Oenothera biennis L. (Synonym : Oenothera royfraseri R.R.Gates)

Family : Onagraceae [Naturalized plant]

Oenothera glazioviana Micheli (Synonym : Oenothera fusiformis Munz & I.M.Johnst.)

Family : Onagraceae [Naturalized plant]

Oenothera laciniata Hill (Synonym : Onagra sinuata (L.) Moench)

Family : Onagraceae [Naturalized plant]

Oenothera stricta Ledeb. ex Link (Synonym : Oenothera polymorpha H.Lév. var. stricta (Ledeb. ex Link) H.Lév.)

Family : Onagraceae

Ohwia caudata (Thunb.) H.Ohashi (Synonym : Desmodium caudatum (Thunb.) DC.)

Family : Fabaceae

Oldenlandia corymbosa L. (Synonym : Gerontogea herbacea Cham. & Schltdl.)

Family : Rubiaceae [Naturalized plant]

Oldenlandia diffusa (Willd.) Roxb. (Synonym : Hedyotis diffusa Willd.)

Family : Rubiaceae

Olea europaea L.

Family : Oleaceae

Omphalodes krameri Franch. & Sav.

Family : Boraginaceae

Omphalotrix longipes Maxim.

Family : Scrophulariaceae