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Symphytum

© Marge Talt

Symphytum asperum (synonym Symphytum asperrimum), the prickly or rough comfrey, forage comfrey, Persian comfrey or trottles, is a similar species. Considered a noxious weed in parts of the US, it's gown in Russia for silage, where it was introduced from southwestern Asia.

The basic differences between it and S. officinale are that the stems are not winged, whereas S. officinale always has winged stems with the wings continuing on the stems. Prickly comfrey flowers are initially pink, turning deep blue or purple while common comfrey flowers are typically red to purple, sometimes blue, pale yellow or cream.

Both have fruits containing four nutlets, each with one seed.. Those of common comfrey are glossy black while prickly comfrey's are brown to blackish brown with a finely granular surface and very slightly smaller in size..

Prickly comfrey is also widely distributed in the US from parts of California to British Columbia and the northeastern parts of the country.

Symphytum tuberosum, tuberous comfrey, is a yellow flowered comfrey, more low growing than other species. It's found in woods and other damp, shady places in western, central and southern Europe.

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Symphytum grandiflorum

Symphytum grandiflorum, as I've always known it, but apparently now more correctly termed S. ibericum, is a plant I would not be without. I am (along with most of the web) in some confusion about the correct naming of this species. Most UK sites list S. ibericum, although RHS Plant Finder still has two S. grandiflorum listings, while most US sources list S. grandiflorum. Royal Botanic Gardens, Edinburgh's, Flora Europaea says S. grandiflorum is a synonym for S. ibericum. GRIN says S. grandiflorum is an accepted name and doesn't list S. ibericum at all. Old habits die hard, so I will continue to use the name with which I'm most familiar for the time being. You need to know about the name game, however, as you will likely run into both of them as you troll through the web and nursery catalogs.

All this taxonomic perplexity aside, this is a neat, carpeting plant that gets about a foot high. It spreads fairly quickly by over ground and underground stems and seeds, but can be dug out easily if it exceeds its bounds. The leaves, like other members of the Boraginaceae, are rough and hairy to the touch, and somewhat coarse taken individually. But en masse, it provides a weed-proof cover from sun to dappled shade, remaining somewhat evergreen, for me, in all but the worst winters. It is rated hardy from USDA zones 3 to 9.