blossoms closeup flower flowering plant forest grass Grass Family Heracleum (plant) nature plant tiny white wild Wildflower England english flowers Great Britain Heracleum sphondylium hogweed natural stalks stems summer Umbelliferae umbels wild wiltshire biennial cow parsnip grasses rural Apiaceae creepy dead Finished flowerhead giant hogweed head Heracleum mantegazzianum invasive macabre spent stem Sussex toxic umbel umbellifer