Comfrey liquid fertiliser

24 November 2021
This photo of our comfrey clump was taken a couple of days ago.

Comfrey is one of the easiest herbs to grow and is also one of the most helpful herbs in the garden.  If you have a chance, particularly if someone offers you a comfrey root cutting, take it and grow your own clump. You won't have to buy fertiliser again.  

Comfrey sends down a tap root and that mines the soil for minerals and makes them available in the leaves. Using those leaves in a fertiliser will give you minerals such as Vitamins A, B1, B2, B3, B5, B6, B9, B12, C and E, as well as boron, calcium, chromium, cobalt, copper, iodine, iron, magnesium, manganese, nitrogen, phosphorous, potassium, selenium, sodium and zinc. And comfrey nutrients are immediately available to your plants, unlike pellets and granules, blood and bone etc which have to break down for a a couple of weeks before they become available to the plants.

But that's not the only reason to grow comfrey. I use it here to mulch tomatoes and potatoes when I plant them.  I scrunch up the leaves to begin the breakdown of the leaves and over the following week, when I water the plants, the comfrey mulch will start fertilising your plants as well as add organic matter to the soil. Comfrey is an excellent source of nitrogen, potash, phosphorus (NPK) and calcium so if you're growing green leaves such as lettuces, silverbeet or cabbages, comfrey will help you grow magnificent vegetables.  Are you growing flowering fruits and vegetables?  Then comfrey is your go-to fertilising liquid - tomatoes, potatoes, egg plant, any of the melons, stone fruit, citrus trees, passionfruit, beans, peas, chillies, capsicum/peppers, herbs and a whole lot more.

Someone might tell you that comfrey spreads and you have to be careful, but that's not quite right. It doesn't spread out like bamboo does but if you plant comfrey in a hole, it will slowly increase the clump but it will take many years before it outgrows it's spot. Comfrey likes water but we've been in drought here for the past ten years and our comfrey is still growing strongly. Make sure the space you choose is where you want it to grow for a long time because if you try to dig it out later, leaving only the slightest piece of root behind will make it grow again. The best spot is either at the edge of your garden or near the compost heap because it won't get in the way of your regular plantings and if you have an excess of comfrey leaves, you can throw them onto the compost heap and they will accelerate  decomposition and add nutrients to the heap. 


  • Cut the leaves from the comfrey plant and put them into a bucket that has a lid. Half fill the bucket with leaves and put a brick on top of them to stop them floating. Fill the bucket with water and put the lid on.
  • It will smell ... a lot. 
  • Stir it every couple of days and in two or three weeks you'll have a dark brown liquid that is an excellent feed for your plants. 
  • When the comfrey fertiliser is ready, strain the leaves out of the mixture and put them in the compost - it will help your compost decompose faster. 
  • The ratio to use is one part comfrey concentrate to 10 parts water. It will make up a liquid that looks like black tea. If you make a weaker mix you can use it more frequently.
  • It's equally effective poured over leaves and around the root ball on a weekly basis.
  • If you have an excess of comfrey liquid, store it in plastic milk bottles in a dark place.


When you want to give root cuttings to your family and friends, and I encourage you to do that - the less chemical fertilisers in the world, the better - choose a spot at the edge of the clump and with a spade, dig into the clump as far down as you can go.  Hopefully, when you pull the spade back you'll hear a "snap" and you can pull up the cutting with your spade and hand.

There are about 30 species of comfrey and  they grow in zones 4 - 9.  It will produce leaves all year but start to die down in winter. Depending on your climate, the leaves will die back completely and over a couple of weeks, with watering, will regrow when the weather starts to heat up.  During that regrowth, it will form white, pink or mauve insignificant, bell-shaped flowers.


  1. Thank you for this. I’ve used the comfrey leaves but didn’t know about making liquid fertiliser. I’ll be doing this from now on.

  2. I've grown and used comfrey for many years. I bound up my dads broken ribs with comfrey poultices when he was 89. Held them on him with gladwrap. After a few days, I slathered him in home made comfrey balm instead. Drs told me his healing would take months. His bones were so badly broken. He was driving again in 3 weeks!

    I dry the leaves and infuse extra virgin olive oil with the dried leaves along with vitamin e and bees wax to make the balm. You can use the dried leaves to sprinkle their powder into the soil when you are planting seedlings. Easy way to give them what they need. Comfrey tea is also amazing. Large handfuls of leaves as mulch under plants- brilliant.

    I was always taught to use the biggest leaves, before they flower. If you see flowers starting, pluck them out, unless you specifically want them to attract pollinators. Great article, well researched. Xx

    1. Amazing result! I remember when it was a big news story not to eat the plant due to its alkaloids which now my cynics mind thinks was it because it's actually marvellous on more than the 'knit bone ' level and farmers who used it in the feed mixes never reported problems only benefits.
      Thanks for a great article about one of my favourite garden fertilisers, Rhonda, and my best wishes to you <3

  3. Your comfrey plant looks amazing! I will see if I can find it here in California. I love the flowers, too. They are bell shaped. I feed my plants compost tea, which also really is effective. Would love to try your method, as well.

  4. And the bees love the flowers! Win, win!



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