Comfrey (Symphytum officinale) is a wonder plant. It is a dynamic accumulator, drawing minerals out of the soil and into the roots and leaves, a compost accelerator, a fine ingredient in liquid manure (comfrey tea), beneficial insect attractor, mulch, weed suppressant (we use it as a border around our veg plot to stop the paths getting overrun with weeds, biomass accumulator, livestock forage, human edible (comfrey fritters), a wound healer and it was traditionally called 'knit bone' by herbalists as it helps heals fractures. It's an ideal permaculture plant!
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Comfrey this side of the pond
I dunno about comfrey tea for people. In the US comfrey for internal use is illegal and on foraging walks I give the official UK advice that it should not be eaten. I do steam a portion of leaves once a year and it tastes like "spinach with muscles".
It's great for grazes and is the absolute best thing to rub on nettle stings. Pick a leaf, spit on it, rub it between the palms till it starts breaking up, then rub on the affected area.
The purple comfrey in the video is Symphytum uplandicus (Russian Comfrey), the most common variety in my part of the UK (East London).
Symphytum officinalis is the white comfrey, which herbalists prefer.
If you want comfrey but don't want it seeding all over the place you can get Bocking 14 a variety of Russian Comfrey, which was developed by the Henry Doubleday Research Centre (now Garden Organic). You can divide it every couple of years to get lots of extra plants for yourself and to share with friends.
If like me you have sensitive skin, use gloves to handle the leaves. The hairs irritate my skin.
I use comfrey juice as a super fertilizer. Big bin; put bricks in the bottom; fill thick bag with leaves; stab holes in the bottom of the bag; stand bag on bricks; put weight on top of bag; put lid on bin. Leave for a couple of weeks and you will start getting comfrey juice to decant into bottles.
It smells foul, but is slightly less foul than when soaked in water. Dilute 10 to 1 for spuds or tomatoes; 20 to 1 for everything else.
Internal use of comfrey
It's my understanding that the research that showed comfrey to cause liver damage was in fact done on the extracted pyrrolizidine alkaloids, which by themselves ARE toxic. However, the levels of these alkaloids are much lower in the leaf (particularly those gathered in late summer or autumn) than the root, so I personally don't feel comfrey leaf tea is anything to be concerned about; quite the reverse.
Comfrey's been used traditionally for, well, ever, really, including the root which historically was more prized than the leaves.
regrow teeth
with knitbone & eggshells :
http://www.typesofteeth.net/teeth-solutions/regrow-teeth/
Knit Bone - Comfrey
My Grandmother used it as a poultice when my brother fell off his bike & fractured his skull and it did heal amazingly quickly!
Comfrey for bones
I once tripped over a bulldog which seemed unmoved and accepted my apology. I had a very painful foot, which felt as though I had broken a bone in my foot. I had some Russian Comfrey in my garden, so tore up a couple or three large leaves, put them in a large bowl, infused them in boiling water then soaked my foot for 20 minutes. as soon as it was cool enough to bear. The pain went away and didn't return.
Now I suspect I have broken my ankle, I'd like to get some more.