Vegetable Garden

How to Make Comfrey and Stinging Nettle Fertilizers

April 30, 2012
How to make comfrey or nettle fertiliser

Comfrey Plant


Used for centuries before chemical fertilizers became popular, homemade comfrey or nettle ‘teas’ are easy, quick-release fertilizers that you can easily make at home and will save you money as you avoid buying artificially created variations.

When to use fertilizers

If you keep the soil fertile by adding lots of bulky organic matter (well-rotted manure, compost, leaf-mold) you shouldn’t have to worry about adding additional fertilizers too much.  However, there are certain circumstances when it’s helpful:

  • To raise nutrient levels in a poor or new soil.
  • To get higher yields from hungry crops such as potatoes, cabbages & squashes.
  • In containers where the nutrients in compost are used up quickly.
  • Top dressings of fertilizer can be added once the plants have established.
  • As an instant plant ‘pick-me-up’ sprayed on as foliar feeds.

Comfrey ‘Tea’

Rich in potash (potassium or K – great for flowering), comfrey also contains high levels of Nitrogen (N) for leaves (N3:P0:K10).  The variety Bocking 14 is the best one to plant in a garden as it’s less invasive. Comfrey can be difficult to get hold of in Ireland and is usually obtained by asking fellow gardeners, though you may find it in local markets (I’ve been reliably informed there’s a market stall in Kilkenny Farmers Market that often sells it). The Organic Centre sometimes stock root cuttings and in the UK it’s available online from The Organic Gardening Catalogue.

Wilted comfrey leaves can be placed around plants as a mulch or used as a liner in potato and tomato trenches – make a trench, add the leaves, cover with a sprinkling of compost then plant on tip of them. They can also be added to compost heaps (but only in small batches as they can go slimy). Be careful not to add any roots or flower heads or you may have comfrey popping up where you don’t want it.

A rich comfrey brew is made by packing leaves into an old dustbin, about half way up, then placing a board on top, weighed down and a lid added. A hole can be drilled in the bottom of the bin and a jar placed under to catch the drips or a tap added. The resulting liquid should be diluted 10 – 20 times with water before use.  Avoid getting it on your skin. Alternatively infuse around 3kg of fresh comfrey leaves with 45 litres of water and leave to stand for a month. This tea can be added undiluted to containers or plants for a pick me up.

How to make comfrey or nettle fertiliserStinging Nettle ‘Tea’

Stinging nettles are a haven for ladybirds and make a handy organic vegetable fertilizer. They are lower in potassium than comfrey but much easier to come by and contain an average N2:P0:K5 but with high trace elements. Young stinging nettle leaves are cut in the spring (wearing a thick pair of gloves!) and made the same way as comfrey tea. A quick method is to add 1kg of nettles to 20 litres of water.  Use the liquid undiluted when it starts to smell, usually a couple of weeks.

Alternatively, organic gardening guru Joy Larkcom recommends wrapping some nettles up in a sheet of muslin or old net curtain, then tying and hanging them in your water-butt.  Change the bag often as the leaves break down so that the feed doesn’t become too strong.

Have you used homemade fertilizers in your garden? How did you find them?



  • Reply susan April 30, 2012 at 8:15 pm

    I have made the nettle tea, lovely and smelly now, can you please explain how to dilute (10-20? ?) how often to use and if they can/should be used on young cabbage and tomatoe plants please, thank you for any advise 🙂

    • Reply greensideupveg April 30, 2012 at 9:52 pm

      If you make the concentrated comfrey brew it should be diluted until it resembles weak tea Susan, usually 10 – 20 times depending upon how many leaves you’ve used. If you’ve made the nettle tea using half leaves, half water you can use the liquid without diluting it any further and once it starts to smell is a good indication it’s ready! Some gardeners add fertilisers once the fruit starts to swell (in the case of strawberries, tomatoes, beans etc) or in the case of cabbages once the heads start to swell as they benefit from the nitrogen in the nettles, but if you’ve added lots of well rotted manure in the autumn it mightn’t be necessary. If you want to be doubly sure whether fertiliser is really necessary, you could purchase a simple soil analysis kit and check (full instructions on how to use the kits are usually printed with them).

      • Reply susan April 30, 2012 at 10:26 pm

        Thank you, really love all your updates and information, great site 🙂

  • Reply Mike May 1, 2012 at 2:32 pm

    Very good information. Last year we worked to establish both nettle and comfrey beds on our property and now I can begin to use them in the manner you suggested.:)

    • Reply greensideupveg May 1, 2012 at 3:37 pm

      That’s good to hear Mike, hopefully it will pay you dividends with this year’s crops.

  • Reply Simon Jennings May 5, 2012 at 11:48 am

    For nettle tea I use only the stems. Nettle leaves are a great edible plant.

    Try Nettle Pesto

    Or nettle soup

    I also find that nettle tea sprayed on brassica’s works well as part of an anti caterpillar program

    • Reply greensideupveg May 5, 2012 at 11:49 am

      Thanks for sharing that Simon. This is definitely going to be the year I cook with nettles!! Great tips 🙂

  • Reply cathsveggies1 February 26, 2013 at 1:41 pm

    I make both the comfrey and the nettle feeds. Sometimes I mix the 2 together. I did not have to buy any from the garden shop last year 🙂

    • Reply greensideupveg February 26, 2013 at 2:02 pm

      ooh, lots of goodness in your garden! I was just trying to add your blog to my reader as it’s playing up. It’s looking busy in your garden already 🙂

      • Reply cathsveggies1 February 26, 2013 at 2:53 pm

        Thank you, can’t wait to get into the full swing again.

        • Reply greensideupveg February 27, 2013 at 7:27 pm

          Me neither. It’s been a long winter I think because so wet and dull this year. Looking forward to some brightness.

  • Reply Nettle tea (feed) May 13, 2013 at 9:10 pm

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  • Reply eoin June 11, 2014 at 11:51 am

    Great post Dee, going to be making some for the allotment next week.

    • Reply greensideupveg June 13, 2014 at 2:11 pm

      Thanks Eoin

      So difficult to fit our own in at times when we’re out and about in other gardens, enjoy the great weather 🙂

  • Reply Richie August 28, 2014 at 5:59 pm

    hiya greensideupveg,
    I have heard that it’s not advisable to use seeded/flowering nettle plants in compost teas, but can’t find out the reason why.

    Can you shed any light on this please 🙂

    • Reply greensideupveg August 28, 2014 at 10:46 pm

      Richie I’m not entirely sure tbh. Perhaps in case the seeds escape into the soil if not stained before they end up in the Tea and subsequently germinate and spread nettles all around. I know we shouldn’t cook with nettles once they’ve flowered as they contain cystoliths that aren’t good for the kidneys but whether that seeps into the soil and causes damage I’m afraid I’m not certain. I’ll ask around 🙂

      • Reply Richie August 29, 2014 at 1:20 pm

        Have checked and cystoliths do seem to bring up (unproven) concerns regarding kidney stones when used in a herbal tea to us to drink.

        But, for a compost teat/ACT then the calcium carbonate (which is what cycstolith’s are) should hopefully be converted into usable calcium which, in my book, along with Magnesium, is one of the micro nutrients that should be considered as Macro nutrients alongside NPK 🙂 as plants use a lot of both to metabolise the other nutes.

        Thanks again,

        • Reply greensideupveg August 30, 2014 at 1:45 pm

          Thank you for checking that out Richie, all sounds good then 🙂

  • Reply 9 Winter Gardening Jobs You Can Do In Your KitchenGreenside Up January 18, 2015 at 12:25 pm

    […] need to replace it. Adding well-rotted organic matter to soil such as animal manures, leaf mould, comfrey and nettle fertilisers, homemade compost or green manures not only helps to add nourishment to soil and increase plant […]

  • Reply Sally Cronin April 1, 2015 at 6:26 pm

    I’ve heard of comfrey, and have read that it is natural to Ireland, etc, but where do I source some seeds? Appreciate your advice, thanks 🙂

    • Reply Dee Sewell April 1, 2015 at 10:51 pm

      You’ll need to get hold of plants Sally is it’s usually propagated from root cuttings or divided. In Ireland you can often find plants at markets or ask around neighbours. The Organic Centre in Leitrim sell them too.

    • Reply cathsveggies1 April 1, 2015 at 11:15 pm

      If I may please give you the place where I bought my comfrey roots from in west Cork..I just found her on Done Deal, but you can send her a message. Her name is Poppy and reliable….

  • Reply Sophie Skinner May 9, 2015 at 12:05 pm

    Very helpful. Thankyou

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  • Reply jane fiori May 31, 2016 at 4:40 pm

    i have made the nettle compost tea and now extremely smelly so assume ready – but I have just read somewhere that I should not have used chlorinated water ( ie tap) and I have used tap — and that it should not be used on roses ( was about to add it). Are both points critical?

    • Reply Dee Sewell May 31, 2016 at 5:00 pm

      Hi Jane, yes smelly is good! I’ve never heard about the chlorinated water, though they could have a point. Anything that fruits and flowers prefers a fertiliser high in potassium which comfrey and nettles both are so that’s another I haven’t heard of. I’ve used it on my own and they’ve been fine. I’ll have a did around and see if I can come up with anything more.

  • Reply Alex Jane April 13, 2017 at 10:39 am

    I was wondering how long the comfrey and nettle teas would keep? Would old tea harm the plants rather than helping?

    • Reply Dee Sewell April 26, 2017 at 3:02 pm

      Hi Alex, I checked with my horticulture tutor at Kildalton and we both feel they should keep for a good while once they’re in an airtight container with a lid tightly screwed on. To be safe, just use on one or two plants before letting loose on them all.

  • Reply Nettle Soup Recipe | Greenside Up May 12, 2019 at 9:17 pm

    […] days when I’m working with groups, I often extol the virtues of homemade fertilisers and provide a nettle tea recipe. During these sessions, older people have regaled us with childhood memories of their mammies using […]

  • Reply Robert January 25, 2020 at 10:38 pm

    Any suggestions for similar plants common in zone 9/10 California? Nettles are very hard to come by here.

  • Reply Yanina Dowling July 8, 2020 at 9:48 pm

    I have just watered my veg garden with a diluted comfrey and nettle mix ..rather smelly!…as i have splashed the plants with the mix.. mainly lettuce and chard, can i harvest them in a day or two to eat and give to my chickens…

    • Reply Dee Sewell July 12, 2020 at 2:07 pm

      They should be fine once you rinse them off. General guidance is to always to try and water the base of the plants and avoid the stems and leaves etc., as the plants can be ‘burnt’ by the fertilisers if they’re strong.

  • Reply KITTY PEARSON June 29, 2022 at 9:12 pm

    I have loads of organic Nettles and Comfrey in Durrow Co. Laois if anyone would like some for free they are more than welcome! 087-9265423. Last year I mixed nettles and comfrey and rain water and left them in a metal drum (which became quite rusty on the inside) when I went to use it a few months later I diluted it right down to very weak tea, like 15 to 1. Unfortunately, none of my flowers in both pots and beds liked it. Any Idea what I did wrong?

    • Reply Dee Sewell February 26, 2023 at 8:39 pm

      Was the water sitting there for a long time? It’s advised to clean out rainwater tubs every year as bacteria can build up.


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