Op - Oz
| Ophioglossum azoricum | Natternzunge Azoren | Small Adderstongue | Ophioglossaceae |
| Ophioglossum lusitanicum | Natternzunge Portugiesische | Least Adderstongue | Ophioglossaceae |
| Ophioglossum vulgatum | Natternzunge Gewöhnliche | Southern Adderstongue | Ophioglossaceae |
| Ophrys aegea | Ragwurz Ägäische | Aegean Ophrys | Orchidaceae |
| Ophrys aesculapii | Ragwurz Äskulap | Asklepios' Ophrys | Orchidaceae |
| Ophrys apifera | Ragwurz Bienen | Bee Orchid | Orchidaceae |
| Ophrys arachnitiformis | Ragwurz Spinnenähnliche | False Spider Orchid | Orchidaceae |
| Ophrys araneola | Ragwurz Spinnen Kleine | Small Spider Orchid | Orchidaceae |
| Ophrys argolica | Ragwurz Argolis | Argolis- Ophrys | Orchidaceae |
| Ophrys atlantica | Ragwurz Atlas | Atlas Ophrys | Orchidaceae |
| Ophrys aveyronensis | Ragwurz Aveyron | Aveyron- Ophrys | Orchidaceae |
| Ophrys balearica | Ragwurz Balearen | Balearic Ophrys | Orchidaceae |
| Ophrys bertolonii | Ragwurz Bertolonis | Bertoloni's Ophrys | Orchidaceae |
| Ophrys bertoloniiformis | Ragwurz Bertolonis Falsche | False Bertoloni's Ophrys | Orchidaceae |
| Ophrys biancae | Ragwurz Bianca | Bianca's Ophrys | Orchidaceae |
| Ophrys biscutella | Ragwurz Brillen | Shield Ophrys | Orchidaceae |
| Ophrys bombyliflora | Ragwurz Drohnen | Bumblebee Ophrys | Orchidaceae |
| Ophrys calliantha | Ragwurz Schnabel Prächtige | Splendid Ophrys | Orchidaceae |
| Ophrys candica | Ragwurz Weißglanz | Enamel Ophrys | Orchidaceae |
| Ophrys catalaunica | Ragwurz Katalonische | Catalunya Ophrys | Orchidaceae |
| Ophrys crabronifera | Ragwurz Hornissen | Hornet Ophrys | Orchidaceae |
| Ophrys conradiae | Ragwurz Conrads | Conrad's Ophrys | Orchidaceae |
| Ophrys cretica | Ragwurz Kretische | Cretan Ophrys | Orchidaceae |
| Ophrys delphinensis | Ragwurz Delphi | Delphi- Ophrys | Orchidaceae |
| Ophrys epirotica | Ragwurz Epirus | Epirus Ophrys | Orchidaceae |
| Ophrys explanata | Ragwurz Ausgebreitete | Catalunya Ophrys | Orchidaceae |
| Ophrys ferrum- equinum | Ragwurz Hufeisen | Horseshoe Ophrys | Orchidaceae |
| Ophrys fusca | Ragwurz Braune | Dull Ophrys | Orchidaceae |
| Ophrys gortynia | Ragwurz Gortyn | Gortyn Ophrys | Orchidaceae |
| Ophrys heldreichii | Ragwurz Heldreichs | Heldreich's Ophrys | Orchidaceae |
| Ophrys helenae | Ragwurz Helena | Helena's Ophrys | Orchidaceae |
| Ophrys heterochila | Ragwurz Dodekanes | Dodekanes Ophrys | Orchidaceae |
| Ophrys holoserica | Ragwurz Hummel | Late Spider Orchid | Orchidaceae |
| Ophrys incubacea | Ragwurz Schwarze | Black Ophrys | Orchidaceae |
| Ophrys insectifera | Ragwurz Fliegen | Fly Orchid | Orchidaceae |
| Ophrys iricolor | Ragwurz Regenbogen | Rainbow Ophrys | Orchidaceae |
| Ophrys lacaitae | Ragwurz Lacaitas | Lacaita's Ophrys | Orchidaceae |
| Ophrys lesbis | Ragwurz Lesbos | Lesbos Ophrys | Orchidaceae |
| Ophrys lucis | Ragwurz Licht | Bright Ophrys | Orchidaceae |
| Ophrys lunulata | Ragwurz Halbmond | Crescent Ophrys | Orchidaceae |
| Ophrys lutea | Ragwurz Gelbe | Yellow Ophrys | Orchidaceae |
| Ophrys mammosa | Ragwurz Busen | Mammosa Ophrys | Orchidaceae |
| Ophrys morisii | Ragwurz Moris | Moris' Ophrys | Orchidaceae |
| Ophrys oestrifera | Ragwurz Gehörnte | Horned Ophrys | Orchidaceae |
| Ophrys omegaifera | Ragwurz Omega | Omega Ophrys | Orchidaceae |
| Ophrys oxyrrhynchos | Ragwurz Schnabel | Beaked Ophrys | Orchidaceae |
| Ophrys pallida | Ragwurz Bleiche | Pale Ophrys | Orchidaceae |
| Ophrys promontorii | Ragwurz Vorgebirgs | Promontorio del Monte Gargano Ophrys | Orchidaceae |
| Ophrys passionis | Ragwurz Oster | Passion Ophrys | Orchidaceae |
| Ophrys philippei | Ragwurz Philippes | Philippe's Ophrys | Orchidaceae |
| Ophrys regis- ferdinandi | Ragwurz König Ferdinand | Earwig Ophrys | Orchidaceae |
| Ophrys reinholdii | Ragwurz Reinholds | Reinhold's Ophrys | Orchidaceae |
| Ophrys rhodia | Ragwurz Nabel Rhodische | Rhodian Ophrys | Orchidaceae |
| Ophrys scolopax | Ragwurz Schnepfen | Woodcock Ophrys | Orchidaceae |
| Ophrys spruneri | Ragwurz Spruners | Spruner's Ophrys | Orchidaceae |
| Ophrys subfusca | Ragwurz Gelbrandige | Yellow Ophrys | Orchidaceae |
| Ophrys speculum | Ragwurz Spiegel | Mirror Ophrys | Orchidaceae |
| Ophrys sphegodes | Ragwurz Spinnen | Early Spider Orchid | Orchidaceae |
| Ophrys subfusca | Ragwurz Gelbrandige | Yellow Ophrys | Orchidaceae |
| Ophrys tardans | Ragwurz Spätblühende | Late flowering Ophrys | Orchidaceae |
| Ophrys tenthredinifera | Ragwurz Wespen | Sawfly Ophrys | Orchidaceae |
| Ophrys umbilicata | Ragwurz Nabel | Carmel Ophrys | Orchidaceae |
| Opopanax chironium | Heilwurz Cheiron | Chiron Sweet Myrrh | Apiaceae |
| Opopanax hispidus | Heilwurz Borstige | Hispid Sweet Myrrh | Apiaceae |
| Oreoselinum majus | Haarstrang Berg | Mountain Parsley | Apiaceae |
| Orchis anatolica | Knabenkraut Anatolisches | Anatolian Orchid | Orchidaceae |
| Orchis anthropophora | Ohnhorn | Man Orchid | Orchidaceae |
| Orchis italica | Knabenkraut Italienisches | Italian Orchid | Orchidaceae |
| Orchis mascula | Knabenkraut Stattliches | Early Purple Orchid | Orchidaceae |
| Orchis militaris | Knabenkraut Helm | Military Orchid | Orchidaceae |
| Orchis pallens | Knabenkraut Bleiches | Pale- flowered Orchid | Orchidaceae |
| Orchis patens | Knabenkraut Atlas | Green- spotted Orchid | Orchidaceae |
| Orchis pauciflora | Knabenkraut Armblütiges | Sparsely- flowering Orchid | Orchidaceae |
| Orchis prisca | Knabenkraut Kretisches | Forgotten Orchid | Orchidaceae |
| Orchis provincialis | Knabenkraut Provence | Provence Orchid | Orchidaceae |
| Orchis punctulata | Knabenkraut Punktiertes | Small- dotted Orchid | Orchidaceae |
| Orchis purpurea | Knabenkraut Purpur | Lady Orchid | Orchidaceae |
| Orchis quadripunctata | Knabenkraut Vierpunkt | Four- spotted Orchid | Orchidaceae |
| Orchis simia | Knabenkraut Affen | Monkey Orchid | Orchidaceae |
| Orchis spitzelii | Knabenkraut Spitzels | Spitzel's Orchid | Orchidaceae |
| Orchis x beyrichii | Knabenkraut Beyrichs | Beyrich's Orchid | Orchidaceae |
| Orchis x hausknechtii | Knabenkraut Hausknechts | Hausknecht's Orchid | Orchidaceae |
| Orchis x hybrida | Knabenkraut Hybrid | Lady Orchid | Orchidaceae |
| Oreojuncus monanthos | Binse Einblütige | Host's Rush | Juncaceae |
| Oreojuncus trifidus | Binse Dreiblatt | Highland Rush | Juncaceae |
| Oreopteris limbosperma | Bergfarn | Mountain Fern | Thelypteridaceae |
| Origanum calcaratum | Dost Kalkliebender | Dittany of Amorgos | Lamiaceae |
| Origanum compactum | Dost Gedrungener | Compact Majoram | Lamiaceae |
| Origanum dictamnus | Dost Diptam | Dittany of Crete | Lamiaceae |
| Origanum lirium | Dost Liri | Dittany of Liri | Lamiaceae |
| Origanum majorana | Majoran Garten | Sweet Majoram | Lamiaceae |
| Origanum microphyllum | Dost Kleinblättriger | Small- leaved Majoram | Lamiaceae |
| Origanum onites | Dost Türkischer | Turkish Oregano | Lamiaceae |
| Origanum scabrum | Dost Griechischer | Dittany of Greece | Lamiaceae |
| Origanum sipyleum | Dost Sipylos | Sipylos Majoram | Lamiaceae |
| Origanum symes | Dost Simit | Dittany of Simi | Lamiaceae |
| Origanum vetteri | Dost Vetters | Vetter's Majoram | Lamiaceae |
| Origanum vulgare | Dost Echter | Wild Majoram | Lamiaceae |
| Origanum x majoricum | Majoran Winterharter | Hardy Majoram | Lamiaceae |
| Orlaya daucoides | Breitsame Flachfrüchtiger | Flat- fruited Orlaya | Apiaceae |
| Orlaya daucorlaya | Breitsame Möhrenähnlicher | Carrot Orlaya | Apiaceae |
| Orlaya grandiflora | Breitsame Strahlen | Large- flowered Orlaya | Apiaceae |
| Ormosolenia alpina | Haarstrang Kretischer | Cretan Parsley | Apiaceae |
| Ornithogalum amphibolum | Milchstern Zweifelhafter | Ambigous Star of Bethlehem | Hyacinthaceae |
| Ornithogalum arabicum | Milchstern Arabischer | Large Star of Bethlehem | Hyacinthaceae |
| Ornithogalum armeniacum | Milchstern Armenischer | Armenian Star of Bethlehem | Hyacinthaceae |
| Ornithogalum atticum | Milchstern Attischer | Attic Star of Bethlehem | Hyacinthaceae |
| Ornithogalum baeticum | Milchstern Baetischer | Baetian Star of Bethlehem | Hyacinthaceae |
| Ornithogalum boucheanum | Milchstern Bouchés | Bouché's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum bourgaeanum | Milchstern Bourgeaus | Bourgeau's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum brachystylum | Milchstern Kurzgriffeliger | Short- styled Star of Bethlehem | Hyacinthaceae |
| Ornithogalum brevistylum | Milchstern Pyramiden | Pyramidal Star of Bethlehem | Hyacinthaceae |
| Ornithogalum broteroi | Milchstern Broteros | Brotero's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum collinum | Milchstern Hügel | Hill Star of Bethlehem | Hyacinthaceae |
| Ornithogalum concinnum | Milchstern Hübscher | Neat Star of Bethlehem | Hyacinthaceae |
| Ornithogalum creticum | Milchstern Kretischer | Cretan Star of Bethlehem | Hyacinthaceae |
| Ornithogalum dictaeum | Milchstern Dikti | Dikti Star of Bethlehem | Hyacinthaceae |
| Ornithogalum divergens | Milchstern Spreizender | Lesser Star of Bethlehem | Hyacinthaceae |
| Ornithogalum exaratum | Milchstern Gefurchter | Furrowed Star of Bethlehem | Hyacinthaceae |
| Ornithogalum exscapum | Milchstern Schaftloser | Scapeless Star of Bethlehem | Hyacinthaceae |
| Ornithogalum fimbriatum | Milchstern Gefranster | Fringed Star of Bethlehem | Hyacinthaceae |
| Ornithogalum gussonei | Milchstern Gussones | Gussone's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum insulare | Milchstern Insel | Island Star of Bethlehem | Hyacinthaceae |
| Ornithogalum kochii | Milchstern Kochs | Koch's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum montanum | Milchstern Berg | Mountain Star of Bethlehem | Hyacinthaceae |
| Ornithogalum narbonense | Milchstern Narbonne | Southern Star of Bethlehem | Hyacinthaceae |
| Ornithogalum naxense | Milchstern Naxos | Naxos Star of Bethlehem | Hyacinthaceae |
| Ornithogalum nutans | Milchstern Nickender | Drooping Star of Bethlehem | Hyacinthaceae |
| Ornithogalum oligophyllum | Milchstern Wenigblättriger | Few- leaf Star of Bethlehem | Hyacinthaceae |
| Ornithogalum orthophyllum | Milchstern Geradblättriger | Straight- leaved Star of Bethlehem | Hyacinthaceae |
| Ornithogalum pannonicum | Milchstern Pannonischer | Tufted Star of Bethlehem | Hyacinthaceae |
| Ornithogalum prasinantherum | Milchstern Grünmänniger | Green- anthered Star of Bethlehem | Hyacinthaceae |
| Ornithogalum pumilum | Milchstern Zwerg | Dwarf Star of Bethlehem | Hyacinthaceae |
| Ornithogalum pyrenaicum | Milchstern Pyrenäen | Pyrenean Star of Bethlehem | Hyacinthaceae |
| Ornithogalum refractum | Milchstern Zurückgeknickter | Refracted Star of Bethlehem | Hyacinthaceae |
| Ornithogalum reverchonii | Milchstern Reverchons | Reverchon's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum sibthorpii | Milchstern Sibthorps | Sibthorp's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum spetae | Milchstern Spetas | Speta's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum sphaerocarpum | Milchstern Kugelfrüchtiger | White Pyrenees Star of Bethlehem | Hyacinthaceae |
| Ornithogalum ulixis | Milchstern Odysseus' | Ulysses's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum umbellatum | Milchstern Dolden | White Star of Bethlehem | Hyacinthaceae |
| Ornithogalum visianicum | Milchstern Visianis | Visiani's Star of Bethlehem | Hyacinthaceae |
| Ornithogalum vulgare | Milchstern Gewöhnlicher | Common Star of Bethlehem | Hyacinthaceae |
| Ornithogalum wiedemannii | Milchstern Wiedemanns | Wiedemann's Star of Bethlehem | Hyacinthaceae |
| Ornithopus compressus | Vogelfuß Zusammengedrückter | Compressed Bird's-foot | Fabaceae |
| Ornithopus perpusillus | Vogelfuß Kleiner | Little White Bird's-foot | Fabaceae |
| Ornithopus pinnatus | Vogelfuß Nackter | Ebracteate Bird's-foot | Fabaceae |
| Ornithopus sativus | Vogelfuß Großer | Common Bird's-foot | Fabaceae |
| Orobanche coerulescens | Sommerwurz Blaue | Bluish Broomrape | Orobanchaceae |
| Orobanche gracilis | Sommerwurz Blutrote | Slender Broomrape | Orobanchaceae |
| Orthilia secunda | Birngrün | Sidebells Wintergreen | Ericaceae |
| Osmunda regalis | Rispenfarn Königs | Royal Fern | Osmundaceae |
| Ostericum palustre | Engelwurz Sumpf | Marsh Angelica | Apiaceae |
| Ostrya carpinifolia | Hopfenbuche Europäische | European Hop- Hornbeam | Betulaceae |
| Ostrya japonica | Hopfenbuche Japanische | Japanese Hop- Hornbeam | Betulaceae |
| Ostrya virginiana | Hopfenbuche Virginische | American Hop- Hornbeam | Betulaceae |
| Ottelia alismoides | Ottelie Froschlöffelähnliche | Duck Lettuce | Hydrocharitaceae |
| Oxalis acetosella | Sauerklee Wald | Common Woodsorrel | Oxalidaceae |
| Oxalis adenophylla | Sauerklee Kordilleren | Chilean Woodsorrel | Oxalidaceae |
| Oxalis articulata | Sauerklee Rosa | Pink Woodsorrel | Oxalidaceae |
| Oxalis bowiei | Sauerklee Bowie | Redflower Woodsorrel | Oxalidaceae |
| Oxalis corniculata | Sauerklee Gehörnter | Creeping Yellow Woodsorrel | Oxalidaceae |
| Oxalis debilis | Sauerklee Brasilianischer | Large- flowered Pink Woodsorrel | Oxalidaceae |
| Oxalis decaphylla | Sauerklee Zehnblättriger | Tenleaf Woodsorrel | Oxalidaceae |
| Oxalis dillenii | Sauerklee Dillenius | Slender Yellow Woodsorrel | Oxalidaceae |
| Oxalis exilis | Sauerklee Kleinster | Least Yellow Woodsorrel | Oxalidaceae |
| Oxalis incarnata | Sauerklee Bleicher | Crimson Woodsorrel | Oxalidaceae |
| Oxalis latifolia | Sauerklee Breitblättriger | Broadleaf Woodsorrel | Oxalidaceae |
| Oxalis pes- caprae | Sauerklee Nickender | African Woodsorrel | Oxalidaceae |
| Oxalis purpurea | Sauerklee Purpur | Purple Woodsorrel | Oxalidaceae |
| Oxalis repens | Sauerklee Kriechender | Creeping Woodsorrel | Oxalidaceae |
| Oxalis stricta | Sauerklee Aufrechter | Yellow Woodsorrel | Oxalidaceae |
| Oxalis tetraphylla | Sauerklee Vierblättriger | Iron Cross | Oxalidaceae |
| Oxalis vulcanicola | Sauerklee Buschiger | Volcanic Woodsorrel | Oxalidaceae |
| Oxybasis chenopodioides | Gänsefuß Dickblättriger | Low Goosefoot | Chenopodiaceae |
| Oxybasis glauca | Gänsefuß Graugrüner | Saw- blade Goosefoot | Chenopodiaceae |
| Oxybasis rhombifolia | Gänsefuß Sägeblättriger | Red Goosefoot | Chenopodiaceae |
| Oxybasis rubra | Gänsefuß Roter | Red Goosefoot | Chenopodiaceae |
| Oxybasis urbica | Gänsefuß Straßen | City Goosefoot | Chenopodiaceae |
| Oxyria digyna | Säuerling Alpen | Alpine Mountain Sorrel | Polygonaceae |
| Oxytropis amethystea | Spitzkiel Amethyst | Amethyst Milkvetch | Fabaceae |
| Oxytropis campestris | Spitzkiel Alpen | Yellow Milkvetch | Fabaceae |
| Oxytropis caputoi | Spitzkiel Caputos | Caputo's Milkvetch | Fabaceae |
| Oxytropis dinarica | Spitzkiel Dinarischer | Dinarian Milkvetch | Fabaceae |
| Oxytropis fetida | Spitzkiel Drüsiger | Glandular Milkvetch | Fabaceae |
| Oxytropis foucaudii | Spitzkiel Foucauds | Foucaud's Milkvetch | Fabaceae |
| Oxytropis halleri | Spitzkiel Hallers | Haller's Milkvetch | Fabaceae |
| Oxytropis helvetica | Spitzkiel Schweizer | Suisse Milkvetch | Fabaceae |
| Oxytropis jacquinii | Spitzkiel Jacquins | Jacquin's Milkvetch | Fabaceae |
| Oxytropis jabalambrensis | Spitzkiel Sierra de Javalambre | Sierra de Javalambre Milkvetch | Fabaceae |
| Oxytropis korabensis | Spitzkiel Korab | Korab Milkvetch | Fabaceae |
| Oxytropis lapponica | Spitzkiel Lappländer | Northern Milkvetch | Fabaceae |
| Oxytropis neglecta | Spitzkiel Verkannter | Neglected Milkvetch | Fabaceae |
| Oxytropis ocrensis | Spitzkiel Mt. Ocre | Mt. Ocre Milkvetch | Fabaceae |
| Oxytropis pilosa | Spitzkiel Zottiger | Wooly Milkvetch | Fabaceae |
| Oxytropis prenja | Spitzkiel Prenj | Prenj Milkvetch | Fabaceae |
| Oxytropis purpurea | Spitzkiel Purpur | Purple Milkvetch | Fabaceae |
| Oxytropis triflora | Spitzkiel Dreiblütiger | Three- flowered Milkvetch | Fabaceae |
| Oxytropis tomoriensis | Spitzkiel Mt. Tomor | Mt. Tomor Milkvetch | Fabaceae |