This table lists all species profiled on PIER with the genus beginning with the letter O. An alphabetical index to all PIER species is also available. Also, the complete alphabetical of all PIER species is available, but it is a large list and may take a while to load on systems with slower internet connections. It includes those of environmental concern (including those that are probably of threat only to islands with high elevations) as well as agricultural and ruderal weeds. Each species is linked by its scientific name to an individual write-up containing relevant information.
Species are listed in alphabetic order. You can browse this list or use the "find" function on your web browser to search by scientific name.
Can't find it here? Check the list of synonyms for other names (the more common synonyms are included below) or search other lists and databases available on the Internet.
Stumped by botanical terms? Here are links to a brief glossary and a search engine for botanical terms.
| Scientific name (+Family) | Often-used other Latin names | Habit |
Present on
Pacific Islands? |
Primarily a threat
at high elevations? |
| Oceaniopteris gibba (Blechnaceae) | Blechnum gibbum (Labill.) Mett.; Lomaria gibba Labill. | fern | Yes | No |
| Ochna integerrima (Ochnaceae) | Elaeocarpus integerrimus Lour. | shrub/tree | No | No |
| Ochna kirkii (Ochnaceae) | shrub/tree | Yes | No | |
| Ochna serrulata (Ochnaceae) | shrub | Yes | No | |
| Ochna thomasiana (Ochnaceae) | shrub | Yes | No | |
| Ochroma pyramidale (Malvaceae) | Ochroma lagopus Sw. | tree | Yes | No |
| Ochrosia elliptica (Apocynaceae) | tree | Yes | No | |
| Ocimum basilicum (Lamiaceae) | herb | Yes | No | |
| Ocimum gratissimum (Lamiaceae) | herb | Yes | No | |
| Odontonema cuspidatum (Acanthaceae) | Odontonema strictum hort.; Thyrsacanthus cuspidatus Nees | shrub | Yes | No |
| Odontonema tubaeforme (Acanthaceae) | Justicia coccinea hort.; Justicia tubaeformis Bertol.; Odontonema strictum (Nees) O. Kuntze; Odontonema tubiforme (Bertol.) Kuntze; Thyrsacanthus strictus Nees | shrub | Yes | No |
| Oenocarpus bataua (Arecaceae) | Jessenia bataua (Mart.) Burret; Jessenia oligocarpa Griseb. & H. Wendl.; Jessenia polycarpa H. Karst.; Oenocarpus oligocarpus (Griseb. & H. Wendl.) Wess. Boer | tree | No | No |
| Oenothera laciniata (Onagraceae) | herb | Yes | No | |
| Oenothera picensis (Onagraceae) | herb | Yes | Yes | |
| Oenothera rosea (Onagraceae) | herb | Yes | Yes | |
| Oenothera stricta subsp. stricta (Onagraceae) | Oenothera striata Link | herb | Yes | Yes |
| Oldenlandia corymbosa (Rubiaceae) | Hedyotis corymbosa (L.) Lam. | herb | Yes | No |
| Oldenlandia pumila (Rubiaceae) | Hedyotis pumila L. f. | herb | Yes | No |
| Olea europaea (Oleaceae) | tree | Yes | No | |
| Olyra latifolia (Poaceae) | Olyra paniculata Sw. | grass | No | No |
| Oncosperma tigillarium (Arecaceae) | Areca tigillaria Jack; Euterpe filamentosa Kunth; Oncosperma filamentosum (Kunth) Blume | tree | Yes | No |
| Operculina ventricosa (Convolvulaceae) | Operculina turpethum (L.) Silva Manso var. ventricosa (Bertero) Austin & Staples | vine | Yes | No |
| Oplismenus burmannii (Poaceae) | grass | Yes | No | |
| Oplismenus compositus (Poaceae) | Panicum compositum L. | grass | Yes | No |
| Oplismenus hirtellus (Poaceae) | Oplismenus hirtellus subsp. setarius (Lam.) Mez ex Ekman; Oplismenus setarius (Lam.) Roem. & Schult. | grass | Yes | No |
| Opuntia dillenii (Cactaceae) | cactus | Yes | No | |
| Opuntia ficus-indica (Cactaceae) | Cactus ficus-indica L.; Opuntia gymnocarpa F. A. C. Weber; Opuntia maxima Mill. | cactus | Yes | No |
| Opuntia fulgida (Cactaceae) | Cylindropuntia fulgida (Engelm.) F. M. Knuth | cactus | No | No |
| Opuntia monacantha (Cactaceae) | Opuntia vulgaris auct. mult. | cactus | Yes | No |
| Opuntia stricta (Cactaceae) | cactus | Yes | No | |
| Origanum majorana (Lamiaceae) | Majorana hortensis Moench; Majorana majorana (L.) H. Karst. | herb | Yes | No |
| Ormosia monosperma (Fabaceae) | Ormosia dasycarpa A. B. Jacks.; Sophora monosperma Sw. | tree | Yes | No |
| Oroxylum indicum (Bignoniaceae) | Arthrophyllum ceylanicum Miq.; Arthrophyllum reticulatum Blume ex Miq.; Bignonia indica L.; Bignonia lugubris Salisb.; Bignonia pentandra Lour.; Bignonia quadripinnata Blanco; Bignonia tripinnata Noronha; Bignonia tuberculata Roxb. ex DC.; Calosanthes indica (L.) Blume; Hippoxylon indica (L.) Raf.; Oroxylum flavum Rehder; Spathodea indica (L.) Pers. | tree | Yes | No |
| Orthosiphon aristatus (Lamiaceae) | Clerodendranthus spicatus (Thunb.) C. Y. Wu ex H. W. Li; Clerodendrum spicatum Thunb.; Ocimum aristatum Blume; Orthosiphon stamineus Benth. | herb | Yes | No |
| Osmoxylon lineare (Araliaceae) | Boerlagiodendron lineare Merr. | shrub | Yes | No |
| Ossaea marginata (Melastomataceae) | Clidemia marginata (Desr.) DC.; Melastoma marginata Desr.; Pentossaea marginata (Desr.) Judd | shrub | No | No |
| Ottelia alismoides (Hydrocharitaceae) | Stratiotes alismoides L. | aquatic herb | No | No |
| Ottelia ovalifolia (Hydrocharitaceae) | Damasonium ovalifolium R. Br. | aquatic herb | Yes | No |
| Ottochloa nodosa (Poaceae) | Panicum nodosum Kunth | grass | No | No |
| Oxalis barrelieri (Oxalidaceae) | Oxalis bahiensis sensu auct. Micr. non Prog. | herb | Yes | No |
| Oxalis corniculata (Oxalidaceae) | Oxalis repens Thunb. | herb | Yes | No |
| Oxalis debilis (Oxalidaceae) | Oxalis corymbosa DC. | herb | Yes | No |
| Oxalis latifolia (Oxalidaceae) | Ionoxalis vallicola Rose; Oxalis vallicola (Rose) R. Knuth | herb | Yes | No |
| Oxalis micrantha (Oxalidaceae) | herb | Yes | No | |
| Oxalis pes-caprae (Oxalidaceae) | Oxalis cernua Thunb. | herb | Yes | No |
| Oxalis purpurea (Oxalidaceae) | herb | Yes | Yes | |
| Oxybasis glauca (Chenopodiaceae) | Chenopodium glaucum L. | herb | Yes | No |
| Oxyspora paniculata (Melastomataceae) | shrub | Yes | No |