale
Packages of 10 seeds are available via Amazon.
Managing Pests and Disease
One great thing about comfrey is that it doesn’t typically have many problems with pests and disease, and those that do affect it don’t tend to be serious.
Just keep an occasional eye on your plants you shouldn’t have too much to worry about.
While this low maintenance plant isn’t bothered by much, there are still a few pests that can cause damage if you aren’t paying attention.
Slugs and snails can sometimes chew holes through foliage.
These slimy pests lay their eggs in moist soil and can multiply rapidly in cool, wet conditions.
If you have problems with snails and slugs in your garden, it is best to wait to mulch until dry summer weather or skip the mulch altogether.
You can remove these pests manually and drown them in soapy water, or sink small open cups of beer in the soil up to the rims to lure unsuspecting slugs.
Disease
While disease isn’t particularly common, comfrey can sometimes be impacted by fungal infections, especially in wet conditions.
Comfrey Rust
While rarely serious, this fungal disease caused by Melampsorella symphyti can weaken growth. It appears as small orange spots on foliage and can send out spores that can infect nearby plants.
With early detection, you can simply cut and dispose of infected leaves. If an infestation becomes serious, you may need to dig up and dispose of infected plants.
Do not use infected plants for cuttings as this fungus an overwinter in the roots. You can also plant Russian comfrey, which is typically resistant, in areas known to be plagued by this disease.
Powdery Mildew
Powdery mildew thrives in moist conditions and can sometimes cover comfrey leaves with a white powder-like coating.
You can treat mildew with a milk spray diluted with water at a 1:10 ratio. It is also a good idea to avoid overhead watering to prevent introducing excess moisture to your plants.
Read more about powdery mildew here.
Harvesting
You can harvest leaves sparingly the first year, but it’s best to wait until the second season when roots are well established to pick your first full harvest.
Once leaves are a couple of feet tall, cut them down by gathering a clump and shearing them off a few inches above the ground.
Plants will regrow to the same size within just a few weeks!
The leaves are a bit prickly, so you may want to wear gloves and long sleeves while you work.
If harvesting the roots, it is best to wait until late fall, which is when the plant is putting most of its energy into root development.
Seed saving is also possible if you are growing S. officinale, but it is a bit challenging since seeds ripen and drop from the plant on an ongoing basis throughout the season.
Covering seed pods with fabric seed bags will allow you to more easily collect seeds as they mature.
Store seeds in a paper bag or glass jar in a dark, cool location until you are ready to plant.
Preserving
You may use the leaves fresh for mulch or to make fertilizer, and dry the leaves and roots to make topical medicinal preparations such as infused oils or salves.
Comfrey fertilizer can be made by steeping fresh leaves in a bucket of water for several weeks.
The leaves are a bit challenging to dry because they are so fluffy and fleshy. For best results, lay them out in a single layer on a drying rack and flip them often, discarding any that show signs of mold.
You can also try drying them in a dark, dry room, or by placing leaves in a dehydrator or a warm oven. Once the leaves are completely dry, store them in an airtight container in a dark place.
To dry the roots, scrub them well and then chop them into small pieces prior to drying.
Once dried, they are nearly impossible to cut, so it is important to do this step while they are still fresh. The roots can be dried on a rack, in a dehydrator, or in a warm oven.
Make a Salve
Blend or mash up fresh comfrey leaves and infuse them in a carrier oil for several weeks in a sealed glass jar.
Cold-pressed olive oil is a great choice, but many types of neutral carrier oil will work. Place the jar in a warm and sunny location for the first few days, and then move it to a dark location like a cupboard. Shake daily.
After four to six weeks, strain out the herb and heat the oil in a double boiler with some beeswax, stirring frequently. Use one ounce of beeswax for every four ounces of oil.
Add a few drops of vitamin E oil to lengthen the salve’s shelf life. When the wax has melted, pour into tins or jars and set aside at room temperature to allow the mixture to set.
I love adding a few drops of mint or lavender essential oil into each jar for a bit of added fragrance.
Store the salve in a cool, dark location and use it topically on cuts, scrapes, bumps, and bruises to soothe external injuries and promote healing.
Quick Reference Growing Guide
Plant Type:
Perennial herb
Flower / Foliage Color:
Blue, purple/green
Native To:
Europe and Asia
Maintenance:
Low
Hardiness (USDA Zone):
4-9
Tolerance:
Poor to average soil
Bloom Time / Season:
Spring-fall
Soil Type:
Organically-rich
Exposure:
Full sun to part shade
Soil pH:
6.0-7.0
Growth Rate:
Fast
Soil Drainage:
Well-draining
Spacing:
2 feet
Companion Planting:
Fruit, nut, ornamental trees
Planting Depth:
2-6 inches (roots), 1/2 inch (seed)
Attracts:
Butterflies, hummingbirds, and other pollinators
Height:
3-4 feet
Uses:
Green manure, mulch, tea fertilizer, topical herbal remedy
Spread:
3-4 feet
Family:
Boraginaceae
Water Needs:
Moderate
Genus:
Symphytum
Pests & Diseases:
Slugs, snails; Comfrey rust, powdery mildew
Species:
Asperrimum, officinale, uplandicum
An Herb with Many Uses
It is hard to top a plant that can improve soil, support fruit trees, attract pollinators, add beauty, and provide medicine all at the same time.
Comfrey is a gardening must have, in my opinion. It offers so many benefits and, once established, it takes virtually no effort to keep it around.
How do you like to use comfrey? Share your tips in the comments section below!
And for more information about growing medicinal plants in your garden, have a look at these guides next:
How to Grow Pot Marigold (Calendula) Flowers
How to Grow and Care for Borage Plants
How to Grow Common Chicory
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