bloom giant hogweed heracleum mantegazzianum flower blossom cartwheel-flower, western honey bee flying insects blooming

giant 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 achenes saw neophyte asia blooming reduces wild rhubarb green rhizome wildflower collect phototoxic biodiversity eliminates gatecrasher contamination herbicides mechanically bushes calamity disaster large biomass