There are other plants which in the leaf stage at this time of the year, look like comfrey: borage, alkanet. There's also Foxglove.
There are several comfrey's including - Russian comfrey (ht to 5ft plus in some cases), Soft comfrey, which has white flowers and less coarse leaves than Russian comfrey, Tuberous comfrey (which is not Borage), this has white flowers and not as tall as soft comfrey. Russian comfrey has deep tap-root type roots (and there is a theory that because of these deep roots, they pick up nutrients from the soil which then go up into the leaves and that's why the leaves are good for making comfrey 'juice' as a fertilizer or for putting on the compost heap)
