Vegetable Garden

How to Make Comfrey & Nettle Fertiliser

April 30, 2012

Used for centuries before chemical fertilisers became popular, home-made Comfrey or Nettle fertilisers are easy to make and will save you precious coins.

When do you use fertilisers?

If you keep the soil fertile by adding lots of bulky organic matter (well-rotted manure, compost, leaf mould) you shouldn’t have to worry about adding fertilisers.  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 fertiliser 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 and Phosphorous (P) for roots.  The variety Bocking 14 is the best one to plant as a fertiliser 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. 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.

Nettle ‘Tea’

Nettles are high in nitrogen (so great for anything in the cabbage family). Young nettle leaves are cut in the spring (wearing a thick pair of gloves!) and made the same way as Comfrey tea. An easier method is to half fill a bucket with compacted nettles and cover with water.  Use the liquid when it starts to smell.

Alternatively wrap some nettles up in a sheet of muslin or old net curtain, tie and hang in your water-butt.  Change the bag frequently as the leaves break down so that the feed doesn’t become too strong.


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  • 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

    […] here on making nettle tea and comfrey tea How to make Comfrey & Nettle Fertiliser – Greenside Up Nettle tea is particularly high in nitrogen, so good for leafy plants (cabbage, lettuce, […]

  • Reply Growing Vegetables in Containers March 26, 2014 at 3:22 pm

    […] Generally, potting mixture has enough nutrients to last a few months. However if you notice a check in growth, or you’ve planted particularly ‘hungry’ feeders in your containers, liquid seaweed is full of nutrients and trace elements and can be watered into the soil in the containers as can home-made nettle or comfrey feeds. […]

  • 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 […]

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