Comfrey: A tonic for plants and bees but toxic for us


Comfrey growing on the author's steep bank. (Barbara Damrosch)
Contributor July 2, 2014

There is a narrow patch of ground about 200 feet long, right in the middle of our farm, that is completely unlike any other. Everywhere else you’ll find tidy beds with straight rows, bursting with nutritious food crops. But this strip is overgrown with tall grass and a succession of beautiful wildflowers.

Early multicolored lupines are followed by white daisies, red and yellow hawkweed, white yarrow, red clover, yellow buttercups and a big stand of blue-flowered comfrey. Later in the summer, goldenrod will dominate, along with tansy.

Barbara Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.” View Archive

Only the goldenrod is native, but the bees don’t care, and I wish I could say that this anarchic swath has been left for them. But its extreme steepness is what has saved it. Only by clutching at daisies can it be climbed, and only with a scythe can it be mowed, and for this year at least, the bees and I have had our way.

The comfrey, however, is up for debate. It is a mighty plant, almost impossible to kill because its deep, thick roots are merely encouraged by being grubbed out: Even small bits left in the ground will regenerate. So we can slow its habit of creeping into the main greenhouse but not halt it.

What’s interesting about comfrey is that it was long considered a miracle plant and a great hope for the future of organic farming. Thanks to allantoin, a substance it contains that causes cells to multiply, healers have used it since ancient times to set bones, close wounds and treat burns. An old country name for it was knitbone. Its mucilaginous nature also made it a good salve.

In the 1870s a Quaker researcher in England named Henry Doubleday produced a Russian hybrid of it while searching for a cold-hardy plant for the making of postage stamp glue. Doubleday then introduced comfrey as a forage crop for livestock, with limited success (not all animals would eat it), but more than he’d had with glue.

Taking up the banner in the 1950s, Lawrence D. Hills, the founder of the Henry Doubleday Research Association (now called Garden Organic), wrote books and pamphlets lauding comfrey’s use for compost-making, green-manuring and mulching — as well as for human consumption and a feed for chickens. It does produce massive amounts of organic matter, and it is very high in potassium.

But before you delve into this history to find Lawrence’s recipe for comfrey au gratin with rice, you should note that the plant is highly toxic. We now know it contains pyrrolizidine alkaloids that are thought to be carcinogenic and known to cause liver damage. It’s not uncommon for plant substances to both cure and kill, and they demand great skill on the part of a practitioner. I, for one, have no plans to put comfrey inside my body.

A 1974 article by noted author Nancy Bubel called “Growing and Using Comfrey Leaves” in Mother Earth News praises the plant for all its old uses. But the magazine has added a more contemporary note advising readers of its poisonous nature and of the ban on selling it for oral and internal use in the United States and several other countries.

Meanwhile, our comfrey blooms. We could probably smother it with a very large tarp. The bees find its blue flowers’ structure awkward and would not miss it. But it is one part of a colorful picture in early summer.

Tip of the week: Cucumber seeds can be sown now for a second crop in late summer. Give cucumber plants room to grow, enriched soil and plenty of moisture. Thin seedlings to 12 inches apart and four feet between rows. Trellis-grown vines can be planted more densely for a greater harvest. — Adrian Higgins

Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”

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