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 ssp. holoserica

Ophrys holoserica ssp. tetraloniae

Ophrys holoserica ssp. untchjii

Ophrys incubacea

Ophrys insectifera ssp. insectifera

Ophrys lutea

Ophrys sphegodes ssp.tommasinii

Ophrys tetraloniae

- Ophrys — Synonyme

- Ophrys araneola

- Ophrys sphegodes ssp. araneola

- Ophrys sphegodes ssp. illyrica

- Ophrys sphegodes ssp. incantata

- Ophrys tommasinii

Opopanax chironium

- Opuntia

Opuntia dejecta

Opuntia dillenii

Opuntia ficus-indica

Opuntia tomentosa

- Orchis

Orchis mascula ssp. signifera

Orchis militaris

Orchis papilionacea

Orchis pauciflora

Orchis provincialis

Orchis purpurea

Orchis simia

- Orchis — Synonyme

- Orchis fusca

- Orchis latifolia α majalis

- Orchis majalis

- Orchis maxima

- Orchis morio

- Orchis pyramindalis

- Orchis tridentata

- Orchis ustulata

- 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