Comfrey tea in UK greenhouse

[DarrenC]

I was wondering if anyone has tried just using comfrey tea as fertiliser and what sort of results they got.

It's my first season growing anything and decided to try just using comfrey tea after seeing it on BBC's Beechgrove Garden programme - it also helps that there's a few good patches of it nearby

The only thing I've learned so far is that it stinks and I need to wear gloves whilst making/using it because the smell doesn't leave my skin no matter how many times I wash up

[MendozaMark]

Hi Darren,

Sadly there is no greater benefit to using comfrey in any form then any other plant. It is not superior in NPK, trace elements or anything else we seek. I grew and still have 3 comfrey plants that i planned on using as a fertilizer. I even made 2 batches of stinky tea. I did use the tea and anecdotally, didn't see any difference. Just recently, I put the question of comfrey use to the Garden Professors, a highly qualified authority in the world of Horticulture. They said i was wasting my time basically.

Here is a link to the discussion on facebook.

https://www.facebook.com/groups/Gard...4113272051490/

Cheers Mark

[zipcode]

UK sure loves comfrey tea. I see it on uk forums all the time. I've wondered where they get it from, over here it's a pretty rare plant.

[DarrenC]

Thanks for the replies.... I will have to do more reading, obviously

It's quite a common plant near my home, I have 4 plants in my garden as well and most allotments have a patch of it...

We seem to be coming to the end of our summer here, the night time temps are getting dangerously low (4*C last night) I've been using comfrey tea all year, with no other fertiliser - I have nothing to compare it to but my plants seemed to have done ok. Next year I will try a comparison and grow 3 plants, unfertilised, comfrey and a normal chemical fertiliser (if I can find the space in my greenhouse)

I would say that I'm not dismissing the advice but there's a gardening programme on TV here called Beechgrove Garden and they did exactly that comparison last year and the comfrey plant was the most productive. This also might explain why it's all over UK gardening forums

[MendozaMark]

Originally Posted by DarrenC

Thanks for the replies.... I will have to do more reading, obviously

It's quite a common plant near my home, I have 4 plants in my garden as well and most allotments have a patch of it...

We seem to be coming to the end of our summer here, the night time temps are getting dangerously low (4*C last night) I've been using comfrey tea all year, with no other fertiliser - I have nothing to compare it to but my plants seemed to have done ok. Next year I will try a comparison and grow 3 plants, unfertilised, comfrey and a normal chemical fertiliser (if I can find the space in my greenhouse)

I would say that I'm not dismissing the advice but there's a gardening programme on TV here called Beechgrove Garden and they did exactly that comparison last year and the comfrey plant was the most productive. This also might explain why it's all over UK gardening forums

Please keep us informed on your experiment. I still have lots of tea made so I may do the same on a couple of plants. How are you incorporating it into your watering/feeding regiment ? I was diluting it with water at 1 part tea/20 water ratio, and using it about every 2 weeks mid season on. I couldn't start any earlier because i was starting the comfrey from seed. Also it was just for container growing of tomatoes and peppers.

I got inspired from reading about a master hot pepper grower in the UK using it. So I will blame you Uk'ers if it doesn't work !

Cheers,

Mark

[bower]

Sometimes I forget that gardening is a bit of a competitive sport. Especially when it comes to the best fertilizer, or 'organic' vs 'conventional/chemical' methods... the more competitive sorts do love to trash what others do, whether they have evidence or not.

I remember reading that comfrey was high in potassium in my (very old) copy of the Encyclopedia of Organic Gardening. Just googled and, at the least, this article by Rodale cites some actual analytic test results of what actually is in comfrey.
http://www.rodalesorganiclife.com/garden/comfrey-power

"Researchers in British Columbia analyzed the NPK (nitrogen, phosphorus, and potassium) ratio of comfrey leaves by air-drying them and analyzing the powdered leaf tissues. They found that the leaves have an impressive proportion of 1.8-0.5-5.3. To compare, kelp meal has an NPK ratio of 1.0-0.5-2.5, and homemade compost ranges from 0.5-0.5-0.5 to 4-4-4 (depending on what ingredients you use). Comfrey is also rich in calcium and many other valuable plant nutrients it mines from deep in the subsoil."

I've been using crushed kelp as a source of potassium, but I got a reminder this year, that kelp won't break down quickly at all in cold soil, and left the plants deficient in the bad weather. I'd be better off using comfrey, since it should break down much more easily. I still have some comfrey in the garden in spite of my efforts to remove it a few years ago. Guess I should take care of it and make a thriving patch... I guess you'd need quite a lot to make up by weight the amount of kelp I drag home from the beach every year. Why do I never find the usefulness of something unless I threw it away.

[MendozaMark]

Originally Posted by bower

Sometimes I forget that gardening is a bit of a competitive sport. Especially when it comes to the best fertilizer, or 'organic' vs 'conventional/chemical' methods... the more competitive sorts do love to trash what others do, whether they have evidence or not.

I remember reading that comfrey was high in potassium in my (very old) copy of the Encyclopedia of Organic Gardening. Just googled and, at the least, this article by Rodale cites some actual analytic test results of what actually is in comfrey.
http://www.rodalesorganiclife.com/garden/comfrey-power

"Researchers in British Columbia analyzed the NPK (nitrogen, phosphorus, and potassium) ratio of comfrey leaves by air-drying them and analyzing the powdered leaf tissues. They found that the leaves have an impressive proportion of 1.8-0.5-5.3. To compare, kelp meal has an NPK ratio of 1.0-0.5-2.5, and homemade compost ranges from 0.5-0.5-0.5 to 4-4-4 (depending on what ingredients you use). Comfrey is also rich in calcium and many other valuable plant nutrients it mines from deep in the subsoil."

I've been using crushed kelp as a source of potassium, but I got a reminder this year, that kelp won't break down quickly at all in cold soil, and left the plants deficient in the bad weather. I'd be better off using comfrey, since it should break down much more easily. I still have some comfrey in the garden in spite of my efforts to remove it a few years ago. Guess I should take care of it and make a thriving patch... I guess you'd need quite a lot to make up by weight the amount of kelp I drag home from the beach every year. Why do I never find the usefulness of something unless I threw it away.

I read that info before and that is why i started the comfrey after i was inspired by the UK pepper grower. Unfortunately, the data/research isn't supported by the scientific community. When i have more time I will try to go through the garden Professors threads to see exactly why. I would love to see comfrey prove its worth in the garden as I put a lot of effort into getting the seed here. Like I said earlier, i will trial it out better this year.

I have only used Kelp meal once , threw a few cheap bags on my neglected lawn back in Moncton, NB. You could see where i ran out in terms of lushness and health. I also really liked marine compost, except if the shells were not composted enough. Cut my hand a few times with one batch. No kelp meal or marine compost here in Mendoza .

Could you use the kelp as a top dressing instead ? Maybe it would benefit you in the long run but not cause any deficiencies in the short run. Or just compost the heck of it for a few years before you use it. Free kelp would be hard to turn down.

Cheers,

Mark

[bower]

Originally Posted by MendozaMark

I read that info before and that is why i started the comfrey after i was inspired by the UK pepper grower. Unfortunately, the data/research isn't supported by the scientific community. When i have more time I will try to go through the garden Professors threads to see exactly why. I would love to see comfrey prove its worth in the garden as I put a lot of effort into getting the seed here. Like I said earlier, i will trial it out better this year.

I have only used Kelp meal once , threw a few cheap bags on my neglected lawn back in Moncton, NB. You could see where i ran out in terms of lushness and health. I also really liked marine compost, except if the shells were not composted enough. Cut my hand a few times with one batch. No kelp meal or marine compost here in Mendoza .

Could you use the kelp as a top dressing instead ? Maybe it would benefit you in the long run but not cause any deficiencies in the short run. Or just compost the heck of it for a few years before you use it. Free kelp would be hard to turn down.

Cheers,

Mark

Heh, no fear of me not using the kelp, six ways from Sunday. I love the stuff and as you rightly said it's free.. and a great excuse to go to the beach. I do use it in compost, and it makes the best mulch for my garlic.. no weeds and whatever breaks down they seem to love it. I also let some kelp rot down for a year in a bag, from time to time, after which it is stored as a powder, more or less water soluble goodies for various TLC purposes.

About the 'professors', are you sure they're not turning up their noses on principle and without good reasons? It wouldn't be the first time that I heard scientists scoff just because they heard some other authority say so, and took it on 'authority' alone and/or out of context, without basing their claim on any actual data.
My best guess is that 'comfrey tea' in the recommended dilution etc was not found to have an amount of nutrients equivalent to some other liquid fertilizer ie strong enough to have effects. Just as the 'kelp extracts' which are sold for mucho dinero are used so dilute that they have only a hormonal effect but no significant or measurable nutrient contribution. That doesn't mean there's no potassium value in bulk raw kelp, obviously.

I think a dry comfrey leaf probably doesn't weigh much and it would take a lot of em to make a pound of 'comfrey ferts', with the label value of NPK that was found in that legitimate study, quoted by Rodale. Weak tea is a whole other matter, of course it won't have the same value if it's mostly water. I think I'd be tempted to try the other method described in the Rodale article, just weighting down the raw leaves and letting the rotted liquid drain into a bucket below, then bottle and dilute for use as we do with eg fish emulsion to keep from burning the plants. The liquid product before dilution should have a nutrient value close to or equal the measured value for dried leaves in the study.... and it's not bad, it's certainly comparable to the values listed on my fish e bottle or my dry chicken manure stuff. Which are not free, like a heap of otherwise useless comfrey would be free. For the labour of making it.

If the actually measured NPK value of raw comfrey material is disputed by the 'professors' on scientific grounds, I'd be interested to hear about that. I haven't seen or reviewed the methods used in the cited study, I'm taking on faith that the science was properly done.

[MendozaMark]

Originally Posted by bower

Heh, no fear of me not using the kelp, six ways from Sunday. I love the stuff and as you rightly said it's free.. and a great excuse to go to the beach. I do use it in compost, and it makes the best mulch for my garlic.. no weeds and whatever breaks down they seem to love it. I also let some kelp rot down for a year in a bag, from time to time, after which it is stored as a powder, more or less water soluble goodies for various TLC purposes.

About the 'professors', are you sure they're not turning up their noses on principle and without good reasons? It wouldn't be the first time that I heard scientists scoff just because they heard some other authority say so, and took it on 'authority' alone and/or out of context, without basing their claim on any actual data.
My best guess is that 'comfrey tea' in the recommended dilution etc was not found to have an amount of nutrients equivalent to some other liquid fertilizer ie strong enough to have effects. Just as the 'kelp extracts' which are sold for mucho dinero are used so dilute that they have only a hormonal effect but no significant or measurable nutrient contribution. That doesn't mean there's no potassium value in bulk raw kelp, obviously.

I think a dry comfrey leaf probably doesn't weigh much and it would take a lot of em to make a pound of 'comfrey ferts', with the label value of NPK that was found in that legitimate study, quoted by Rodale. Weak tea is a whole other matter, of course it won't have the same value if it's mostly water. I think I'd be tempted to try the other method described in the Rodale article, just weighting down the raw leaves and letting the rotted liquid drain into a bucket below, then bottle and dilute for use as we do with eg fish emulsion to keep from burning the plants. The liquid product before dilution should have a nutrient value close to or equal the measured value for dried leaves in the study.... and it's not bad, it's certainly comparable to the values listed on my fish e bottle or my dry chicken manure stuff. Which are not free, like a heap of otherwise useless comfrey would be free. For the labour of making it.

If the actually measured NPK value of raw comfrey material is disputed by the 'professors' on scientific grounds, I'd be interested to hear about that. I haven't seen or reviewed the methods used in the cited study, I'm taking on faith that the science was properly done.

I really don't think so in terms of the garden professors. Their golden rule is you need peer reviewed scientific proof on any subject. That being said if research is incomplete or lacking they say so. Recently i was asking them about using Caliente 199 Mustard as I Bio-fumigant to kill off harmful nematodes. Dr. Linda Chalk-Walker responded she didn't know off hand, then looked into it. She found 6 research papers, 2 of which that didn't find any support for the bio-fumigation. Based on what she found, she said there isn't enough data or research to say yes or no. She did say that wild radishes looked more promising in the bio-fumigation for nematodes. When I asked about the comfrey, I go a ton of no responses and links to research and previous threads about comfrey. It was so overwhelming that i didn't have the time to explore them properly. Lastly, although the garden professors are all about the scientific facts, they do practise as many sustainable organic methods as possible that have been scientifically proven. Its a great free resource and although they sometimes give answers I do not want to hear, I do respect that they are given unbiased.

Just to clarify about their answer to comfrey, it isn't useless. It just is not any better then any other plant. If you have ever made the tea, you know there is some personal benefit to not having to ever make it again. I call it liquid bum.

[DarrenC]

Originally Posted by MendozaMark

Please keep us informed on your experiment. I still have lots of tea made so I may do the same on a couple of plants. How are you incorporating it into your watering/feeding regiment ? I was diluting it with water at 1 part tea/20 water ratio, and using it about every 2 weeks mid season on. I couldn't start any earlier because i was starting the comfrey from seed. Also it was just for container growing of tomatoes and peppers.

I got inspired from reading about a master hot pepper grower in the UK using it. So I will blame you Uk'ers if it doesn't work !

Cheers,

Mark

Background...
I got a 20l bucket with lid, cut the comfrey and left it for a day to wilt then squeezed as much as possible into the bucket, topped with water and then sealed it up in my greenhouse for 4 weeks. From that point on I wear rubber gloves and old clothes whenever I used it.

It gave me a dirty water look stuff that I diluted 1:10 or thereabouts with water I used this once a week
I've grown all my plants in 13l (about 4 gallon US) containers - because thats what I had...
I started feeding them 6 weeks after their final potting on
The only problems I've had are the weather has been terrible and all my San Marzano's got BER - apart from that I think it's worked for me, just don't know if it'd be better or worse without it - but I have a real phobia of eating stuff chemically treated/fed which is one of the main reasons I started growing anything
I've had quite a lot of cherry toms and a fair few big toms, the biggest a beefmaster at 850g or 1lb 13oz.... Tasty 😁

[bower]

Originally Posted by MendozaMark

I really don't think so in terms of the garden professors. Their golden rule is you need peer reviewed scientific proof on any subject. That being said if research is incomplete or lacking they say so. Recently i was asking them about using Caliente 199 Mustard as I Bio-fumigant to kill off harmful nematodes. Dr. Linda Chalk-Walker responded she didn't know off hand, then looked into it. She found 6 research papers, 2 of which that didn't find any support for the bio-fumigation. Based on what she found, she said there isn't enough data or research to say yes or no. She did say that wild radishes looked more promising in the bio-fumigation for nematodes. When I asked about the comfrey, I go a ton of no responses and links to research and previous threads about comfrey. It was so overwhelming that i didn't have the time to explore them properly. Lastly, although the garden professors are all about the scientific facts, they do practise as many sustainable organic methods as possible that have been scientifically proven. Its a great free resource and although they sometimes give answers I do not want to hear, I do respect that they are given unbiased.

Just to clarify about their answer to comfrey, it isn't useless. It just is not any better then any other plant. If you have ever made the tea, you know there is some personal benefit to not having to ever make it again. I call it liquid bum.

Well... I looked up a recipe for 'comfrey tea' and it's just 20 day anaerobic rotting under water... I've never made it but I can tell you that 'any other plant' rotted the same way smells just as sweet. I know it because buckets of weeds, or kelp, plus rain, plus neglect... whew.

I'm sorry though, I have to take issue with the evaluation that comfrey "is not any better than any other plant". That would lead a person to believe that all plants have the same NPK values and therefore have identical fertilizer value... and this isn't true.
Take a look at this database, the NPK of everything (well... not by a long shot, but a start )
https://www.thenutrientcompany.com/n...able-database/
For example of ordinary leafy plant material, nettles and comfrey are listed next to each other (in the 100 items list) and have unique values for NPK. There's more N in nettles and more K in comfrey. I know my friends used to fill a barrel with water in the spring and toss nettles in there, which they used to water the crops. Maybe nettles were better than comfrey for that application because of the higher N. Maybe comfrey is touted for tomatoes because K is important for fruit quality. Maybe comfrey tea is better in the UK because the soil leans toward K deficiency. Maybe some other plant entirely would serve you better in the Argentina pampas.

What I'm getting at, is that saying that comfrey is no better than any other, is like saying that all fertilizers regardless of their NPK are no better than others. That doesn't sound like science to me. Doesn't even sound like gardeners, who do argue mightily about which fertilizer formula is the best!!
Is it conceivably possible that the rotting process in 'tea' making could reduce every plant material to the ho-hum balanced 4-4-4 or similar value usually given for "garden compost" ? I'm not sure why or how that could be, if a single plant material with specific NPK ratio is exclusively used. Losses due to aromatic volatiles? You'd expect different 'teas' to smell different, in that case.
Incidentally, blackstrap molasses has been recommended as another source of K and trace minerals for liquid ferts. I use it to balance the N-heavy fish emulsion. And guess what... it smells pretty good, compared to plain fish.

[MendozaMark]

Originally Posted by bower

Well... I looked up a recipe for 'comfrey tea' and it's just 20 day anaerobic rotting under water... I've never made it but I can tell you that 'any other plant' rotted the same way smells just as sweet. I know it because buckets of weeds, or kelp, plus rain, plus neglect... whew.

I'm sorry though, I have to take issue with the evaluation that comfrey "is not any better than any other plant". That would lead a person to believe that all plants have the same NPK values and therefore have identical fertilizer value... and this isn't true.
Take a look at this database, the NPK of everything (well... not by a long shot, but a start )
https://www.thenutrientcompany.com/n...able-database/
For example of ordinary leafy plant material, nettles and comfrey are listed next to each other (in the 100 items list) and have unique values for NPK. There's more N in nettles and more K in comfrey. I know my friends used to fill a barrel with water in the spring and toss nettles in there, which they used to water the crops. Maybe nettles were better than comfrey for that application because of the higher N. Maybe comfrey is touted for tomatoes because K is important for fruit quality. Maybe comfrey tea is better in the UK because the soil leans toward K deficiency. Maybe some other plant entirely would serve you better in the Argentina pampas.

What I'm getting at, is that saying that comfrey is no better than any other, is like saying that all fertilizers regardless of their NPK are no better than others. That doesn't sound like science to me. Doesn't even sound like gardeners, who do argue mightily about which fertilizer formula is the best!!
Is it conceivably possible that the rotting process in 'tea' making could reduce every plant material to the ho-hum balanced 4-4-4 or similar value usually given for "garden compost" ? I'm not sure why or how that could be, if a single plant material with specific NPK ratio is exclusively used. Losses due to aromatic volatiles? You'd expect different 'teas' to smell different, in that case.
Incidentally, blackstrap molasses has been recommended as another source of K and trace minerals for liquid ferts. I use it to balance the N-heavy fish emulsion. And guess what... it smells pretty good, compared to plain fish.

First off , don't shoot the messenger on this one...lol. I am no scientist, don't have a science degree just a gardener who wants to learn.

The big issue with the report/research on the NPK analysis of comfrey was there were no controls used. He did not grow anything else but comfrey so no comparison could be done to any other plant in that exact soil with exact same inputs. Also if I grew comfrey and you grew comfrey and we had it tested, would it be exactly the same NPK value? No, it would be dependent on the soil and inputs and other variables. Our results would most likely be different then those of the research paper too . So to say any plant has this NPK value really isn't accurate. If you did not use controls by growing different plants in exact same condition then you can't compare the plants in terms of NPK.


That being said, I couldn't find out if proper research was done on comfrey with proper controls. I assumed that research had been done or i would have been told that it was inconclusive due to lack of research, like the mustard question. If I do find something I will post whatever results i find.

Lastly, i have 40 liters of comfrey tea brewed and I will use it regardless. Will I make more, not sure.

Cheers Mark

[MendozaMark]

Originally Posted by MendozaMark

First off , don't shoot the messenger on this one...lol. I am no scientist, don't have a science degree just a gardener who wants to learn.

The big issue with the report/research on the NPK analysis of comfrey was there were no controls used. He did not grow anything else but comfrey so no comparison could be done to any other plant in that exact soil with exact same inputs. Also if I grew comfrey and you grew comfrey and we had it tested, would it be exactly the same NPK value? No, it would be dependent on the soil and inputs and other variables. Our results would most likely be different then those of the research paper too . So to say any plant has this NPK value really isn't accurate. If you did not use controls by growing different plants in exact same condition then you can't compare the plants in terms of NPK.


That being said, I couldn't find out if proper research was done on comfrey with proper controls. I assumed that research had been done or i would have been told that it was inconclusive due to lack of research, like the mustard question. If I do find something I will post whatever results i find.

Lastly, i have 40 liters of comfrey tea brewed and I will use it regardless. Will I make more, not sure.

Cheers Mark

I have switched to worm castings here as i can get a 35Kg bag of bone dry castings for $10 Canadian. I am going to put the rest of my energy into making compost. If i see deficiencies in the plants then will try figure out what my best option is organically. Lastly, if my production is too low then i will plant more or just keep trialling varieties till i find the happy zone.

Cheers Mark

[bower]

Originally Posted by DarrenC

Background...
I got a 20l bucket with lid, cut the comfrey and left it for a day to wilt then squeezed as much as possible into the bucket, topped with water and then sealed it up in my greenhouse for 4 weeks. From that point on I wear rubber gloves and old clothes whenever I used it.

It gave me a dirty water look stuff that I diluted 1:10 or thereabouts with water I used this once a week
I've grown all my plants in 13l (about 4 gallon US) containers - because thats what I had...
I started feeding them 6 weeks after their final potting on
The only problems I've had are the weather has been terrible and all my San Marzano's got BER - apart from that I think it's worked for me, just don't know if it'd be better or worse without it - but I have a real phobia of eating stuff chemically treated/fed which is one of the main reasons I started growing anything
I've had quite a lot of cherry toms and a fair few big toms, the biggest a beefmaster at 850g or 1lb 13oz.... Tasty 😁

Darren, it sounds like you got a great yield for small containers and terrible weather. And no ferts but the comfrey - it's great. You're obviously doing something right - I think regular feeding for plants in containers is the way to go, and maybe weekly is better than every two. I have a tendency to forget when I fed last, until I notice they stopped growing.
I couldn't see the picture. 1 lb 13 oz is huge!

[bower]

Originally Posted by MendozaMark

First off , don't shoot the messenger on this one...lol. I am no scientist, don't have a science degree just a gardener who wants to learn.

No shooting intended.
I do have a science degree, which is why I'm critical... not of you, of 'debunkers' who don't actually pony up any data to support their claims, or misapply scientific concepts/methods to confuse less educated folks. To be fair, I couldn't access the blog because I'm not on facebook and I couldn't find the discussion of comfrey by google. And since Rodale didn't name the researcher I couldn't find the research either. I remain in the dark.

As regards the NPK figures, this type of data on natural materials is never taken as an absolute - they are ballpark figures based upon the available data. This is what we need to estimate how much cottonseed meal or kelp or comfrey to apply as a fert.
From a scientific standpoint "controls" of different plants aren't relevant to this type of data, but the number of data points is important, the more points the better. That means many samples should be tested that grew in different environments, from which an average is taken. It is okay to gripe about someone having only one data point, if that's the case. It isn't sufficient though, to support the claim that comfrey has the same NPK as nettles or hay or some other plant, which according to the available data, are all different.