No interactions present.
... whether it's Symphytum asperum or Symphytum x hidcotense.
Superficially it could be either. The first thing one looks at when considering Symphytum is whether the plant is producing stolons. Not possible to tell from a photograph unfortunately. S x hidcotense is stoloniferous and S. asperum is not. However, given that there are only two species with light blue flowers, this is S. asperum on the basis that the calyx is split more than 2/3 of the way to the base (S. asperum is split less that 2/3).
BSBI VC Recorder
comment does not make sense
The explanation was that the two species could not be distinguished in these photograph by their general aspect, not by the presence or absence of stolons (not ascertainable from the photographs), but that they could be distinguished by another feature - the degree of division of the calyx. I was nervous of judging this from a photograph - because of ambiguities arising from viewing angles - but this feature does seem to indicate Symphytum asperum.
I think grizzledbadger's comment refered to the final bracketed reference to S. asperum which should be S. x hidcotense, I presume. Personally I favour the latter given the very pale corollas and the rarity of asperum compared to the increasingly common hidcotense. The photos are a bit over-exposed which makes it harder to be sure.
I'm sorry for the low quality of my pictures, I tried different angles but I was using a device with no "close-up" option. Next time I go to Tower Hamlets I'll bring a proper camera with me.
Lat/Lng: 51.523163740457, -0.025749206542969
OS grid ref: TQ370823
Wonderful historical cemetery, now a natural reserve