Comfrey plant: soil improver and pollinator bait

As a mulch, fertilizer, compost accelerator, pollinator attractor and clay soil breaker, the comfrey plant is an invaluable asset to any garden.

The first comfrey shoots appear in spring. By June, it grew waist-deep with a host of pretty bell-shaped, pink to purple flowers, each with a tiny beehive sticking out of the end as they feast on the rich comfrey nectar.

I let the bees feast for a few weeks before I get my first harvest. The stems are cut to ground level and then roughly chopped and added to my cold, high carbon sleeping compost as a much needed nitrogen boost.

In a matter of weeks, new leaves germinate, 12-15 inches long, and are ready for harvest to feed the now-hungry vegetable and fruit crops. Comfrey leaves are rich in potassium and trace elements, magnesium and calcium, perfect for tomatoes, peppers and pumpkins.

And so the cycle begins for at least two more harvests. That is at least 3-4 harvests per season. What's not to love about comfrey?

Good products on Amazon for growing comfrey plant:

Brief instructions for care

The comfrey plant is a garden powerhouse that is worth growing. Source: London Permaculture

Common names Comfrey, knitbone, bruisewort, knitback, church bells, Russian
Scientific name Symphytum officinale, Symphytum x uplandicum
family Boraginaceae
Height & Spread 3-4 feet high, spread indefinitely
light Prefers moist soils, but is also drought tolerant
floor Loam, well-drained, retains moisture
water Water weekly
Pests & Diseases Slugs, snails, powdery mildew, comfrey rust

All about comfrey

Comfrey is a hardy herbaceous perennial and belongs to the borage family Boraginaceae, which includes borage, forget-me-not, Echium, Brunnera and Cerinthe. There are two main types of comfrey, Symphytum officinale, also known as common comfrey, which is native to Europe and Asia, and Russian comfrey, Symphytum x uplandicum, a naturally occurring hybrid that was first discovered in Upland, Sweden in the 19th century . S. x uplandicum is a cross between comfrey and Symphytum asperum, the blue-blooded rough or prickly comfrey originating in Russia.

Comfrey has been grown since ancient Greece and Rome when it was primarily used medicinally as a poultice to heal broken bones, bruises, and other injuries, hence the common names knitbone, knitback, and bruisewort.

Although the appearance and cultivation are similar, there are some important differences between common and Russian comfrey. Comfrey can reproduce by spreading seeds, making it potentially invasive. Russian comfrey flowers are sterile, so they are propagated by cuttings and division. Russian comfrey leaves are larger and produce higher yields.

The first green shoots of the comfrey grow as a basal growth from the crown of your garden bed in mid-spring. It quickly forms a large clump with leaves 30 to 35 cm in length, lanceolate, green and roughly structured with many small spiky hairs that can be irritating to the skin.

When late spring subsides and temperatures rise towards summer, thick branched flower stalks with smaller leaves emerge from the crown. Groups of pendulous tubular bell-shaped flowers appear, which vary in yellow, pink, purple and blue depending on the species. At full height, comfrey can reach 90-120 cm.

Comfrey dies naturally after flowering. The heavy stems often break down and are quickly replaced by new shoots. Cutting back the plant before flowering will speed up regrowth. Cold autumn temperatures initiate the winter dormancy.

The types of comfrey to look out for include:

  • Bock 14: An excellent variety due to its high potassium content, which can be used as a mulch or liquid fertilizer for fruit crops. This comfrey contains 7.09% potassium compared to 3.09% in other types of comfrey.
  • Hidcote blue: An attractive perennial that grows up to 50 cm high and 60 cm wide.
  • Axminster Gold: A variegated variety with long green leaves with yellow edges 46 cm high.

Purple comfreyComfrey flowers in a variety of colors, like this purple. Source: Unconventional Emma

Use of comfrey in permaculture

Comfrey is the star of any permaculture garden, especially the Bocking 14 strain. The only problem with growing comfrey is keeping up with your garden's harvest. Here are some ways to use comfrey as a multipurpose plant type in your garden spaces!

Mulch: Mulches help retain moisture and add volume and nutrients to the soil. Comfrey Mulch does all of this with a mega-boost of nitrogen and potassium. Just chop and drop!

Comfrey tea fertilizer: This is achieved by soaking the leaves in water for up to six weeks. They know it's done when the mixture gets slimy and smells like rotten eggs. Strain the liquid and dilute it 1:10. The longer the leaves pull, the stronger and darker the tea.

Comfrey concentrate fertilizer: This takes a little longer than comfrey tea, but can be kept for up to a year. The concentrated fertilizer is made by pressing the leaves together with weights for several months to create a thick, dark concentrated liquid. You can squeeze the leaves together in a bucket or tube and drain the concentrated liquid into a bottle for storage. Dilute concentrate to a ratio of 1 part concentrate to 40 parts water.

Compost: Fresh leaves help balance the nitrogen-to-carbon ratio in the compost and accelerate decomposition.

Ground comfrey: Dried comfrey leaves can easily be crumbled into comfrey powder. Rake the powder in a prepared bed a few weeks before planting.

Green manure: Comfrey can be grown as a green manure by plowing the foliage into the ground when the plant is still young, which brings valuable biomass and nutrients back into the soil. This method is not without its problems, which we will get into later.

Biodiversity: Comfrey flowers attract pollinators and other beneficial insects. The large leaves also provide shade and moisture to beetles and other insects essential to a healthy ecosystem.

Plant comfrey

Comfrey reproduces best by cuttings or division. Propagation from seeds is usually slow and irregular.

The sowing can be done in the autumn or spring in seed or modular trays for planting out, when all danger of frost has passed. Root cuttings can be taken early in the year and grown in pots or large cell trays in the greenhouse or in a bright, sheltered spot in the garden. Plant divisions can be made in the fall and divisions immediately planted in their new position.

Comfrey plants tolerate most growing conditions, but thrive in full sun to partial shade and on moisture-retaining soils. Space is an important factor to consider before planting comfrey. Comfrey grows vigorously and often doubles every year. Choose a location that has enough space for comfrey to grow and where it doesn't overshadow other plants.

Container growing is a great option when you are short on space. Grow comfrey in large, deep containers that accommodate the plant's deep taproot. Raised beds are another excellent option that includes the roots. However, grow bags may not be ideal and will require plenty of water to keep your plant happy.


Comfrey leavesThe large leaves of comfrey make a great green mulch. Source: Terrie Schweitzer

Here are some tips for growing comfrey at home, although this incredible plant is more or less taking care of itself.

Sun and temperature

Comfrey grows best in full sun to partial shade and requires at least 3-4 hours of direct sunlight per day. In hot climates, plant comfrey where there is shade during the hottest time of the day. Suitable for growing in USDA Zone 4-9 with temperatures from -40 ° F to 80 ° F.

If exposed too early in the season, your plant can wither and suffer frost damage in high temperatures. As an herbaceous perennial, this plant will appear early in the year if the conditions are right. Nevertheless, it benefits from fleece or frost coverings when late frosts are predicted.

Water and moisture

Comfrey enjoys moist soil conditions, but is also surprisingly drought tolerant. The taproots can access water deep in the soil that other plants cannot. Watering with soaking tubes once a week is ideal. Watering when the plant begins to die in winter is not necessary.


Loamy, well-drained but moisture retentive soil is best for growing comfrey, but it will tolerate most types of soil, including heavy loam or sandy soils. The deep-rooted comfrey roots help break up clay soils in preparation for other crops to be grown. Recommended soil pH, 6.0 – 7.0.


Comfrey can tolerate poor soil conditions. It will eventually improve the soil by decomposing its own foliage. If your plant is struggling to establish itself, feed the comfrey with a liquid algae fertilizer or a balanced, low potency organic granular fertilizer. Most of its needs will be nitrogen based for good leaf development, but the other nutrients are important for flowering.


Comfrey grows rapidly during the spring and summer months. The leaves can be cut back to ground level 3-4 times per season and used as fertilizer, mulch, etc. The leaves are ready for harvest again within 4 – 6 weeks. If comfrey plants are left untrimmed, the flowering stems will become weak and collapse at the bottom. Regrowth occurs naturally and shortly thereafter. What you have left is a big messy, unattractive comfrey mess. Regular pruning will keep your comfrey bed clean, tidy and easier to work with.

When you grow Symphytum officinale, pruning before the flowers set seeds will limit the number of home-sown comfrey plants that will appear in your garden.

Comfrey seed headYour comfrey can aggressively self-seed once it develops seed heads. Source: mwms1916


Symphytum officinale can be propagated by seeds, root cuttings and division. Symphytum x uplandicum flower seeds are sterile, so root cuttings and division are the main options for varieties of this species.

Seeds can be sown in seed or modular trays in spring, although germination can be slow and erratic. Keep the seedlings moist and plant them in their final growing positions after all threats of frost have passed.

Root cuttings can be taken in spring and autumn. Simply dig up part of the plant and cut off the amount of roots you need. Cut the roots into 1 inch lengths and plant 1 inch deep in a pot filled with compost. Cover with 2.5 cm of compost and keep moist. When shoots appear and roots protrude from the bottom of the pot, they are ready to be planted out.

Propagation from root cuttings is very easy as almost all parts of the roots produce new plants. This can create problems for people looking to grow comfrey as a green manure, resulting in a plethora of new crops that are difficult to eradicate. When moving a fully grown plant to a new location, dig up the entire root ball, as even a little bit of root residue will grow back and multiply.

Plants can be divided in autumn and divisions immediately planted in their new location. Simply dig up the entire plant and use a spade to cut through the comfrey crown to make the divisions.


Spent Comfrey FlowersAs soon as flowering ends, the flowers fall down to expose the seed head. Source: amortize

Comfrey can be affected by a few common problems. Here are a few things to look out for.

Growing problems

Adult comfrey plants can become stubborn in the garden and look messy if not kept in shape. Cut the plants back to ground level 3-4 times per season and you will be rewarded with excellent nutrient-rich mulch and natural fertilizer.

Share your comfrey every few years helps keep its slow but persistent spread under control.


Snails and snails attack young comfrey sprouts when they emerge, engulfing them completely, leaving holes in the stems. Look out for the signature glistening trail of slime as evidence. Reduce populations by removing their day hiding places and breeding grounds such as damp wet wood and weed mats. Remove by hand after visual contact (best results at night) or drop beer or oatmeal traps, which can be collected and disposed of in the morning. As a last resort, use organic snail pellets. Read the label carefully to make sure it does not harm other wildlife or pets.


Powdery mildew Thrives in high humidity and leaves a thick white fungus on the leaves, which inhibits photosynthesis and hinders growth. Maintain good garden hygiene and remove infected leaves to prevent the disease from spreading and re-infecting in years to come. Make sure there is sufficient sunlight and good air circulation. Treat affected plants with an organic fungicide such as copper fungicide, sulfur, or potassium bicarbonate before or at the first sight of the disease.

Comfrey rust is a fungal disease that weakens plants and inhibits growth. It appears as orange spots on the leaves that contain spores that can infect neighboring plants. Remove infected leaves at first sight and throw them away. Do not compost them as the spores overwinter in soil and compost heaps and can re-infect plants the following year. Applying copper fungicide can slow the recurrence. Russian comfrey tends to be more resilient than other species.

frequently asked Questions

Q: Why is comfrey illegal in the US?

A: It's not illegal to grow comfrey in the United States. The sale of comfrey as a medicinal herb for internal use is prohibited, however, since the pyrrolizidine alkaloids contained in the leaves cause severe liver damage when taken internally and can even be absorbed through the skin when used as a medicinal poultice. This is a great plant to grow in gardens for all of its permaculture benefits, but comfrey use as a medicinal herb is not recommended.

Q: Is comfrey a good fertilizer?

A: Comfrey is rich in nutrients, which makes it an excellent fertilizer for fruit and flowering plants.

Q: is comfrey safe for pets?

A: Comfrey is not safe for pets for the same reason it is prohibited for human consumption. The pyrrolizidine alkaloids are just as harmful for animals. Pets should be kept away from comfrey plants if they have a tendency to nibble on plant leaves.

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