Comfrey Yields, Drying
Answered by: Richard Alan Miller
Question from: Linda
Posted on: November 12, 1999

Thank you for your quick response. However you have raised some new questions, such as: how do you dry comfrey and how much comfrey could I expect an acre to produce in dry weight?

Comfrey is cultivated from rootstock. Roots from an older field are quartered and cut into 3 to 5 inch lengths, by hand. They are planted 1.5 to 2.0 inches deep and one foot apart in rows (some recommended planting 4 inches deep, but this can lead to rotting before emergence); 17 to 20 inch furrows. Some 6 to 10 inches of rootstock can be taken from an established field every fourth year, with one acre reseeding five.

It likes nitrogen to encourage the lush leaf growth. Manure adds too many weeds. The taproot can grow to six feet within three years. Comfrey likes a heavy irrigation which it sets up its root system the first year, probably as much as a five-day rotation on well drained soils. Weed control is done by cultivation, however, when the field begins to mature somewhat an "umbrella effect" markedly discourages weed growth. The broad Comfrey leaves compete successfully with many weeds.

Comfrey should be cut before 10% of the crop goes to flower. It cannot be dried in the sun because of high mucilage. Even pellet milled Comfrey will rot from the center. The best form of harvest is to cut at 6 inches from the ground with a side-bar cutter, attempting not to bruise the Leaf as this darkens it.

Root harvest can be done with potato digging equipment, taking care to pile and cover the Roots with tarps, or at least keep them from exposure to the drying effects of the sun. Yields in dry weight for a field established for four year (or more) can be more than five ton per acre on four cuttings. With heavy irrigation, 6 cuttings are possible in some regions.

Let the cut Leaf come to a 50% sun-cure wilt, and then pick it up with a flail-chop to be taken to a drying facility (i.e. Hop Kiln, Corn Dryer, etc.]. Tobacco dryers and plywood kilns are other alternatives for dryers. Comfrey is easy to grow, but the key to success with this crop lies in proper dehydration and handling.

Besides processing the Leaf for the greenish powder, and harvesting the underground Root for drying, there is an opportunity to produce cattle feed alternatives as a 60% Comfrey/40% Alfalfa pellet. This constitutes a "whole food" for cattle. While this might seem rather simple, Comfrey is actually very difficult to handle, requiring some rather sophisticated management techniques.

Most details beyond this first overview are considered proprietary, and will probably require an outside consultant to assist in the harvest, drying, and eventual processing details for ease into the marketplace. Further, the alternative cattlefood supplement market has yet to be developed, requiring further professional help. This is how I currently make a living, working as an outside consultant.

I am available to assist in all phases of development (including marketing). I may be contacted for further details via the Richters website at

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