Comfrey tea, or comfrey fertiliser, is an all-organic, easy to make plant food that provides excellent nutrition, especially for flowering and fruiting plants. As Alys Fowler explains: “Comfrey is rich in potassium (K), which is required for fruit production, and also contains potash (P) and nitrogen (N). A liquid comfrey feed has a higher NPK ratio than farmyard manure.”
Please N.B. comfrey tea is for use on plants only, and is not for drinking. Although comfrey can be used to ease inflammation via topical application in poultices or lotions, the plant is toxic if ingested and could seriously damage your liver.
Comfrey (Symphytum spp.) is a quick-growing deciduous perennial. The recommended variety to grow for tea production is Bocking 14, which is sterile and so not invasively self-seeding (although it will re-grow quite happily from even a tiny bit of root), but if you already have common comfrey on your plot it’ll work just as well and give you a good reason not to weed it out (as if comfrey being an amazingly bee-friendly nectar source wasn’t reason enough).
1. Harvest Your Comfrey
Comfrey dies back in autumn and begins to re-emerge round about the start of April. By mid-May it’s probably looking like this:
Opinions differ as to whether or not to chop the entire plant off a couple of inches above ground (the fastest method) or to cut individual leaves. I prefer the latter, taking the largest leaves and leaving around a third of the smaller leaves to aid re-growth. I also leave any flowers or flower buds on the plant – bees love ’em – but you can remove the flowers to make more energy available for leaf production if you prefer.
2. Tear, Crush, Pack in a Pot
All good tea needs a good teapot, in this case consisting of an inner and an outer container. For the inner, I use a bog-standard terracotta plant pot with a single hole at the bottom, and for the outer a plastic plant pot without any drainage holes. The terracotta pot should fit inside the plastic pot snugly, ideally with at least a couple of inches of clearance underneath.
Crush, tear or otherwise bruise the comfrey leaves and pack them tight into the pot, filling it right up to the brim if you have enough leaves.
Some comfrey tea recipes will tell you to add water at this stage, but that method will result in an almighty stink as the plethora of bacteria and microorganisms in the water get to work on digesting the comfrey and fart out all sorts of waste gases.
For less stink and a more concentrated end product, do not add water. The leaves will rot down quite happily with the help of the bacteria and microrganisms already living on them, the yeasts in the air etc., (which for some reason are a lot less, er… farty. And yes, that was the science bit…)
3. Put a Lid On It
The lid needs to be big enough to cover the pot and keep out the rain (no water, remember?) and heavy enough that it won’t be blown away in the wind. I use a small concrete paving slab, but a plastic lid weighted down with a brick will do just as well.
4. Leave it Alone
The tea brewing process takes around 8 – 12 weeks, largely depending on the weather (the warmer, the quicker). You’ll know it’s done if you take a sneaky peak under the lid and see that the comfrey leaves have all-but disappeared (any plant matter remaining in the inner pot can be added straight to your compost heap) and the bottom of the outer container will be sloshing with lovely, thick, brown-black, concentrated comfrey tea, which you can drain off and store for when you’re ready to use it on your plants.
The volume of liquid you end up with will obviously depend on the volume of leaves and size of container you brew in. The pot I use makes about a quarter litre, which isn’t a huge amount, but I’m gradually expanding my production capabilities by adding more comfrey plants to a row beside the compost bins, as and when I find the seedlings growing elsewhere on the plot.
5. Slosh it Around
To use your comfrey tea, you’ll need to dilute it to approximately 1-in-20. So for a standard 10-litre watering can, that’s about half a litre of concentrate. You can then use the feed on your fruit bushes, fruit trees, courgettes, squashes, tomatoes, cucumbers etc. to aid with fruit set and development, or on your flowering plants to boost their blooms.
For a more nitrogen-rich feed to use on your leafy veg, you can make nettle tea via the same method. (I confess I’ve had mixed results with nettle tea in the past – I didn’t seem to get anywhere near as much end-product for the same volume of leaves – but I’m trying again this year, so we’ll see what happens.)
How about you? Are you a fan of comfrey tea? Do brew it up by a different method, or can you suggest an improvement or refinement to the above? Let me know, via the comments…