As White Comfrey (Symphytum orientale) fades on the allotment another takes its place- Common Comfrey (Symphytum officinale) which has shot up in the past few weeks. Or it may be so-called Russian Comfrey which is a widespread cross between Common Comfrey and Prickly Comfrey (Symphytum asperum).
 I can't tell the difference and they hybridise back and forth very freely. Bees don't make the distinction and make straight for it.