How to Make Comfrey & Nettle Fertiliser

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.


20 thoughts on “How to Make Comfrey & Nettle Fertiliser

  1. 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 :)

    • 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).

  2. 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.:)

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  5. 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 :)

    • 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 :)

      • 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,

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