Horticulture Magazine

Comfrey Plant Care & Growing Tips

purple Symphytum officinale L. flowers

Comfrey Overview

Official Plant NameSymphytum officinale
Common Name(s)Comfrey, Boneset, Knit bone
Plant TypePerennial / Herb
Native AreaEurope, Asia, North America
Hardiness RatingH7
ToxicityMedicinal but can be toxic, care required
FoliageDeiciduous
FlowersGenerally purple, pink, blue or cream-coloured
When To SowMarch, April, May, September, October, November
Flowering MonthsJune, July, August
When To PruneJune, August, September
Sunlight

Preferred
Full Sun or Partial Shade

Exposure
Exposed or Sheltered

Size

Height
1 – 1.5M

Spread
1 – 1.5M

Bloom Time
June – August

Soil

Preferred
Most soil types

Moisture
Moist but well drained

pH
Any

Plain and humble, yet bursting with goodness and vitality – that’s Comfrey in a nutshell.

Though the small flowers possess their own rustic charm, this plant’s virtues are wholly practical.

It is renowned for improving soil health, and its nutrient-rich foliage provides raw material for high-quality compost and fertiliser, while herbalists value Comfrey for its topical healing qualities.

Humble and Unsung

The Comfrey, native to the United Kingdom, is one of the more humble and unsung members of the Plant Kingdom.

Not by any stretch a glamour plant that you will find in a stylish flower garden, Comfrey is the floral equivalent of a cult classic movie. Thus – though it is indeed relatively unsung and even humble – this deciduous perennial has its own limited but very devoted following among wise, ‘back to nature’ gardeners. 

For the most part, Comfrey’s cult status is not because of its ornamental oomph but because of its lengthy list of practical uses. As such, in reality, the subject of this gardening guide does not need to be quite so humble nor should it go so totally unsung!

Comfrey is the informal name for 26 or 27 species and established hybrids in Genus Symphytum, a member of the Borage Family (Family Boraginaceae).

They attain heights of about half a metre to just over one metre.

comfrey growing wild in Scotland
Comfrey Plant Growing Wild in Scotland

Plant Characteristics

The different species’ foliage occurs in somewhat different shades of green, including bright medium green, deep dark green, and glazed greyish-green. However, all share a common distinctive feature in that the foliage – leaves, stalks and petioles – is visibly and palpably hairy.

The leaves, deeply etched with veins, are elliptical and 20 to 25 centimetres in length. Those of Symphytum officinale have a more pronounced elliptical shape than those of other varieties.

In May and June the plants produce one-to-two-centimetre pendent flowers shaped like tubular bells.

In shades of cream, yellowish, lilac, purple or pink, they are sometimes bicoloured with the upper or basal half being white or off-white and the lower or outward half in some shade of blue, pink, or purple.

Apart from foliage and the flowers, Comfrey is one of those rare plants whose underground parts merit a few words.

It has rhizomatous fleshy roots, the upper parts of which resemble tuberous vegetables or root vegetables.

Among these is a long taproot that penetrates very deeply so as to ‘tap’ potassium, calcium and other mineral elements from deep down, bringing these up to the foliage (which is the reason that Comfrey leaves are rich in minerals and chemical compounds).

In addition, the mature plant’s root system is well-formed and extensive.

All said, though Comfrey will never be a star – let alone a superstar – in any garden, it plays such a superlative, practically-oriented, supporting role that it is a shoo-in to win multiple Best Supporting role awards!

purple tubular bells of the comfrey plant
Clusters of Purple Tubular Bells – the Flower of the Comfrey Plant

Background and Origins

As a medicinal plant, Comfrey has an established history that goes back many centuries. Though it may well have been used back in 1000 B.C., the earliest known record dates from about 450 B.C. – Herodotus, famed for his The Histories, praised it as a coagulant that stopped even excessive bleeding.

Not quite that far back, the Materia Medica authored in about 75 A.D. by Pedanius Dioscorides, an ancient Greek physician, outlines Comfrey’s uses as a bone-setting agent, a wound healing and sealing agent, and an anti-inflammatory.

In fact, Dioscorides, employed by Imperial Rome, actually used Common Comfrey to heal fractures, wounds, and other battle injuries sustained by Rome’s soldiery.

Comfrey is further known as Knitbone in the English-speaking world and is also called Boneset in the British Isles.

Symphytum officinale or Common Comfrey has become naturalised in the plains states of the United Kingdom and in a few regions of South America.

Plants of this species were likely carried by the earliest British, Spanish, and other European migrants to the New World for their medicinal value.

Symphytum genus Comfreys are not to be confused with Wild Comfrey, as one finds all over the Net.

‘Wild Comfrey’ is, in fact, the common name of Cynoglossum virginianum, a plant that is native to the United States. It is related to Symphytum Comfreys as it too is a member of the Borage Family. 

common comfrey growing naturally in wild grasslands
Common Comfrey Growing Naturally in the Wild

Common Varieties

S. officinale or Common Comfrey has a clumping and spreading habit. It is native to the British Isles and other regions of Europe. It typically reaches a height of over one metre. Its flowers are either cream or in a colour in the pink through purple spectrum. This same species that produces blue flowers is identified by a specific name, S. officinale Blue-Flowered or Blue-Flowered Common Comfrey.

bright blue comfrey flowers with dark green foliage in the background
Blue-Flowered Common Comfrey Sometimes Bears Rich Blue Flowers

S. caucasicum or Caucasian Comfrey has an erect habit and spreads rapidly. It is native to Iran, Georgia, and surrounding regions of Eurasia. It attains a height of about 60 centimetres. It bears lilac-blue flowers that are frequently pink as buds.

S. grandiflorum or Dwarf Comfrey has a bushy habit and is one of the less-invasive species and is found in Georgia and the Caucasus. It may reach a height of only about 40 centimetres with a spread of 60. Flowers are a rich cream shade but are an equally rich pink as buds.

S. ibericum or Iberian Comfrey is another dwarf species but has a spreading, branching habit. It originates from Turkey and the surrounding Caucasus region. It too reaches a height of about 40 centimetres with a spread of about 60. Its flowers are off-white or yellowish-white while the buds are rose-red.

S. × uplandicum or Russian Comfrey is a sterile hybrid and, therefore, cannot self-seed which greatly reduces the concern one has about Comfrey’s invasiveness. However, it exhibits very vigorous growth and, as such, can spread. It can reach a height of nearly 2 metres. Because of the overall size this hybrid attains it is a top choice for harvesting leaves for composting and other practical purposes. Its flowers are among the most appealing too, being of a pretty purple-to-violet hue. 

pink Russian Comfrey flowers
The Pretty Magenta Tube-Bells of Symphytum uplandicum or Russian Comfrey

S. × uplandicum ‘Bocking #14’ is a very popular variety and ‘the smart choice.’ The reason is that it carries all the advantages of the plant without any downside. Like the parent hybrid it is sterile and cannot self-seed but on top of that it is a well-behaved, non-invasive variety that does not spread so much. It reaches a height and spread of (only) about one metre. It bears the same pretty purple-to-violet flowers as the parent hybrid.

S × uplandicum ‘Variegatum’ carries a different set of plusses. It too is sterile and ‘well-behaved’ with a clumping, non-spreading habit. It attains a height and spread of 80 centimetres to a metre. Like Common Comfrey its flowers are in the pink through purple spectrum. Unlike Common Comfrey, its leaves are variegated, displaying fairly thick cream-yellow edging. Did we say that Comfrey plants are not at all ornamental? Oops! 

S. grandiflorum ‘Goldsmith’ or Comfrey Goldsmith is the grandiflorum species’s contribution to Comfrey ornamentation. It has a bushy, clump-forming habit and is one of the dwarf varieties at about 40 centimetres in height with a somewhat smaller spread. The flowers are pastel purple at the basal or upper half and white at the lower or distal half. The variegated leaves are a much brighter shade of green than other Comfreys with an equally bright yellow, very broad and irregular, edging. 

S. Hidcote ‘Pink’ or Comfrey Hidcote Pink has a bushy, clump-forming habit and it does not get out of hand as much as a few of the species can. Its height is as tidy as its habit, being only 40 to 50 centimetres. Its bicoloured flowers are cream at the basal end and a rich bright pink on the outer or distal half. It has an earlier blooming season than other Comfreys. S. Hidcote ‘Blue’ is a variant that bears blue-to-purple flowers.

comfrey leaves being cut into a bucket to make compost
An Excellent Liquid Compost can be made from the Foliage of any Comfrey Variety

Habitat and Growing Conditions

Symphytum species are found throughout Eurasia, from the United Kingdom and Spain east up to West Siberia in the north and Iran to the south.

Moist ground, especially along riverbanks and waterways, is this genus’s preferred habitat. It is also found in the grasslands and steppes of the Caucasus.

A soil pH of Slightly Acidic to Neutral i.e. 6.1 to 7.3 is considered to be ideal for Symphytums though this tough plant will do well in any soil pH from about 5.1 to 8.4, which is a very wide range.

A fully hardy plant, almost all species are hardy down to H7.

Where to Plant Comfrey

Comfrey self-selects itself for cottage gardens, wildflower gardens, and kitchen gardens by virtue of its unglamourous but brimming-with-health, appealing appearance combined with its beneficial value.

Estate gardens and courtyard gardens? Probably not!

While the sterile and non-spreading varieties can be grown in open ground, it may be wise to grow the self-seeding and rapidly-spreading species in large containers.

thick fleshy roots of comfrey plant in a wicker basket
Comfrey Plants have Thick, Fleshy Roots

Feeding, Care and Growing Tips

You really don’t need to ‘grow’ Comfrey – this vigorous plant will grow by itself. Indeed, occasionally some species become invasive and hard to eradicate.

A rich, fertile loam, which may be a balanced mix of sand, chalk, clay and organic manure, is ideal for Comfrey.

Good drainage is preferable but Comfrey is one of those plants that can live with poorly-drained soils. They prefer consistently moist – though not waterlogged – soil.

The species prefer part shade or dappled sunlight whereas some cultivars do best in full sun.

It is not exactly straightforward to grow Comfrey from seeds because for one thing they need a chilling period and for another they are slow to germinate and seedlings take their time to grow and mature.

However, it is incredibly easy to propagate this plant by separation of offsets, crown division, root division, and root cuttings.

What is more, the desirable sterile hybrids cannot be grown from seed at all.

If growing from seed, sow them one to two centimetres deep in a planter or container otherwise they may be sown in a bed.

Seeds should be sown about a fortnight before the last predicted frost date. After sowing, give the planted area a good watering. Thereafter, the soil should be kept moist until seedlings sprout in about 20 days. 

A simpler, hybrid method (involving crown division, root division, and de facto root cuttings) to propagate Comfrey is outlined underneath.

The second half of spring is the ideal time to propagate Comfrey, though, depending on which exact method you use, this plant can be propagated any time of the year.

Choose a mature, established plant.

Dig down about 7.5 to 10 centimetres so as to expose the root system, and clear the soil partway around. Using a sterilised sharp knife, carefully and cleanly slice horizontally across the root system and remove the plant, which will come away with the 7.5 to 10 centimetres of the fleshy roots and root system that you had exposed. 

Lightly cover the dug-up area with soil, and water it well. Keep that area moist and the plant will regenerate from the roots in a few weeks.

Depending on the size and branching of the plant, you can separate it by cutting it vertically into two, three or even four sections, each with foliage, stem, and roots. As always, use a sharp, sterilised knife.

Selectively remove leaves as necessary, retaining a mix of mature leaves and young leaves. Then transplant the sections and water them well. Continue to keep the soil moist, and you will have new Comfrey plants.

Typically, one doesn’t fertilise Comfrey but it will benefit by an annual application of organic compost.

Glass Comfrey tincture
The Comfrey Plant: Dried Root, Foliage, and Flower – and Medicinal Compound!

Harvesting and Pruning Comfrey

Avoid harvesting the leaves for the first year so that the plant’s root system can develop and get established.

You can harvest the foliage after the plant has reached half its maximum height.

Do so by grasping a handful of leaves and cutting them 8 to 10 centimetres off the ground using a sharp knife or largeish pruning shears.

If you like Comfrey flowers, cut back the stems after flowering is done and you may get a rebloom.

Common Diseases and Problems

Comfrey is a remarkably disease-free plant.

Slugs and snails may attack it and occasionally it can succumb to powdery mildew but that’s about it in the United Kingdom.

Where to Buy Comfrey

A plain jane this plant might be but some or another variety will be found at your neighbourhood nursery. The larger garden centres stock most of the varieties listed above.

As a plant with potent medicinal value, numerous Comfrey varieties are available online.

In any event, if a friend or relative has Comfrey, you don’t need to buy it. Simply get a 15-centimetre root cutting and you’ll have a new Comfrey plant!

beinwell leaves
The Mid-Green Leaves of Common Comfrey Show Deeply Etched Veins

Comfrey Uses In The Garden

Unlike many other plants that have beneficial qualities, Comfrey’s virtues do not fall within one single area, such as medicinal uses, health benefits, or garden purposes.

The qualities of this plant, particularly Common Comfrey, are such that the benefits are scattered in all these different areas. 

It is to be noted that Comfrey varieties are loaded with, among many compounds, allantoin and pyrrolizidine alkaloids. 

Comfrey tea, a liquid compost, is made by immersing or steeping leaves for about three weeks. It is also obtained as a composting byproduct by rotating and decomposing leaves in a composting tumbler.

Comfrey tea, especially high in potassium, is very concentrated and, therefore, must be diluted in about 15 parts of water to make a liquid fertiliser.

The most frequent and well-known use of this plant is for the preparation of high-quality mulch, compost and fertiliser, as the foliage contains significant amounts of nitrogen, phosphorous and potassium.

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