It is possible to grow comfrey from seed, but this takes a process of stratification and is often overlooked in favor of taking root cuttings or using crown offsets.
Comfrey can grow to overcrowd even the most generous space and will need care and consideration. However you will be rewarded with a plant that can break up the most soggy of clay soils and bring out any nitrogen that may be deposited lower down.
It really is a useful perennial in any garden, but works very well in a wildlife garden!
Comfrey – 101
Comfrey is a tender perennial in the UK and USDA zones 4-9, to find out your zone have a look here. This means that it will die back each year but come back stronger the following Spring. There are two main types of comfrey that you will harvest at home; Russian Comfrey – for the organic gardener and Common Comfrey for the herbalist.
Russian comfrey is sterile so will not go to seed, however it can still be invasive. Common comfrey is known to propagate by seed, although it can take a few years for the seeds to germinate and produce a mature plant. Neither type of comfrey are grown for human consumption. It is poisonous to eat, but not to use in balms and topical treatments.
You can choose to harvest comfrey when the plant is at around 2 feet in height and use the leaves of both types to feed your soil. If you choose to leave until after the flowers have died back you will have provided food for many predator bugs in your garden. These are positive predators who will feast on the nasty bugs who can destroy a crop. The flowers are also very popular with pollinators and for this reason gardeners choose to allow the herb to go to flower and almost to seed.
When mature common comfrey will grow to be anywhere between 1-3 feet in height and 1 to 2.5 feet in width. The leaves are around 8 inches in length and can be harvested in late Spring or after they have flowered. The flowering period for comfrey is wonderfully long and you can extend it further by pinching out the flowers as they start to fade.
Comfrey will grow happily in partial shade to sun, needing at least 3 hours of sunshine a day, however it will grow with a little less, just not as quickly. As far as soil type goes comfrey is really not a fussy herbaceous perennial and will thrive in clay or sandy conditions. It is invasive so even stone filled soils will allow for the long taproot to thrive.
Comfrey will grow happily in a pot which is large enough to accommodate it’s taproots and which has adequate drainage. The pot can be topped with a manure to give the comfrey a chance to have a moist soil without rotting the roots. If you want to move your comfrey around to allow the bees and other pollinators to be attracted to different parts of your garden.
Growing comfrey in pots is one way to ensure that this happy perennial does not become a monster and take over your garden! Just catch the flowers before they go over and become seed heads. It is possible to harvest seeds by cutting the seed heads off before they get a chance to scatter in the wind, however division is best as it will stop the comfrey from becoming root bound in it’s pot. Part of a healthy clumping perennial like comfrey is a regular division as per our instructions below.
How To Grow Comfrey From Seed
There are several types of comfrey available to purchase with the bocking 14 type being popular with gardeners as a homemade fertilizer. It is sterile and therefore does not produce any seeds. However you may want to grow the variety of comfrey that is suitable for herbalists, symphytum officinale seeds are the perfect variety.
- To mimic winter for your comfrey plant you will need to sow them into a moist growing medium. I love vermiculite for this as it is sterile and will not encourage mold growth, however moist sand is also suitable.
- A little plant feed does a world of good when held in vermiculite and it will just give your comfrey seeds a little extra boost. Germination rates are quite low, so you need to give yourself every chance of success! Don’t get me wrong all you need are a few to germinate and then you can take root cuttings forever more!
- Put them into a zip locked bag and make sure it is really sealed tight! No little people knocking over your seeds in the fridge this way! Your comfrey seeds will need between 30-60 days in the fridge.
- Check to see if the seeds have split after bout day 30, comfrey can take a little longer and this is not uncommon, just make sure there is no developing mold.
- You can then plant your comfrey out where they are to grow germination rates at this stage are both longer and more unpredictable than starting indoors. If you choose to plant directly make sure to dig a healthy amount of loamy organic matter through the soil first.
- Alternatively you can plant your comfrey seeds in biodegradable pots indoors and keep them a little warmer. With the germination rate being a little more predictable you will see your first seedlings emerging after around 10-15 days. Keep them in a sunny spot with plenty of water, but not damp.
- If you live in colder zones, do give them a chance to acclimatize to the outdoors weather, but comfrey will grow fast once it has made it’s first appearance. So get it outside quickly.
- You can grow in pots or directly to the ground. With this variety you will need to dead head the flowers before they become seeds and self sow around your garden. IF you are growing comfrey in pots make sure to use a large pot with deep sides to accommodate that large tap root.
TOP TIP – Comfrey is poisonous and deemed unsafe to consume. This includes all parts above ground and the root system. Therefore it is not enough to be able to identify the leaves and not harvest them for food, but you must also be careful not interplant with herbs and vegetables whose roots you may want to eat! Mainly I am thinking about horseradish and similar sized and colored roots.
How To Propagate Comfrey From Root Cuttings
Comfrey is just that little bit more unusual than other plants when it comes to division. I will walk you through it as I think you will find it worthwhile!
- Start by loosening the soil around your comfrey plant, about a year old will be mature enough to need a bit more space. Using a fork to loosen the soil you can slightly lift the plant and then use a sharp spade to cut the original plant in half from the top.
- The original comfrey plant will do well once you have back filled this new hole with soil and watered well.
- Take your half plant from the division and wash it in a bucket to remove soil and allow for a clean root stock. Comfrey taken this way is ideal for your bocking 14 which is sterile. It will not produce seeds and you can get a pretty much continual crop as your original plant will start to bulk out again almost within a few months.
- Now you are going to be able to take a mixture of comfrey crown offsets and root cuttings.
- In order for your crown offsets to thrive the leaf will need to be cut down to around a 1/2 inch, no more. It looks cruel but you are reducing the stress on the new roots to provide water and nutrients for those large leaves. Use a sharp, clean knife for this and be careful not to cut yourself, so cut away from your hand and body at all times.
- Comfrey is a naturally clumping plant, this means you can pull away the little crown offsets that are around the edge of your stump cutting. You will need a knife to aid you with this, but more to sort of push them away than cut them off.
- The comfrey root and crown offsets will really take very easily. This is similar to mint where if you disturb the roots you will actually accidentally propagate it all around the area you are digging. Comfrey wants to live! So cut your root and crowns to around 3-5 inch chunks. The crown offsets are just the same as the roots, but they have the 1/2 inch of leaves to the top. Yes, they will take more quickly, but it is all worth harvesting and growing on.
- Plant direct to the ground where you want them to grow, this can be beneficial if you are looking to increase an existing comfrey plot. If so space the new cuttings 60cm apart. If you are going to give each new cutting the very best chance plant into compost filled pots and water well, but keep under glass until the fear of frost has passed. The roots offsets should be completely covered, but the crowns should just be showing the tips of the cut leaves at the top of the soil. Then as soon as new leaves start to show, get them into the ground.
- At the same time next year your comfrey is mature and ready to be split again, so use what you want and split the rest.
TOP TIP- Comfrey root is around 6 foot long. This tap root is how the plant can pull up nutrients that other crops may not be able to. Basically this is a wonderful design for getting the most out of any soil type, meaning comfrey will grow in clay soils, sandy soils and even be partially drought tolerant when mature. What it also means is that if you disturb the roots when tilling around the area you are basically propagating it. This will result in an overcrowded flower bed. This is why comfrey is great in it’s own designated bed, or even planted by mature shrubs and trees that won’t require much movement.
Comfrey As A Green Manure
Green manure is a massive part of the organic gardeners arsenal to protect and promote healthy plants. Choosing plants that will aerate and area as well as pull out useful nutrient and process them into a form that other, more common plants can absorb. Comfrey, fenugreek, clover and borage are all fabulous green manures, that also look very pleasing in the winter garden.
What Is Bocking 14 NPK
‘Bocking 14’ is an organic gardeners dream for nutrient fixing in our gardens. It is a type of Russian Comfrey cross with Common Comfrey S. uplandicum that is sterile and therefore will not self seed and invade your entire garden. This variety is different from a herbalists comfrey though, containing high levels of NPK. Bocking 14 is an ideal fertilizer and plant feed.
NPK is made up of Nitrogen (N), Phosphorous (P) and Potassium (K) are all required for full foliage and healthy flower growth. You will find that your plants can absorb more of the sunlight and transform it to chlorophyll much more readily when they have these three key elements in place.
As a member of the borage family we can use it in a similar way;
- Bocking 14, Russian comfrey can be used added to your compost heap. It will add those nutrients that it has been able to pull up from the lower regions of the soil. It is also a great compost activator and will give you a faster turnaround on your black gold.
- You can make comfrey tea from bocking 14 plants. Simply put the leaves into a hessian sack or pair of tights. Then you will need a 100 litre water butt with a lid! The leaves are going to decompose and you do not want them to block up the tap, so that is why we need them in a sack. I would say you need roughly 5-6 kilograms of chopped leaves for a 100 litre butt. After two – three hot weeks in the sun you are ready to check on your comfrey tea. Hold your nose when you do this as it will be very strong in smell and really put you off, but the stronger the smell the better! Use diluted as a foliar spray in the early Summer evenings or to water directly to the base of your plants. Remember not to use early in the morning as the heat of the day may cause scorching to the leaves of your plants.
- This type of comfrey can be used as a mulch. We grow a lot of native British herbs and they tend to need a good mulch to retain the moisture as much as anything else. Chop or shred the leaves of your bocking 14 and lay around the base of any plants you wish to help. It will provide those nutrients we spoke about as well as acting as a weed suppressant and moisture retainer and regulator.
- Bocking 14 works well as a green manure. This is simply a process of planting borage or comfrey in an area that does not have much nutritional content left. A slightly overused and tired patch in your garden. We then let it grow and chop it back with a sharp spade, just as it is going over. Wait a few days and then dig through. It will have held back the weeds as well as fixing some new NPK into your soil.
- As a companion plant comfrey or specifically bocking 14 can be planted with tomatoes and many fruit trees. It’s primary use is to attract pollinators to the area as it has a ready supply of nectar. This is where confusion with a herbalists variety would be a possible issue as bocking 14 will not go to seed and spread becoming an invasive ‘weed’ in you garden.
- Wilted comfrey leaves that have been cut back the day before and left in the sun make a great lining to a new planting area. So if you are popping in a new tree, dig your hole a little deeper than needed, line with wilted comfrey leaves and a few tablespoons of Epsom salts for magnesium and then sprinkle with soil. Leaving a hole where the new roots cannot touch the salts or leaves but have room to grow into these areas.
TOP TIP comfrey tea stinks to high heaven’s and it is not advised to have a water butt filled with it too close to your house, or your neighbors house. So think carefully about the positioning of your stinky butt. We also have curious kids, so we keep the lid weighted to stop anyone trying to accidentally splash their sister with it! It will stain clothes as well as making you smell so bad! You will need to still be careful even when using in a watering can not to splash yourself. Foliar spray when there is little wind to carry it on to you as well!!!
Is Comfrey Poisonous
Comfrey has been banned in the US due to it’s chemical make up of pyrrolizidine alkaloids. These alkaloids are linked to severe liver damage, some cancers and even death when consumed. Therefore oral comfrey has been wildly banned as poisonous.
The use of comfrey in topical treatments has a body of research to show it’s benefits. When we say a topical treatment we are referring to one applied directly to the skin. Comfrey is linked to anti-inflammatory and analgesic effects, but more prominently to skin regeneration. This has led to it being used as a natural wrinkle remover in a face balm.
Besides being used as an anti wrinkle cream, comfrey is relatively well researched as an active ingredient in wound healing, myalgia and ankle joint treatments. Used as a cream or balm rather than taken orally and ingested.
Why Do Herbalists Grow Comfrey
The comfrey that is grown for medicinal uses is the common comfrey. It is grown to be harvested and used in balms and salves for topical use. IN NO WAY IS IT GROWN TO BE EATEN. The botanical name is Symphytum officinale and it is commonly known as comfrey, common comfrey, true comfrey, boneset, knitbone, knitback, comfrey consound. These names come from it’s long tradition in herbal medicines of Europe and Asia.
You can make a basic salve from your own comfrey using beeswax and Ashley from Practical Self-Reliance has a fantastic recipe, available here.
It is important to note that any medical treatment you embark on should be after consultation with a qualified medical professional. I am a keen amateur herbalist and in no way should my research be taken in place of your own under consultation with a qualified professional. Whilst a homemade salve is great, it is always worth looking at purchasing one with a recommended dosage level. This way you are adhering to all of that fabulous research that surrounds comfrey.
Where To Buy Comfrey In The UK
You can purchase from reputable online nurseries and we recommend 9cm plants like, comfrey bocking 14 plants. Always choose a reputable nursery who will send you the plants in season! Once purchased you can easily propagate following our methods above. To my mind this makes comfrey a once in a lifetime investment with a free crop for life, if treated correctly.
In the UK you can purchase symphytum officinale seeds online here, they will need full stratification as described in our guide.
We do make a lot of salves ourselves, however it is well worth purchasing from professionals who are able to get the accurate dose when it comes to medicinal herbs. Comfrey has a recommended concentration for optimum results and this is ensured when you buy through a reputable company.
- Mugwort – How To Grow And Use
- Yarrow (Achillea millefolium) – A Grower’s Guide To Success
- Borage – How To Sow, Grow And Harvest
- How To Apply Zero Waste Principles In Your Garden
- Green Manure – What, Why and How!
- How To Grow Angelica In The UK
- The Best Mulch To Use In Your Garden
We hope to have inspired you to grow some of your own comfrey. It is a renewable fertilizer and as long as you can keep it under control it will reward you year on year. Comfrey tea is probably akin to being dipped into the bog of eternal stench, so be careful when using it to water your plants!
Just remember not to use as an internal medicine and if you are suffering to seek correct medical treatment before embarking on any herbal route. There is a lot to love with comfrey from the beautiful flowers to the wonderful benefits to your garden, so what’s stopping you getting some started today?