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

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