ABC

- Obione — Synonym

- Obione portulacoides

- Ocimum

Ocimum basilicum

- Ocimum — Synonym

- Ocimum odorum

- Odontites

Odontites luteus

Odontites vernus

Odontites vulgaris

- Oenothera

Oenothera biennis

- Olea

Olea europaea

- Olea — Synonyme

- Olea angustifolia

- Olea latifolia

- Olea pallida

- Olea sativa

- Olearia

Olearia stellulata

- Omalotheca

Omalotheca sylvatica

- Onagra — Synonym

- Onagra biennis

- Onobrychis

Onobrychis viciifolia

- Onobrychis — Synonyme

- Onobrychis viciifolia ssp. sativa

- Onobrychis sativa

- Onoclea — Synonym

- Onoclea struthiopteris

- Ononis

Ononis reclinata

Ononis spinosa agg.

- Ononis — Synonym

- Ononis campestris

- Onopordum

Onopordum acanthium

Onopordum illyricum

- Onosma

Onosma echioides ssp.dalmatica

- Onosma — Synonyme

- Onosma dalmatica

- Onosma javorkae

- Ophioglossum

Ophioglossum vulgatum

- Ophioglossum — Synonym

- Ophioglossum ovatum

- Ophrys

Ophrys apifera

Ophrys bertolonii

Ophrys bombyliflora

Ophrys holoserica agg. Istrien

Ophrys holoserica ssp. holoserica

Ophrys incubacea

Ophrys insectifera ssp. insectifera

Ophrys lutea ssp. lutea

Ophrys sphegodes

Ophrys sphegodes ssp.tommasinii

Ophrys x lyrata

Ophrys zinsmeisteri

- Ophrys — Synonyme

- Ophrys aestivalis

- Ophrys arachnites

- Ophrys araneifera

- Ophrys araneola

- Ophrys aranifera ssp. atrata

- Ophrys aranifera ssp. incubacea

- Ophrys atrata

- Ophrys corsica

- Ophrys fuciflora

- Ophrys fuciflora ssp. untchjii

- Ophrys holosericea ssp. holosericea

- Ophrys insectifera ssp. bertolonii

- Ophrys istriensis

- Ophrys kvarneri

- Ophrys muscifera

- Ophrys myodes

- Ophrys scolopax ssp. cornuta

- Ophrys sphegodes ssp. araneola

- Ophrys sphegodes ssp. atrata

- Ophrys sphegodes ssp. illyrica

- Ophrys sphegodes ssp. incantata

- Ophrys spiralis

- Ophrys tommasinii

- Ophrys untchjii

- Ophrys vespifera

Opopanax chironium

- Opuntia

Opuntia dejecta

Opuntia dillenii

Opuntia ficus-indica

Opuntia tomentosa

- Orchis

Orchis mascula ssp. speciosa

Orchis militaris

Orchis pauciflora

Orchis provincialis

Orchis purpurea

Orchis simia

- Orchis (Synonyme)

- Orchis abortiva

- Orchis albida

- Orchis bifolia

- Orchis chlorantha

- Orchis conopsea

- Orchis cyrilli

- Orchis fuchsii

- Orchis fusca

- Orchis globosa

- Orchis incarnata

- Orchis latifolia ssp. incarnata, Orchis latifolia β incarnata

- Orchis latifolia α majalis

- Orchis maculata

- Orchis maculata ssp. incarnata

- Orchis majalis

- Orchis mascula ssp. signifera

- Orchis maxima

- Orchis militaris ssp. simia

- Orchis miniata

- Orchis morio

- Orchis pallens ssp. provincialis

- Orchis papilionacea

- Orchis provincialis ssp. pauciflora

- Orchis pyramindalis

- Orchis rivini

- Orchis signifera

- Orchis speciosa

- Orchis tridentata

- Orchis ustulata

- Orchis ustulata ssp. aestivalis

- Orchis ustulata ssp. ustulata

- Orchis variegata

- Oreomecon (Synonym)

- Oreomecon alpina ssp. alpina

- Oreomecon alpina ssp. kerneri

- Oreopteris — Synonym

- Oreopteris limbosperma

- Origanum

Origanum majorana

Origanum vulgare ssp. vulgare

- Origanum — Synonym

- Origanum floridum

- Orlaya

Orlaya grandiflora

- Ornithogalum

Ornithogalum kochii

Ornithogalum pyrenaicum

Ornithogalum sp.

Ornithogalum umbellatum

- Ornithogalum — Synonym

- Ornithogalum luteum

- Ornus — Synonym

- Ornus europaea

- Orobanche

Orobanche flava

Orobanche gracilis

Orobanche lutea

Orobanche minor

Orobanche picridis

Orobanche sp.

- Orobanche — Synonyme

- Orobanche picridis-hieracioidis

- Orobanche reichardiae

- Orobus — Synonyme

- Orobus aphaca

- Orobus niger

- Orobus vernus

- Orthodon — Synonym

- Orthodon glomeratum

- Orvala — Synonym

- Orvala garganica

Ostrya carpinifolia

Osyris alba

Otanthus maritimus

- Otites — Synonym

- Otites cuneifolius

- Oxalis

Oxalis acetosella

Oxalis articulata

Oxalis corniculata

Oxalis dillenii

Oxalis pes-caprae

- Oxalis — Synonyme

- Oxalis corniculata var. atropurpurea

- Oxalis corniculata var. dillenii

- Oxalis corniculata var. repens

- Oxalis chilensis

- Oxalis navieri

- Oxalis vulgaris

- Oxycoccos — Synonym

- Oxycoccos palustris

Oxytropis campestris