Comfrey (Symphytum officinale) is a perennial herb with broad, hairy leaves and clusters of bell-shaped flowers, which can range in colour from purple to cream. Native to Europe and parts of Asia, it has been widely used in traditional medicine for its purported healing properties.
Comfrey contains allantoin, a compound believed to help with skin cell regeneration, and rosmarinic acid, which may have pain-relieving and anti-inflammatory effects. However, due to the presence of toxic pyrrolizidine alkaloids, comfrey is not recommended for internal use and should be used with caution externally. Despite this, comfrey is still valued in organic gardening as a fertilizer and for its ability to improve soil health.
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Comfrey plant names & classification
The botanical name for comfrey is Symphytum officinale. It is commonly known as comfrey and belongs to the plant family Boraginaceae. Other names for comfrey include knitbone, boneset, and bruisewort.
Where can you find comfrey plant
Common comfrey is often found in damp, grassy places such as riverbanks, ditches, in fens, on roadside verges, waste ground and meadows. It is native to Europe and grows in many temperate climates.
In the United States, there is a native species known as wild comfrey (Cynoglossum virginianum), which can be found in habitats such as bottomland forests, moist upland forests, pastures, and along the banks of streams and rivers.
How to identify comfrey plant
- Leaves: Comfrey has large, oval, hairy leaves that are rough in texture.
- Flowers: It produces clusters of drooping, tubular flowers that can be pinky-purple, cream, or even yellow or blue, depending on the variety. The flowers are bell-shaped and may be striped or have a curling cluster that resembles a scorpion’s tail.
- Height: The plant can grow quite tall, typically reaching up to 2-3 feet in height.
- Stems: The stems are winged, with the leaf bases extending down the stem to give it a winged appearance.
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How to use comfrey in cooking
- Young Leaves: These could be eaten cooked or raw. Comfrey leaves are covered in small hairs, which can give them a slightly slimy texture when cooked. Although they may contain minerals, many find the texture and mouthfeel unappealing. If added to salads in small, finely chopped pieces, the hairiness may be less noticeable.
- Young Shoots: Historically, young comfrey shoots might have been prepared and consumed in a similar fashion to asparagus. The pale, tender stalks would be blanched before eating.
- Older Leaves: In the past, older leaves of comfrey were sometimes dried and then steeped to make tea.
- Roots: The roots of comfrey could be peeled, chopped, and added to soups for their purported medicinal properties.
- Tea and Coffee Substitute: A tea might have been made from the dried leaves and roots of comfrey. Additionally, roasted comfrey roots could have been mixed with dandelion and chicory roots to create a coffee-like beverage.
Other uses for comfrey
For garden use, comfrey is excellent as a fertilizer due to its high levels of nitrogen, phosphorus, and potassium. You can make a comfrey feed by steeping the leaves in water to create a nutrient-rich liquid plant food.
How to make comfrey plant feed
- Harvest Comfrey Leaves: Ideally, choose young, vibrant leaves from the comfrey plant, as these contain the highest concentration of nutrients. The best time to harvest is in late spring or early summer when the plant is in its most vigorous growth phase.
- Prepare the Container: Use a large container with a lid, such as a bucket or a barrel. Make sure it’s clean to prevent any contamination of your comfrey feed.
- Fill the Container: Place the comfrey leaves into the container, packing them down. You can chop the leaves to help them break down faster, but this is optional.
- Weight the Leaves Down: Some gardeners recommend placing a weight on top of the leaves to keep them submerged and to help them break down more efficiently.
- Add Water (Optional): While you can make a comfrey feed by simply allowing the leaves to decompose into a slurry, some gardeners prefer to add water to cover the leaves, speeding up the decomposition process and creating a liquid feed.
- Cover the Container: Put the lid on the container to keep out flies and reduce the smell, as the fermentation process can be quite pungent.
- Let It Brew: Allow the comfrey leaves to break down. This process can take anywhere from a few weeks to a couple of months, depending on the temperature and whether or not you’ve added water.
- Strain the liquid: Once the leaves have decomposed into a dark, rich liquid, strain out the solid material. You can use a sieve, cheesecloth, or an old piece of cloth to do this.
- Dilute the feed: The resulting liquid will be very concentrated and should be diluted before use. A common dilution ratio is 10:1 or 15:1, meaning 10 or 15 parts water to one part comfrey feed.
- Use the comfrey feed: Apply the diluted comfrey feed to the soil around your plants. It’s particularly beneficial for flowering and fruiting plants due to its high potassium content.
- Dispose the rest of the leaves: The remaining solid material can be added to your compost heap as it will still contain valuable nutrients.
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Known hazards of using comfrey
Comfrey contains pyrrolizidine alkaloids (PAs), which are known to be hepatotoxic, meaning they can cause liver damage. PAs can also be carcinogenic and have been linked to the development of liver cancer. The toxicity is not just limited to the liver, as PAs can also cause lung damage and harm to other organs.
In the USA comfrey products are being recommended to be removed from the market for internal use, and many health authorities advise against the use of comfrey in any form that involves ingestion. Even external use poses some risk, as PAs can be absorbed through the skin.
Given these significant health risks, it is generally recommended to avoid using comfrey, especially for internal purposes, and to consult with a healthcare professional before using it externally.
When it’s the best time to harvest comfrey
The best time to harvest comfrey typically depends on the intended use, but generally, it can be harvested from late spring through fall. You can chop most of the plants down close to the ground in late June, and since comfrey is a fast grower, it can be harvested again after it regrows. The optimal times for harvesting comfrey leaves are usually in July and September. When harvesting, aim to cut the leaves when the plant is about two feet tall to encourage new growth.
For medicinal use, such as making comfrey salve, fall is a good time to harvest comfrey leaves. Remember to always use comfrey externally, as internal use is not recommended due to the presence of toxic pyrrolizidine alkaloids.
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What can comfrey be confused with?
Comfrey can be confused with several other plants, particularly before flowering, due to similarities in leaf shape and plant structure. Some of the plants that comfrey may be mistaken for include:
- Foxglove (Digitalis purpurea): Young leaves of foxglove can look very similar to those of comfrey in the early spring. However, the flowers of foxglove are distinctly different, being large, tubular, and purple with spots inside. Foxglove is also highly toxic if ingested
- Houndstongue (Cynoglossum officinale): This plant has clusters of small, purple to pink to blue flowers that may resemble comfrey’s flowers, and the leaves can also be similar in appearance
- Green Alkanet (Pentaglottis sempervirens): This plant is related to comfrey and borage and has hairy leaves that look a bit like comfrey, with blue flowers that are similar to those of borage and forget-me-nots
This blog post was originally written on 14 February 2024 and last updated on 14 February 2024
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