Oenanthe lachenalii
Parsley Water-dropwort
Oenanthe pimpinelloides
Corky-fruited Water-dropwort
Oenanthe silaifolia
Narrow-leaved Water-dropwort
Onobrychis viciifolia
Sainfoin
Ononis repens
Common Restharrow
Ononis spinosa
Spiny Restharrow
Ophioglossum azoricum
Small Adder's-tongue
Ophioglossum vulgatum
Adder's-tongue
Ophrys apifera
Bee Orchid
Ophrys fuciflora
Late Spider-orchid
Ophrys insectifera
Fly Orchid
Ophrys sphegodes
Early Spider-orchid
Orchis mascula
Early-purple Orchid
Orchis militaris
Military Orchid
Orchis purpurea
Lady Orchid
Orchis simia
Monkey Orchid
Oreopteris limbosperma
Lemon-scented Fern
Origanum vulgare
Wild Marjoram
Ornithogalum pyrenaicum
Spiked Star-of-Bethlehem
Ornithogalum umbellatum
Star-of-Bethlehem
Orobanche caryophyllacea
Bedstraw Broomrape
Orobanche hederae
Ivy Broomrape
Orobanche rapum-genistae
Greater Broomrape
Orthilia secunda
Serrated Wintergreen