giant hogweed achenes detail heracleum mantegazzianum bloom flower blossom cartwheel-flower, western honey bee flying

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