I thought I would descibe my method for making a kick-ass organic fert from Russian comfrey, my plants love it. I have read other techniques, but this works well for me.
First you need to obtain some roots of Russian comfrey, Bocking 14 is the variety you need, a google search will score you some. They cost about a pound a root. Plant them according to the supplier´s instructions, I find they prefer a shady spot, if you have one where water collects that is best of all. Russian comfrey is a perennial plant that dies back and becomes dormant in winter with leaves reappearing in the spring. Here is my comfrey bed.

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Fill a large mineral water container (or similar) half full of water, pull off handfuls of leaves and stuff them into the container until it is full. As shown. You can strip the comfrey plants 3 or 4 times in a summer season.

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Every day give the container a shake, and release the cap a little to let the gases that have formed escape - they smell like a fart to be proud of. After a fortnight top up the container with fresh leaves and continue the shaking, etc. procedure. After a further fortnight - four weeks in all - your fert is ready. You will have an incredibly smelly, dark brown mix of liquid and plant solids.

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Strain off the solids - you can add them to compost, they make a good activator, dig into your comfrey bed or MJ soil mix, use as a mulch.
The liquid is your final product, dilute 20:1 with water, feed often.
The liquid contains NPK, especially good levels of K. I use it alternately with BioCanna crecimiento and floracion as appropriate.
Of course, you can´t take NPK out of your soil for ever without putting some back in. I fert my comfrey bed with a cheap 4-6-8 chemical fert, which my plants make into organic fert. And the comfrey plants do respond very well to being ferted.

Cheers Fella! Always good to know these things!

Some one new down the allotments has done a they had a nice patch of comfrey and the muppet has just took a rotavator to it just told them its a root propagator that patch is going to be fecking huge or extremley hard work for him to keep clear now...

Hi Canthis i grew some comfrey this year not Bocking 14.How would you advise storing it for over the winter months?.Making the fert and just keeping it in bottles OR drying/freezing the leaves and making it up as required through the winter?

Jimboo, I make the fert and store it in my shed. Seems to keep OK and I have some nice organic fert for the spring.

my garden is over-run with what appears to be comfrey...hairy leaves ect....

i might just have to make a big batch.
lucky i read this cos i was gonna weedkill the lot next weekend...that would have ruined my free nute supply.

a few questions 4 ya
how long does it stay viable in the bottle? does it have a shelf life?

Cheers mate i will just do the same

Hi folks, do you know how long you can keep it for once it's bottled and how many ml per litre do you use
on ganja in early flowering? (sativas)

Cheers

Its a shame that i wasn't growing in soil myself .....

The Old Man has been making this in an old dustbin in his garden for the last 40 odd years

Its to late to make any this year any leaves left will be stripping nutrients back to the roots for winter.

This is the best guide on making neat comfrey extract, neat extract is used ten to one for heavy feeders like tomatoes and cannabis.

In reality the extract as shown in this topic ie water extract is so weak that, if diluted twenty to one would be less than homeopathic in effect.

Cheers OT, got buckets full made this summer
been wondering for ages what the correct dosage is.

hello, nice thread....... one thing i would do different to what your doing is to mulch the comfrey sludge around the growing comfrey, rather than feeding them chemical salt. That way you comfrey will be happier and more nutritious! and save yourself money on chem fert.