giant hogweed heracleum mantegazzianum leaf leaves flower blossom cartwheel-flower, western honey bee flying insects

giant leaves invasive hogweed leaf plant heracleum mantegazzianum bloom bee flowers blossom expansive cartwheel parsnip hogsbane flower species dangerous plants caucasus eurasia fruits intruder cow parsley achenes saw neophyte asia blooming reduces wild rhubarb green rhizome wildflower collect phototoxic biodiversity eliminates gatecrasher contamination herbicides mechanically bushes calamity disaster large biomass