Comfrey
Encyclopedia
Comfrey is an important herb
in organic gardening. It is used as a fertilizer and also has many purported medicinal uses. The main species used now is
Symphytum × uplandicum or Russian comfrey, a hybrid between Symphytum officinale
(common comfrey) and Symphytum asperum
(rough comfrey).
L.) is a perennial herb of the family
Boraginaceae
with a black, turnip-like root and large, hairy broad leaves that bears small bell-shaped flowers of various colours, typically cream or purplish, which may be striped. It is native to Europe
, growing in damp, grassy places, and is locally frequent throughout Ireland and Britain on river banks and ditches. More common is the hybrid between S. offinale and S. asperum
, Symphytum × uplandicum, known as Russian Comfrey, which is widespread in the British Isles, and which interbreeds with S. officinale. Compared to S. officinale, S. × uplandicum is generally more bristly and has flowers which tend to be more blue or violet.
Comfrey has long been recognised by both organic gardeners and herbalists for its great usefulness and versatility; of particular interest is the 'Bocking 14' cultivar of Russian Comfrey. This strain was developed during the 1950s by Lawrence D Hills
, the founder of the Henry Doubleday Research Association (the organic gardening organisation itself named after the Quaker pioneer who first introduced Russian Comfrey into Britain in the 1910s) following trials at Bocking
, near Braintree
, the original home of the organization.
or mildew
. When dividing comfrey plants, take care not to spread root fragments around, or dispose of on the compost
heap, as each can re-root, and comfrey can be a very difficult plant to get rid of. Offsets can also be purchased by mail order from specialist nurseries in order to initially build up a stock of plants.
if available. Offsets should be planted 2–3 feet apart with the growing points just below the surface, whilst root segments should be buried about 2 inches deep. Keep the bed well watered until the young plants are established. Comfrey should not be harvested in its first season as it needs to become established. Any flowering stems should be removed as these will weaken the plant in its first year.
Comfrey is a fast growing plant, producing huge amounts of leaf during the growing season, and hence is very nitrogen
hungry. Although it will continue to grow no matter what, it will benefit from the addition of animal manure applied as a mulch, and can also be mulched with other nitrogen rich materials such as lawn mowings, and is one of the few plants that will tolerate the application of fresh urine
diluted 50:50 with water, although this should not be regularly added as it may increase salt levels in the soil and have adverse effects on soil life
such as worm
s. Mature comfrey plants can be harvested up to four or five times a year. They are ready for cutting when about 2 feet high, and, depending on seasonal conditions, this is usually in mid-Spring. Comfrey will rapidly regrow, and will be ready for further cutting about 5 weeks later. It is said that the best time to cut comfrey is shortly before flowering, for this is when it is at its most potent in terms of the nutrients that it offers. Comfrey can continue growing into mid-Autumn, but it is not advisable to continue taking cuttings after early Autumn in order to allow the plants to build up winter reserves. As the leaves die back and break down in winter, nutrients and minerals are transported back to the roots for use the following spring.
Comfrey should be harvested by using either shears
, a sickle
, or a scythe
to cut the plant about 2 inches above the ground, taking care handling it because the leaves and stems are covered in hairs that can irritate the skin. It is advisable to wear gloves when handling comfrey. Despite being sterile, Bocking 14 Russian Comfrey will steadily increase in size. It is therefore advisable to split it up every few years (and at the same time propagate more plants that can be shared with fellow gardeners!). It is however difficult to remove comfrey once established as it is very deep rooting, and any fragments left in the soil will regrow. Rotovation can be successful, but may take several seasons. The best way to eradicate comfrey is to very carefully dig it out, removing as much of the root as possible. This is best done in hot, dry summer weather, wherein the dry conditions will help to kill off any remaining root stumps. Comfrey is generally trouble free once established, although weaker or stressed plants can suffer from comfrey rust or mildew. Both are fungal
diseases, although they rarely seriously reduce plant growth and thus do not generally require control. However infected plants should not be used for propagation purposes.
One of the country names for comfrey was ‘knitbone’, a reminder of its traditional use in healing bone fractures. Modern science confirms that comfrey can influence the course of bone ailments.
The herb contains allantoin
, a cell proliferant that speeds up the natural replacement of body cells. Comfrey was used in an attempt to treat a wide variety of ailments ranging from bronchial problems, broken bones, sprains, arthritis, gastric and varicose ulcers, severe burns, acne and other skin conditions. It was reputed to have bone and teeth building properties in children, and have value in treating "many female disorders". Constituents of comfrey also include mucilage
, steroid
al saponin
s, tannin
s, pyrrolizidine alkaloids, inulin
, and protein
s.
Internal usage of comfrey should be avoided because it contains hepatotoxic
pyrrolizidine alkaloids (PAs). Use of comfrey can, because of these PAs, lead to veno-occlusive disease (VOD). VOD can in turn lead to liver
failure, and comfrey, taken in extreme amounts, has been implicated in at least one death. In 2001, the United States
Food and Drug Administration
issued a warning against internal usage of herbal products containing comfrey. There are ways to remove the pyrrolizidine alkaloids from comfrey, and some herbal product manufacturers have begun doing so (although the products will still be labelled “for external use only”).
Excessive doses of symphytine, one of the PAs in comfrey, may cause cancer
in rats. This was shown by injection of the pure alkaloid. The whole plant has also been shown to induce precancerous changes in rats.
Most recently, in a placebo controlled study comfrey was found to decrease back pain when used topically. However, it is not clear if these results reached statistical significance
.
, mining a host of nutrients from the soil. These are then made available through its fast growing leaves (up to 4-5 pounds
per plant per cut) which, lacking fibre, quickly break down to a thick black liquid. There is also no risk of nitrogen robbery when comfrey is dug into the soil as the C:N ratio
of the leaves is lower than that of well-rotted compost. Comfrey is an excellent source of potassium
, an essential plant nutrient needed for flower
, seed
and fruit
production. Its leaves contain 2-3 times more potassium than farmyard manure, mined from deep in the subsoil
, tapping into reserves that would not normally be available to plants.
There are various ways in which comfrey can be utilised as a fertiliser, these include:
Herb
Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...
in organic gardening. It is used as a fertilizer and also has many purported medicinal uses. The main species used now is
Symphytum × uplandicum or Russian comfrey, a hybrid between Symphytum officinale
Symphytum officinale
Symphytum officinale is a perennial flowering plant of the genus Symphytum in the family Boraginaceae. Along with several other species of Symphytum, it is commonly known as comfrey. To differentiate it from other comfreys, this species may be known as common comfrey, Quaker comfrey, and cultivated...
(common comfrey) and Symphytum asperum
Symphytum asperum
Symphytum asperum is a flowering plant of the genus Symphytum in the family Boraginaceae. Common names include rough comfrey and prickly comfrey. It is native to Asia and it is known in Europe and North America as an introduced species and sometimes a weed.-References:* -External links:**...
(rough comfrey).
Description
Comfrey (Symphytum officinaleSymphytum officinale
Symphytum officinale is a perennial flowering plant of the genus Symphytum in the family Boraginaceae. Along with several other species of Symphytum, it is commonly known as comfrey. To differentiate it from other comfreys, this species may be known as common comfrey, Quaker comfrey, and cultivated...
L.) is a perennial herb of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Boraginaceae
Boraginaceae
Boraginaceae, the Borage or Forget-me-not family, include a variety of shrubs, trees, and herbs, totaling about 2,000 species in 146 genera found worldwide.A number of familiar plants belong to this family....
with a black, turnip-like root and large, hairy broad leaves that bears small bell-shaped flowers of various colours, typically cream or purplish, which may be striped. It is native to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, growing in damp, grassy places, and is locally frequent throughout Ireland and Britain on river banks and ditches. More common is the hybrid between S. offinale and S. asperum
Symphytum asperum
Symphytum asperum is a flowering plant of the genus Symphytum in the family Boraginaceae. Common names include rough comfrey and prickly comfrey. It is native to Asia and it is known in Europe and North America as an introduced species and sometimes a weed.-References:* -External links:**...
, Symphytum × uplandicum, known as Russian Comfrey, which is widespread in the British Isles, and which interbreeds with S. officinale. Compared to S. officinale, S. × uplandicum is generally more bristly and has flowers which tend to be more blue or violet.
Comfrey has long been recognised by both organic gardeners and herbalists for its great usefulness and versatility; of particular interest is the 'Bocking 14' cultivar of Russian Comfrey. This strain was developed during the 1950s by Lawrence D Hills
Lawrence D Hills
Lawrence D. Hills was a British horticulturalist, journalist, and writer, founder of the Henry Doubleday Research Association Bocking, near Braintree, Essex in 1954, now Garden Organic...
, the founder of the Henry Doubleday Research Association (the organic gardening organisation itself named after the Quaker pioneer who first introduced Russian Comfrey into Britain in the 1910s) following trials at Bocking
Bocking
Bocking can refer to:*Bocking, a village near Braintree, Essex*Bocking 14, a cultivated strain of the plant Comfrey*Powerbocking, the use of powered stilts patented by Alexander Böck...
, near Braintree
Braintree, Essex
Braintree is a town of about 42,000 people and the principal settlement of the Braintree district of Essex in the East of England. It is northeast of Chelmsford and west of Colchester on the River Blackwater, A120 road and a branch of the Great Eastern Main Line.Braintree has grown contiguous...
, the original home of the organization.
Propagation
Bocking 14 is sterile, and therefore will not set seed (one of its advantages over other cultivars as it will not spread out of control), thus is propagated from root cuttings. The gardener can produce their own ‘offsets’ from mature, strongly growing plants by driving a spade horizontally through the leaf clumps about 3 inches below the soil surface. This removes the crown, which can then be split into pieces. The original plant will quickly recover, and each piece can be replanted with the growing points just below the soil surface, and will quickly grow into new plants. When choosing plants to divide, ensure that they are strong healthy specimens with no signs of rustRust (fungus)
Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales. About 7800 species are known. Rusts can affect a variety of plants; leaves, stems, fruits and seeds. Rust is most commonly seen as coloured powder, composed off tiny aeciospores which land on vegetation producing...
or mildew
Mildew
Mildew refers to certain kinds of molds or fungi.In Old English, it meant honeydew , and later came to mean mildew in the modern sense of mold or fungus....
. When dividing comfrey plants, take care not to spread root fragments around, or dispose of on the compost
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...
heap, as each can re-root, and comfrey can be a very difficult plant to get rid of. Offsets can also be purchased by mail order from specialist nurseries in order to initially build up a stock of plants.
Cultivation
The comfrey bed should be well prepared by weeding thoroughly, and dressing with manureManure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...
if available. Offsets should be planted 2–3 feet apart with the growing points just below the surface, whilst root segments should be buried about 2 inches deep. Keep the bed well watered until the young plants are established. Comfrey should not be harvested in its first season as it needs to become established. Any flowering stems should be removed as these will weaken the plant in its first year.
Comfrey is a fast growing plant, producing huge amounts of leaf during the growing season, and hence is very nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
hungry. Although it will continue to grow no matter what, it will benefit from the addition of animal manure applied as a mulch, and can also be mulched with other nitrogen rich materials such as lawn mowings, and is one of the few plants that will tolerate the application of fresh urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
diluted 50:50 with water, although this should not be regularly added as it may increase salt levels in the soil and have adverse effects on soil life
Soil life
Soil life or soil biota is a collective term for all the organisms living within the soil.-Overview:In balanced soil, plants grow in an active and steady environment. The mineral content of the soil and its heartiful structure are important for their well-being, but it is the life in the earth that...
such as worm
Worm
The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...
s. Mature comfrey plants can be harvested up to four or five times a year. They are ready for cutting when about 2 feet high, and, depending on seasonal conditions, this is usually in mid-Spring. Comfrey will rapidly regrow, and will be ready for further cutting about 5 weeks later. It is said that the best time to cut comfrey is shortly before flowering, for this is when it is at its most potent in terms of the nutrients that it offers. Comfrey can continue growing into mid-Autumn, but it is not advisable to continue taking cuttings after early Autumn in order to allow the plants to build up winter reserves. As the leaves die back and break down in winter, nutrients and minerals are transported back to the roots for use the following spring.
Comfrey should be harvested by using either shears
Shears
Shears may mean:* trauma shears, scissors used by emergency medical personnel to quickly and safely cut clothing* kitchen shears, a kind of scissors* pinking shears, a kind of scissors* blade shears, typically used for shearing animals...
, a sickle
Sickle
A sickle is a hand-held agricultural tool with a variously curved blade typically used for harvesting grain crops or cutting succulent forage chiefly for feeding livestock . Sickles have also been used as weapons, either in their original form or in various derivations.The diversity of sickles that...
, or a scythe
Scythe
A scythe is an agricultural hand tool for mowing grass, or reaping crops. It was largely replaced by horse-drawn and then tractor machinery, but is still used in some areas of Europe and Asia. The Grim Reaper is often depicted carrying or wielding a scythe...
to cut the plant about 2 inches above the ground, taking care handling it because the leaves and stems are covered in hairs that can irritate the skin. It is advisable to wear gloves when handling comfrey. Despite being sterile, Bocking 14 Russian Comfrey will steadily increase in size. It is therefore advisable to split it up every few years (and at the same time propagate more plants that can be shared with fellow gardeners!). It is however difficult to remove comfrey once established as it is very deep rooting, and any fragments left in the soil will regrow. Rotovation can be successful, but may take several seasons. The best way to eradicate comfrey is to very carefully dig it out, removing as much of the root as possible. This is best done in hot, dry summer weather, wherein the dry conditions will help to kill off any remaining root stumps. Comfrey is generally trouble free once established, although weaker or stressed plants can suffer from comfrey rust or mildew. Both are fungal
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
diseases, although they rarely seriously reduce plant growth and thus do not generally require control. However infected plants should not be used for propagation purposes.
Medicinal uses
Contemporary herbalists view comfrey as an ambivalent and controversial herb that may offer therapeutic benefits but can cause liver toxicity.One of the country names for comfrey was ‘knitbone’, a reminder of its traditional use in healing bone fractures. Modern science confirms that comfrey can influence the course of bone ailments.
The herb contains allantoin
Allantoin
Allantoin is a chemical compound with formula C4H6N4O3. It is also called 5-ureidohydantoin or glyoxyldiureide. It is a diureide of glyoxylic acid....
, a cell proliferant that speeds up the natural replacement of body cells. Comfrey was used in an attempt to treat a wide variety of ailments ranging from bronchial problems, broken bones, sprains, arthritis, gastric and varicose ulcers, severe burns, acne and other skin conditions. It was reputed to have bone and teeth building properties in children, and have value in treating "many female disorders". Constituents of comfrey also include mucilage
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
, steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
al saponin
Saponin
Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species...
s, tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...
s, pyrrolizidine alkaloids, inulin
Inulin
Inulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
, and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s.
Hepatotoxicity
Hepatotoxicity implies chemical-driven liver damage.The liver plays a central role in transforming and clearing chemicals and is susceptible to the toxicity from these agents. Certain medicinal agents, when taken in overdoses and sometimes even when introduced within therapeutic ranges, may injure...
pyrrolizidine alkaloids (PAs). Use of comfrey can, because of these PAs, lead to veno-occlusive disease (VOD). VOD can in turn lead to liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
failure, and comfrey, taken in extreme amounts, has been implicated in at least one death. In 2001, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
issued a warning against internal usage of herbal products containing comfrey. There are ways to remove the pyrrolizidine alkaloids from comfrey, and some herbal product manufacturers have begun doing so (although the products will still be labelled “for external use only”).
Excessive doses of symphytine, one of the PAs in comfrey, may cause cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
in rats. This was shown by injection of the pure alkaloid. The whole plant has also been shown to induce precancerous changes in rats.
Most recently, in a placebo controlled study comfrey was found to decrease back pain when used topically. However, it is not clear if these results reached statistical significance
Statistical significance
In statistics, a result is called statistically significant if it is unlikely to have occurred by chance. The phrase test of significance was coined by Ronald Fisher....
.
Fertilizer uses
Comfrey is a particularly valuable source of fertility to the organic gardener. It is very deep rooted and acts as a dynamic accumulatorDynamic accumulator
Dynamic accumulators are plants that mine nutrients from the soil through their roots. These plants can then be used as a fertiliser, or as part of a fertiliser mix, for other plants that may be deficient in those particular nutrients...
, mining a host of nutrients from the soil. These are then made available through its fast growing leaves (up to 4-5 pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
per plant per cut) which, lacking fibre, quickly break down to a thick black liquid. There is also no risk of nitrogen robbery when comfrey is dug into the soil as the C:N ratio
Carbon to nitrogen ratio
The C/N ratio or carbon-to-nitrogen ratio is a ratio of the mass of carbon to the mass of nitrogen in a substance. It can, amongst other things, be used in analysing sediments and compost...
of the leaves is lower than that of well-rotted compost. Comfrey is an excellent source of potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, an essential plant nutrient needed for flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
, seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
production. Its leaves contain 2-3 times more potassium than farmyard manure, mined from deep in the subsoil
Subsoil
Subsoil, or substrata, is the layer of soil under the topsoil on the surface of the ground. The subsoil may include substances such as clay and/or sand that has only been partially broken down by air, sunlight, water, wind etc., to produce true soil...
, tapping into reserves that would not normally be available to plants.
There are various ways in which comfrey can be utilised as a fertiliser, these include:
- Comfrey as a compost activator - include comfrey in the compost heap to add nitrogen and help to heat the heap. Comfrey should not be added in quantity as it will quickly break down into a dark sludgy liquid that needs to be balanced with more fibrous, carbon rich material.
- Comfrey liquid fertilizer - can be produced by either rotting leaves down in rainwater for 4–5 weeks to produce a ready to use 'comfrey tea', or by stacking dry leaves under a weight in a container with a hole in the base. When the leaves decompose a thick black comfrey concentrate is collected. This must be diluted at 15:1 before use.
- Comfrey as a mulchMulchIn agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....
or side dressing - a 2 inch layer of comfrey leaves placed around a crop will slowly break down and release plant nutrients; it is especially useful for crops that need extra potassium, such as fruit bearers but also reported to do well for potatoes. Comfrey can be slightly wilted before application optionally but either way, avoid using flowering stems as these can root. - Comfrey potting mixture - originally devised to utilize peat, now environmental awareness has led to a leaf moldLeaf moldLeaf mold is a form of compost produced by the fungal breakdown of shrub and tree leaves, which are generally too dry, acidic, or low in nitrogen for bacterial decomposition.-Description:...
-based alternative being adopted instead; two year old, well decayed leaf mold should be used, this will absorb the nutrient-rich liquid released by the decaying comfrey. In a black plastic sack alternate 3-4 inch layers of leaf mold and chopped comfrey leaves. Add a little dolomitic limestoneDolomiteDolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
to slightly raise pHSoil pHThe soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
. Leave for between 2–5 months depending on the season, checking that it does not dry out or become too wet. The mixture is ready when the comfrey leaves have rotted and are no longer visible. Use as a general potting compost, although it is too strong for seedlings.
External links
- Comfrey Central - A Clearinghouse for Symphytum Information
- British Columbia Cancer Agency on comfrey
- PubMed/Medline
- ITIS 32025 2002-09-05.
- NRM, Sweden 2002-09-05.
- IPNI Symphytum 2002-09-05.
- Flora of China 2002-09-05.