# List of plant genus names with etymologies (L–P)

Since the first printing of Carl Linnaeus's Species Plantarum in 1753, plants have been assigned one epithet or name for their species and one name for their genus, a grouping of related species. Many of these plants are listed in Stearn's Dictionary of Plant Names for Gardeners. William Stearn (1911–2001) was one of the pre-eminent British botanists of the 20th century: a Librarian of the Royal Horticultural Society, a president of the Linnean Society and the original drafter of the International Code of Nomenclature for Cultivated Plants.
The first column below contains seed-bearing genera from Stearn and other sources as listed, excluding those names that no longer appear in more modern works, such as Plants of the World by Maarten J. M. Christenhusz (lead author), Michael F. Fay and Mark W. Chase. Plants of the World is also used for the family and order classification for each genus. The second column gives a meaning or derivation of the word, such as a language of origin. The last two columns indicate additional citations.

## Key

    Latin: = derived from Latin (otherwise Greek, except as noted)
    Ba = listed in Ross Bayton's The Gardener's Botanical
    Bu = listed in Lotte Burkhardt's Index of Eponymic Plant Names
    CS = listed in both Allen Coombes's The A to Z of Plant Names and Stearn's Dictionary of Plant Names for Gardeners
    G = listed in David Gledhill's The Names of Plants
    St = listed in Stearn's Dictionary of Plant Names for Gardeners

## Genera

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
Genera :
| Genus | Meaning or derivation | Family | Order | Ref | G |
| Lablab | Arabic name | Fabaceae | Fabales | Ba | G |
| Laburnum | Latin name | Fabaceae | Fabales | CS | G |
| Lacaena | Helen of Troy | Orchidaceae | Asparagales | Bu | |
| Lachnanthes | woolly flowers | Haemodoraceae | Commelinales | St | |
| Lactuca | Latin: milky (the sap) | Asteraceae | Asterales | CS | G |
| Lagarosiphon | narrow tubes | Hydrocharitaceae | Alismatales | St | G |
| Lagarostrobos | loose or narrow cones | Podocarpaceae | Pinales | Ba | G |
| Lagenandra | flask-like male parts (the anthers) | Araceae | Alismatales | St | |
| Lagenaria | flask-like (the fruits) | Cucurbitaceae | Cucurbitales | St | G |
| Lagotis | rabbit ears | Plantaginaceae | Lamiales | St | G |
| Lagurus | rabbit tail (the inflorescences) | Poaceae | Poales | St | G |
| Lamium | Open mouth (the flowers). Latin name. | Lamiaceae | Lamiales | CS | G |
| Lampranthus | shining flowers | Aizoaceae | Caryophyllales | St | G |
| Lamprocapnos | bright smoke | Papaveraceae | Ranunculales | Ba | |
| Lantana | Medieval Latin name | Verbenaceae | Lamiales | CS | G |
| Lapsana | Greek and Latin name | Asteraceae | Asterales | Ba | G |
| Larix | Latin name | Pinaceae | Pinales | CS | G |
| Laserpitium | Latin name | Apiaceae | Apiales | St | G |
| Latania | name from Mauritius | Arecaceae | Arecales | St | G |
| Lathraea | hidden (the parasitic underground stems) | Orobanchaceae | Lamiales | St | G |
| Lathyrus | Greek name | Fabaceae | Fabales | CS | G |
| Laurelia | Latinised Spanish name | Athero­spermataceae | Laurales | St | G |
| Laureliopsis | Laurelia-like | Monimiaceae | Laurales | Ba | |
| Laurus | Latin name | Lauraceae | Laurales | CS | G |
| Lavandula | Latin: washing (used in soap) | Lamiaceae | Lamiales | CS | G |
| Lemna | Greek name | Araceae | Alismatales | St | G |
| Lens | Latin name | Fabaceae | Fabales | St | G |
| Leonotis | lion ears (the flowers) | Lamiaceae | Lamiales | CS | G |
| Leontice | Greek name | Berberidaceae | Ranunculales | Ba | G |
| Leontodon | lion teeth (the leaf edges) | Asteraceae | Asterales | St | G |
| Leontopodium | lion feet | Asteraceae | Asterales | CS | G |
| Leonurus | lion tails (the inflorescences) | Lamiaceae | Lamiales | St | G |
| Lepidium | Greek and Latin name | Brassicaceae | Brassicales | St | G |
| Lepidozamia | scaly Zamia | Zamiaceae | Cycadales | Ba | G |
| Lepismium | scales (around the areoles) | Cactaceae | Caryophyllales | St | |
| Leptinella | slender | Asteraceae | Asterales | Ba | G |
| Leptodermis | thin skin (the bracteoles) | Rubiaceae | Gentianales | St | G |
| Leptopyrum | slender grain (the fruits) | Ranunculaceae | Ranunculales | St | |
| Leptospermum | slender seeds | Myrtaceae | Myrtales | CS | G |
| Leptotes | delicacy (the thin, terete leaves) | Orchidaceae | Asparagales | St | G |
| Lethia | Lethe, a mythological river | Iridaceae | Asparagales | Bu | |
| Leucadendron | white tree (the leaves) | Proteaceae | Proteales | St | G |
| Leucaena | white (the flowers) | Fabaceae | Fabales | St | G |
| Leucanthemum | white flowers | Asteraceae | Asterales | CS | G |
| Leucheria | white | Asteraceae | Asterales | St | G |
| Leucocoryne | white club (the staminodes) | Amaryllidaceae | Asparagales | St | G |
| Leucocrinum | white Crinum | Asparagaceae | Asparagales | St | G |
| Leucogenes | white + (perhaps) nobility | Asteraceae | Asterales | Ba | G |
| Leucojum | white and violet | Amaryllidaceae | Asparagales | CS | G |
| Leucopogon | white beard | Ericaceae | Ericales | Ba | G |
| Leucosceptrum | white scepter | Lamiaceae | Lamiales | Ba | G |
| Leucospermum | white seeds | Proteaceae | Proteales | Ba | G |
| Leucothoe | Greek mythological name | Ericaceae | Ericales | CS | G |
| Levisticum | Latin: (medicinal) relief | Apiaceae | Apiales | CS | G |
| Leymus | anagram of the related Elymus | Poaceae | Poales | Ba | G |
| Liatris | uncertain; possibly booty or bald | Asteraceae | Asterales | CS | G |
| Libocedrus | teardrop Cedrus (cedar resin) | Cupressaceae | Pinales | St | G |
| Licuala | Moluccan name | Arecaceae | Arecales | St | G |
| Ligularia | Latin: strap (the ray florets) | Asteraceae | Asterales | CS | G |
| Ligusticum | Greek name | Apiaceae | Apiales | CS | G |
| Ligustrum | Latin name | Oleaceae | Lamiales | CS | G |
| Lilium | Latin name | Liliaceae | Liliales | CS | G |
| Limnanthes | marsh flowers | Limnanthaceae | Brassicales | St | G |
| Limnobium | marsh life | Hydrocharitaceae | Alismatales | St | |
| Limnocharis | marsh beauty | Alismataceae | Alismatales | St | G |
| Limonium | Meadow. Greek name. | Plumbaginaceae | Caryophyllales | CS | G |
| Linanthus | Linum (flax) flowers | Polemoniaceae | Ericales | St | G |
| Linaria | Linum-like | Plantaginaceae | Lamiales | CS | G |
| Linum | Latin name | Linaceae | Malpighiales | CS | G |
| Liparis | oily (the leaves) | Orchidaceae | Asparagales | St | G |
| Liquidambar | Latin: liquid amber (the resin) | Altingiaceae | Saxifragales | CS | G |
| Liriodendron | lily tree | Magnoliaceae | Magnoliales | CS | G |
| Liriope | Greek mythological name | Asparagaceae | Asparagales | CS | G |
| Litchi | Chinese name | Sapindaceae | Sapindales | St | G |
| Lithocarpus | stone fruit (the nuts) | Fagaceae | Fagales | CS | G |
| Lithodora | stone gift (rocky habitat) | Boraginaceae | Boraginales | CS | G |
| Lithophragma | stone wall. Possibly an error, but some species do grow in stone walls. | Saxifragaceae | Saxifragales | St | G |
| Lithops | stony appearance | Aizoaceae | Caryophyllales | CS | G |
| Lithospermum | stone seeds. Latin name. | Boraginaceae | Boraginales | St | G |
| Lithraea | Chilean name | Anacardiaceae | Sapindales | St | |
| Litsea | Chinese name | Lauraceae | Laurales | St | G |
| Loasa | probably a South American name | Loasaceae | Cornales | St | G |
| Lobularia | Greek and Latin: little pods | Brassicaceae | Brassicales | CS | G |
| Lolium | Latin name | Poaceae | Poales | St | G |
| Lomandra | fringed male parts | Asparagaceae | Asparagales | Ba | G |
| Lomatia | with borders (the seed margins) | Apiaceae | Apiales | CS | G |
| Lomatium | fringe | Apiaceae | Apiales | Ba | G |
| Lonas | (unknown) | Asteraceae | Asterales | St | |
| Lonchocarpus | lance fruit | Fabaceae | Fabales | St | G |
| Lophomyrtus | crested Myrtus | Myrtaceae | Myrtales | Ba | G |
| Lophophora | crest-bearing (the tufts) | Cactaceae | Caryophyllales | St | G |
| Lophospermum | crested seeds | Plantaginaceae | Lamiales | Ba | G |
| Lordhowea | Ontong Java Atoll, formerly the Lord Howe Atoll, in the Solomon Islands | Asteraceae | Asterales | Bu | G |
| Loropetalum | strap petals | Hamamelidaceae | Saxifragales | CS | G |
| Lotus | Greek name | Fabaceae | Fabales | CS | G |
| Luculia | Nepalese name | Rubiaceae | Gentianales | St | G |
| Ludisia | (unknown) | Orchidaceae | Asparagales | Ba | |
| Luffa | Arabic name | Cucurbitaceae | Cucurbitales | St | G |
| Luma | Mapuche name | Myrtaceae | Myrtales | Ba | G |
| Lunaria | Latin: moon-like (the seed pods) | Brassicaceae | Brassicales | CS | G |
| Lupinus | Latin name | Fabaceae | Fabales | CS | G |
| Luzula | possibly Latin: small light (from the dewy sparkle), or yellowish, or Italian for a bioluminescent insect | Juncaceae | Poales | CS | G |
| Lycaste | (unclear) | Orchidaceae | Asparagales | St | G |
| Lycianthes | Lycium + flower | Solanaceae | Solanales | Ba | |
| Lycium | Greek and Latin name for a shrub from Lycia | Solanaceae | Solanales | CS | G |
| Lycopus | wolf foot (the leaves) | Lamiaceae | Lamiales | CS | G |
| Lysichiton | dissolving cloak (the spathes) | Araceae | Alismatales | CS | G |
| Lysionotus | releasing in the back (the capsule suture) | Gesneriaceae | Lamiales | St | G |
| Lythrum | bloody (the flowers) | Lythraceae | Myrtales | CS | G |
| Machaeranthera | sword anthers | Asteraceae | Asterales | Ba | G |
| Machaonia | Machaon, a mythological hero | Rubiaceae | Gentianales | Bu | |
| Macradenia | long gland (pollen stalks) | Orchidaceae | Asparagales | St | G |
| Macrozamia | large Zamia | Zamiaceae | Cycadales | St | G |
| Madhuca | Sanskrit name | Sapotaceae | Ericales | St | |
| Madia | Chilean name | Asteraceae | Asterales | St | G |
| Maesa | Arabic name | Primulaceae | Ericales | St | G |
| Magdalenaea | Santa Maria Madalena, Rio de Janeiro, in Brazil | Orobanchaceae | Lamiales | Bu | |
| Maianthemum | May flowers | Asparagaceae | Asparagales | CS | G |
| Maihuenia | Mapuche name | Cactaceae | Caryophyllales | Ba | |
| Malachra | Malva | Malvaceae | Malvales | St | |
| Mallotus | woolly | Euphorbiaceae | Malpighiales | St | G |
| Malope | Latin name | Malvaceae | Malvales | St | G |
| Malus | Greek and Latin name | Rosaceae | Rosales | CS | G |
| Malva | Latin name | Malvaceae | Malvales | CS | G |
| Malvastrum | Latin: mallow-like | Malvaceae | Malvales | St | G |
| Malvaviscus | Latin: mallow stickiness | Malvaceae | Malvales | St | G |
| Mammea | West Indian name | Calophyllaceae | Malpighiales | St | G |
| Mammillaria | Latin: nippled | Cactaceae | Caryophyllales | St | G |
| Mandragora | Greek and Latin name | Solanaceae | Solanales | St | G |
| Mangifera | Indian name | Anacardiaceae | Sapindales | St | G |
| Manihot | Brazilian name | Euphorbiaceae | Malpighiales | St | G |
| Manilkara | South Indian name | Sapotaceae | Ericales | St | |
| Manulea | Latin: hand, from the finger-like petals | Scrophulariaceae | Lamiales | St | |
| Margyricarpus | pearl fruit | Rosaceae | Rosales | St | G |
| Marrubium | Latin name | Lamiaceae | Lamiales | St | G |
| Mascarenhasia | Mascarene Islands | Apocynaceae | Gentianales | St | G |
| Matricaria | Latin name | Asteraceae | Asterales | St | G |
| Mauritia | Surinamese name | Arecaceae | Arecales | St | |
| Maxillaria | resembling an insect maxilla | Orchidaceae | Asparagales | St | G |
| Mayaca | French Guianese name | Mayacaceae | Poales | St | G |
| Maytenus | Chilean name | Celastraceae | Celastrales | CS | G |
| Mazus | teat, for swellings on the lower lip of the flowers | Mazaceae | Lamiales | CS | G |
| Meconopsis | poppy-like | Papaveraceae | Ranunculales | CS | G |
| Medeola | Medea of mythology | Liliaceae | Liliales | St | G |
| Medicago | Greek and Latin name | Fabaceae | Fabales | St | G |
| Medusagyne | Medusa (a mythological monster) + female parts | Ochnaceae | Malpighiales | Bu | |
| Medusandra | Medusa (a mythological monster) + male parts | Peridiscaceae | Saxifragales | Bu | |
| Medusantha | Medusa (a mythological monster) + flowers | Lamiaceae | Lamiales | Bu | |
| Medusanthera | Medusa (a mythological monster) + flowers | Stemonuraceae | Aquifoliales | Bu | |
| Megahertzia | Roaring Meg falls, or their waterway, in Queensland, Australia | Proteaceae | Proteales | Bu | |
| Megaskepasma | large covering (the bracts) | Acanthaceae | Lamiales | St | |
| Melaleuca | black and white | Myrtaceae | Myrtales | St | G |
| Melampodium | Melampus, a legendary oracle | Asteraceae | Asterales | Bu | |
| Melanthium | dark flowers | Melanthiaceae | Liliales | St | |
| Melasphaerula | black small bulbs | Iridaceae | Asparagales | St | G |
| Melastoma | black mouth. (The berries stain the mouth when eaten.) | Melastomataceae | Myrtales | St | G |
| Melia | Greek name | Meliaceae | Sapindales | CS | G |
| Melianthus | honey flowers, for its nectar | Francoaceae | Geraniales | CS | G |
| Melica | honey, for its sweet sap | Poaceae | Poales | CS | G |
| Melicoccus | honey berries. Previously Melicocca. | Sapindaceae | Sapindales | St | G |
| Melicope | honey cutting | Rutaceae | Sapindales | Ba | G |
| Melicytus | honey jar | Violaceae | Malpighiales | St | G |
| Melilotus | honey lotus or honey clover | Fabaceae | Fabales | St | G |
| Melinis | honey or blackish | Poaceae | Poales | Ba | G |
| Meliosma | honey-scented | Sabiaceae | Proteales | St | G |
| Melissa | honey bee | Lamiaceae | Lamiales | CS | G |
| Melittis | honey-bearing or honey bee | Lamiaceae | Lamiales | CS | G |
| Melliodendron | honey tree | Styracaceae | Ericales | Ba | |
| Melocactus | Latin: melon cactus | Cactaceae | Caryophyllales | St | G |
| Melothria | Greek and Latin name | Cucurbitaceae | Cucurbitales | St | G |
| Menispermum | moon seeds | Menispermaceae | Ranunculales | St | G |
| Mentha | Minthe of mythology | Lamiaceae | Lamiales | CS | G |
| Menyanthes | small flowers or moon flowers | Menyanthaceae | Asterales | CS | G |
| Mercurialis | Mercury of mythology | Euphorbiaceae | Malpighiales | St | G |
| Merope | Merope, one of the mythological Pleiades | Rutaceae | Sapindales | Bu | |
| Meryta | bunching (the male flower heads) | Araliaceae | Apiales | St | G |
| Mesembryanthemum | middle embryo flower (the ovaries) | Aizoaceae | Caryophyllales | St | G |
| Metrosideros | core of iron | Myrtaceae | Myrtales | St | G |
| Meum | Greek and Latin name | Apiaceae | Apiales | CS | G |
| Micranthemum | small flowers | Linderniaceae | Lamiales | St | |
| Microbiota | small Biota (now Platycladus) | Cupressaceae | Pinales | Ba | G |
| Microcachrys | small cones | Podocarpaceae | Pinales | Ba | G |
| Microglossa | small tongue (the ray florets) | Asteraceae | Asterales | St | G |
| Milium | Latin name | Poaceae | Poales | Ba | G |
| Mimosa | mimic (the leaves) | Fabaceae | Fabales | CS | G |
| Mimulus | Latin: little mimic (the flowers) | Phrymaceae | Lamiales | CS | G |
| Mimusops | monkey-face | Sapotaceae | Ericales | St | G |
| Mirabella | Mirabela, Brazil | Cactaceae | Caryophyllales | Bu | |
| Mirabilis | Latin: wonderful | Nyctaginaceae | Caryophyllales | CS | G |
| Miscanthus | stalk-flower (the small flower spikes) | Poaceae | Poales | CS | G |
| Mitella | small caps (the fruit) | Saxifragaceae | Saxifragales | CS | G |
| Mitraria | cap or turban (the fruit or inflorescences) | Gesneriaceae | Lamiales | CS | G |
| Molopospermum | striped seeds | Apiaceae | Apiales | St | G |
| Moluccella | Molucca (unknown connection) | Lamiaceae | Lamiales | CS | G |
| Momordica | Latin: bitten (appearance of the seeds) | Cucurbitaceae | Cucurbitales | St | G |
| Monanthes | single-flowered (the type specimen) | Crassulaceae | Saxifragales | St | |
| Moneses | single (flowered) | Ericaceae | Ericales | St | G |
| Monstera | Latin: monstrous (the leaves) | Araceae | Alismatales | CS | G |
| Morinda | Latin name + Indian | Rubiaceae | Gentianales | St | G |
| Moringa | Latinised Tamil name | Moringaceae | Brassicales | St | G |
| Mormodes | hobgoblin (the odd flowers) | Orchidaceae | Asparagales | St | G |
| Morus | Greek and Latin name | Moraceae | Rosales | CS | G |
| Moscharia | musk | Asteraceae | Asterales | St | |
| Mucuna | Brazilian name | Fabaceae | Fabales | St | G |
| Mukdenia | Mukden (now Shenyang), China | Saxifragaceae | Saxifragales | Ba | |
| Mulgedium | Latin: milking (from the sap) | Asteraceae | Asterales | St | G |
| Musa | Latinised Arabic name; also Antonius Musa (63 BC – 14) | Musaceae | Zingiberales | St | G |
| Muscari | Turkish name | Asparagaceae | Asparagales | CS | G |
| Mussaenda | Latinised Sinhalese name | Rubiaceae | Gentianales | St | G |
| Myoporum | closed pore (spots on the leaves) | Scrophulariaceae | Lamiales | St | G |
| Myosotidium | derived from Myosotis | Boraginaceae | Boraginales | CS | G |
| Myosotis | mouse ear (the leaves) | Boraginaceae | Boraginales | CS | G |
| Myosurus | mouse tail (the flower stalks) | Ranunculaceae | Ranunculales | St | G |
| Myrica | Greek and Latin name | Myricaceae | Fagales | CS | G |
| Myricaria | Myrica-like | Tamaricaceae | Caryophyllales | St | G |
| Myriocephalus | myriad heads (from the compound flower heads) | Asteraceae | Asterales | St | |
| Myriophyllum | myriad leaves | Haloragaceae | Saxifragales | CS | G |
| Myristica | fragrant ointment | Myristicaceae | Magnoliales | St | G |
| Myrmecodia | ant-place | Rubiaceae | Gentianales | Ba | |
| Myroxylon | fragrant-oil wood | Fabaceae | Fabales | St | |
| Myrrhis | Greek name | Apiaceae | Apiales | CS | G |
| Myrsine | Greek name | Primulaceae | Ericales | St | G |
| Myrtillocactus | myrtle cactus (for the myrtle-like fruit) | Cactaceae | Caryophyllales | St | |
| Myrtus | Greek and Latin name | Myrtaceae | Myrtales | CS | G |
| Mystacidium | mustache (the fringes) | Orchidaceae | Asparagales | St | G |
| Najas | naiad | Hydrocharitaceae | Alismatales | St | G |
| Nandina | Japanese name | Berberidaceae | Ranunculales | CS | G |
| Nannorrhops | dwarf bush | Arecaceae | Arecales | St | G |
| Napaea | Napaeae, nymphs of the woods | Malvaceae | Malvales | Bu | |
| Napeanthus | Napaeae (nymphs of the woods) + flowers | Gesneriaceae | Lamiales | Bu | |
| Narcissus | Narcissus of mythology | Amaryllidaceae | Asparagales | CS | G |
| Narthecium | Greek name | Nartheciaceae | Dioscoreales | St | G |
| Nassella | Latin: narrow-necked wicker basket | Poaceae | Poales | Ba | |
| Nasturtium | twisted nose | Brassicaceae | Brassicales | Ba | G |
| Nauclea | ship, possibly | Rubiaceae | Gentianales | St | G |
| Nautilocalyx | nautilus-calyx, possibly | Gesneriaceae | Lamiales | St | |
| Nelumbo | Sinhalese name | Nelumbonaceae | Proteales | St | G |
| Nemastylis | thread column (the styles) | Iridaceae | Asparagales | St | G |
| Nematanthus | thread flower (the flower stalks) | Restionaceae | Poales | St | G |
| Nemesia | Greek name | Scrophulariaceae | Lamiales | CS | G |
| Nemophila | clearing-loving | Hydrophyllaceae | Boraginales | CS | G |
| Neolitsea | new Litsea | Lauraceae | Laurales | Ba | G |
| Nepenthes | antidepressant | Nepenthaceae | Caryophyllales | St | G |
| Nepeta | Latin name | Lamiaceae | Lamiales | CS | G |
| Nephthytis | Nephthys of mythology | Araceae | Alismatales | St | G |
| Neptunia | Neptune of mythology (for its habitat) | Fabaceae | Fabales | St | G |
| Nerine | a sea nymph | Amaryllidaceae | Asparagales | CS | G |
| Nerium | Greek and Latin name | Apocynaceae | Gentianales | CS | G |
| Nertera | low (to the ground) | Rubiaceae | Gentianales | CS | G |
| Nidularium | Latin: little nest | Bromeliaceae | Poales | St | G |
| Nigella | Latin name | Ranunculaceae | Ranunculales | CS | G |
| Niphaea | snowy (the flowers) | Gesneriaceae | Lamiales | St | G |
| Nipponanthemum | Japan flower | Asteraceae | Asterales | Ba | G |
| Nolana | Latin: small bell (the flowers) | Solanaceae | Solanales | St | G |
| Nothofagus | false Fagus | Nothofagaceae | Fagales | CS | G |
| Notholirion | false lily | Liliaceae | Liliales | St | G |
| Notholithocarpus | false Lithocarpus | Fagaceae | Fagales | Ba | |
| Nothoscordum | false garlic | Liliaceae | Liliales | St | G |
| Notylia | back-bumps (on the stigmas) | Orchidaceae | Asparagales | St | |
| Nuphar | Arabic or Persian name | Nymphaeaceae | Nymphaeales | St | G |
| Nyctanthes | night-flowering | Oleaceae | Lamiales | St | G |
| Nymphaea | water nymphs | Nymphaeaceae | Nymphaeales | CS | G |
| Nymphoides | Nymphaea-like | Menyanthaceae | Asterales | St | G |
| Nyssa | Nysa, a water nymph | Nyssaceae | Cornales | CS | G |
| Oberonia | Oberon, a fairy king | Orchidaceae | Asparagales | Bu | |
| Oberonioides | Oberon, a fairy king | Orchidaceae | Asparagales | Bu | |
| Ochna | Greek name | Ochnaceae | Malpighiales | St | G |
| Ocimum | Greek and Latin name | Frankeniaceae | Caryophyllales | CS | G |
| Ocotea | French Guyanese name | Lauraceae | Laurales | St | |
| Octomeria | eight-part (the pollinia) | Orchidaceae | Asparagales | St | |
| Odontadenia | tooth gland (the pistils) | Apocynaceae | Gentianales | St | |
| Odyssea | odyssey or long voyage, a reference to the many genera to which the plant has been assigned | Poaceae | Poales | Bu | |
| Oenanthe | Greek name | Apiaceae | Apiales | St | G |
| Oenocarpus | wine fruit | Arecaceae | Arecales | St | G |
| Oenothera | Greek and Latin name | Onagraceae | Myrtales | CS | G |
| Olea | Latin name | Oleaceae | Lamiales | CS | G |
| Olsynium | little joined (stamens) | Iridaceae | Asparagales | Ba | |
| Omphalea | Omphale, a mythological queen | Euphorbiaceae | Malpighiales | Bu | |
| Omphalodes | navel-like (the seeds) | Boraginaceae | Boraginales | CS | G |
| Omphalogramma | navel-marked (the seeds) | Primulaceae | Ericales | St | G |
| Oncidium | little swelling (on the lips) | Orchidaceae | Asparagales | St | G |
| Oncoba | Arabic name | Salicaceae | Malpighiales | St | G |
| Onobrychis | (unclear) | Fabaceae | Fabales | St | G |
| Ononis | Greek and Latin name | Fabaceae | Fabales | St | G |
| Onopordum | Greek and Latin name | Asteraceae | Asterales | CS | G |
| Onosma | Greek and Latin name | Boraginaceae | Boraginales | St | G |
| Ophiopogon | Greek for a Japanese name | Asparagaceae | Asparagales | CS | G |
| Ophrys | Greek and Latin name | Orchidaceae | Asparagales | St | G |
| Oplismenus | weapons (the appearance of the spikelets) | Poaceae | Poales | St | G |
| Oplopanax | armed Panax (the spines) | Araliaceae | Apiales | St | G |
| Opopanax | sap panacea | Apiaceae | Apiales | St | G |
| Opuntia | Opus, Greece. Latin name. | Cactaceae | Caryophyllales | CS | G |
| Orbea | Latin: discs | Apocynaceae | Gentianales | St | |
| Orchis | testicle (the root tubers) | Orchidaceae | Asparagales | St | G |
| Oreocereus | mountain Cereus | Cactaceae | Caryophyllales | Ba | |
| Oreopanax | mountain Panax | Araliaceae | Apiales | St | G |
| Orestias | Orestes, a mythological hero | Orchidaceae | Asparagales | Bu | |
| Origanum | Greek and Latin name | Lamiaceae | Lamiales | CS | G |
| Orixa | from a Japanese name | Rutaceae | Sapindales | St | G |
| Ormosia | necklace (one use of the seeds) | Fabaceae | Fabales | St | G |
| Ornithogalum | bird's milk (the flowers or bulbs) | Asparagaceae | Asparagales | CS | G |
| Orobanche | Greek and Latin name | Orobanchaceae | Lamiales | St | G |
| Orontium | Greek name | Araceae | Alismatales | CS | G |
| Orostachys | mountain spike | Crassulaceae | Saxifragales | Ba | G |
| Oroxylum | mountain wood (one of its habitats). Previously Oroxylon. | Bignoniaceae | Lamiales | St | |
| Oroya | La Oroya, Peru | Cactaceae | Caryophyllales | Ba | |
| Orphium | Orpheus, a mythological prophet | Gentianaceae | Gentianales | Bu | G |
| Orthaea | Orthaea, one of the mythological Hyacinthides | Ericaceae | Ericales | Bu | |
| Orthocarpus | upright fruit | Orobanchaceae | Lamiales | St | G |
| Orthophytum | straight plant | Bromeliaceae | Poales | Ba | |
| Orthosia | Orthrus, a mythological monster | Apocynaceae | Gentianales | Bu | |
| Orthrosanthus | morning flowers | Iridaceae | Asparagales | St | G |
| Orychophragmus | dug-up partition (the pitted septa) | Brassicaceae | Brassicales | St | |
| Oryza | Latin and Greek name | Poaceae | Poales | St | G |
| Osmanthus | scented flowers | Oleaceae | Lamiales | CS | G |
| Osteomeles | bone apple (the nutlets) | Rosaceae | Rosales | St | G |
| Osteospermum | bone seed | Asteraceae | Asterales | Ba | G |
| Ostrya | Greek and Latin name | Betulaceae | Fagales | CS | G |
| Ostryopsis | Ostrya-like | Betulaceae | Fagales | Ba | G |
| Osyris | Latin name | Santalaceae | Santalales | Bu | G |
| Otatea | Mexican name | Poaceae | Poales | St | |
| Othonna | Greek and Latin name | Asteraceae | Asterales | CS | G |
| Ottelia | from a Malabar name | Hydrocharitaceae | Alismatales | St | G |
| Oxalis | Greek and Latin name | Oxalidaceae | Oxalidales | CS | G |
| Oxera | acid or acrid (the taste of the sap) | Lamiaceae | Lamiales | St | |
| Oxydendrum | sharp tree (the taste of the leaves) | Ericaceae | Ericales | CS | G |
| Oxylobium | sharp small pods | Fabaceae | Fabales | St | G |
| Oxypetalum | sharp petals | Apocynaceae | Gentianales | St | G |
| Oxyria | sharp (the taste) | Polygonaceae | Caryophyllales | St | G |
| Oxytropis | sharp keels (on the flowers) | Fabaceae | Fabales | St | G |
| Oziroe | Oziroe, a nymph | Asparagaceae | Asparagales | Bu | |
| Ozothamnus | strong-smelling shrub | Asteraceae | Asterales | Ba | G |
| Pachira | Guyanese name | Malvaceae | Malvales | St | G |
| Pachycereus | thick cactus | Cactaceae | Caryophyllales | St | |
| Pachycormus | thick, stripped trunk | Anacardiaceae | Sapindales | Ba | |
| Pachyphragma | thick walls (the septa) | Brassicaceae | Brassicales | CS | G |
| Pachyphytum | thick plant | Crassulaceae | Saxifragales | St | G |
| Pachypodium | thick foot | Apocynaceae | Gentianales | Ba | G |
| Pachyrhizus | thick roots | Fabaceae | Fabales | St | G |
| Pachysandra | thick male parts (the stamens) | Buxaceae | Buxales | CS | G |
| Pachystachys | thick spikes | Acanthaceae | Lamiales | CS | G |
| Pachystegia | thick cover | Asteraceae | Asterales | Ba | |
| Paederia | Latin: stinky | Rubiaceae | Gentianales | St | G |
| Paeonia | Greek and Latin name | Paeoniaceae | Saxifragales | CS | G |
| Palaquium | Philippine name | Sapotaceae | Ericales | St | G |
| Paliavana | possibly the palace of the Children of Palhavã in Portugal | Gesneriaceae | Lamiales | Bu | |
| Paliurus | Greek and Latin name | Rhamnaceae | Rosales | St | G |
| Panax | Latin name | Araliaceae | Apiales | St | G |
| Pancratium | Greek and Latin name | Amaryllidaceae | Asparagales | St | G |
| Pandanus | Malay name | Pandanaceae | Pandanales | St | G |
| Pandorea | Pandora of mythology | Bignoniaceae | Lamiales | CS | G |
| Panicum | Latin name | Poaceae | Poales | CS | G |
| Papaver | Latin name | Papaveraceae | Ranunculales | CS | G |
| Paphia | epithet of the goddess Aphrodite of Paphos | Ericaceae | Ericales | Bu | |
| Paphinia | Aphrodite of mythology | Orchidaceae | Asparagales | St | G |
| Paphiopedilum | Aphrodite's slipper (the flower lips) | Orchidaceae | Asparagales | St | G |
| Paraquilegia | similar to Aquilegia. Previously Paraquilega. | Ranunculaceae | Ranunculales | St | G |
| Paraserianthes | almost Serianthes | Fabaceae | Fabales | Ba | G |
| Parietaria | Latin: of walls (one habitat) | Urticaceae | Rosales | St | G |
| Paris | Latin: equal (the leaves) | Melanthiaceae | Liliales | CS | G |
| Parnassia | Mount Parnassus, Greece | Celastraceae | Celastrales | St | G |
| Parochetus | near rivulets (the habitat) | Fabaceae | Fabales | St | G |
| Paronychia | paronychia (a disease that these herbs were said to remedy) | Caryophyllaceae | Caryophyllales | St | G |
| Parthenice | Latin name; also an epithet of the goddess Artemis | Asteraceae | Asterales | Bu | |
| Parthenium | Greek and Latin name | Asteraceae | Asterales | CS | G |
| Parthenocissus | virgin ivy, derived from the common name | Vitaceae | Vitales | CS | G |
| Pasithea | Pasithea, a goddess | Asphodelaceae | Asparagales | Bu | G |
| Paspalum | Greek name | Poaceae | Poales | St | G |
| Passiflora | Latin: passion flowers | Passifloraceae | Malpighiales | CS | G |
| Pastinaca | Latin name | Apiaceae | Apiales | CS | G |
| Pavetta | Sinhalese name | Rubiaceae | Gentianales | St | G |
| Paxistima | thick stigmas | Celastraceae | Celastrales | Ba | G |
| Pedicularis | Latin: louse (from folklore about the plant) | Orobanchaceae | Lamiales | St | G |
| Pediocactus | plains cactus | Cactaceae | Caryophyllales | St | |
| Pelargonium | stork (the beak-shaped fruit) | Geraniaceae | Geraniales | CS | G |
| Pelecyphora | hatchet-bearing (the tubercles) | Cactaceae | Caryophyllales | St | |
| Peltandra | shield-stamens | Araceae | Alismatales | St | G |
| Peltaria | shield-like (the leaves) | Brassicaceae | Brassicales | St | G |
| Peltoboykinia | small-shield Boykinia | Saxifragaceae | Saxifragales | Ba | |
| Peltophorum | shield-bearing (the stigma) | Fabaceae | Fabales | St | G |
| Penelopeia | Penelope, a legendary heroine | Cucurbitaceae | Cucurbitales | Bu | |
| Peniocereus | filament cactus | Cactaceae | Caryophyllales | St | |
| Pennisetum | feather-bristle (the flower spikes) | Poaceae | Poales | CS | G |
| Penstemon | five stamens | Plantaginaceae | Lamiales | CS | G |
| Pentaglottis | five tongues (on the corolla) | Boraginaceae | Boraginales | St | G |
| Pentas | fives (the flower parts) | Rubiaceae | Gentianales | St | G |
| Peperomia | pepper-like | Piperaceae | Piperales | CS | G |
| Pericallis | very beautiful | Asteraceae | Asterales | Ba | G |
| Perilla | possibly Latin: little bag (the calyx) | Lamiaceae | Lamiales | St | G |
| Periploca | entwining (the corolla tubes) | Apocynaceae | Gentianales | St | G |
| Peristeria | dove-like (the orchid columns) | Orchidaceae | Asparagales | St | |
| Peristrophe | around-twisting (the corolla tubes) | Acanthaceae | Lamiales | St | G |
| Persea | Greek name | Lauraceae | Laurales | CS | G |
| Persicaria | leaves like Persica (peach) | Polygonaceae | Caryophyllales | CS | G |
| Petasites | sun-hats (the leaves). Greek name. | Asteraceae | Asterales | CS | G |
| Petrocallis | rock beauty (the habitat) | Brassicaceae | Brassicales | St | G |
| Petrocosmea | rock ornament | Gesneriaceae | Lamiales | Ba | G |
| Petromarula | Cretan name | Campanulaceae | Asterales | St | |
| Petrophile | rock lover. Previously Petrophila. | Proteaceae | Proteales | St | G |
| Petrophytum | rock plant. Previously Petrophyton. | Rosaceae | Rosales | St | G |
| Petrorhagia | rock-breaking | Caryophyllaceae | Caryophyllales | St | G |
| Petroselinum | Greek and Latin name | Apiaceae | Apiales | CS | G |
| Petunia | Tupi–Guarani name | Solanaceae | Solanales | CS | G |
| Peucedanum | Greek and Latin name | Apiaceae | Apiales | CS | G |
| Peumus | Chilean name | Monimiaceae | Laurales | St | G |
| Phacelia | bundles (the flowers) | Hydrophyllaceae | Boraginales | CS | G |
| Phaedranassa | bright queen (the flowers) | Amaryllidaceae | Asparagales | St | G |
| Phaius | twilight (the dark flowers) | Orchidaceae | Asparagales | St | G |
| Phalaenopsis | moth-like | Orchidaceae | Asparagales | St | G |
| Phalaris | Greek and Latin name | Poaceae | Poales | CS | G |
| Phaseolus | Latin name, from a Greek name | Fabaceae | Fabales | CS | G |
| Phebalium | possibly a Greek name | Rutaceae | Sapindales | St | G |
| Phellodendron | cork tree | Rutaceae | Sapindales | CS | G |
| Philesia | loving | Philesiaceae | Liliales | St | G |
| Phillyrea | Greek name | Oleaceae | Lamiales | CS | G |
| Philodendron | tree-loving (they are epiphytes) | Araceae | Alismatales | CS | G |
| Philotheca | loving box | Rutaceae | Sapindales | Ba | |
| Philyra | Greek name; also from Philyra, a nymph | Euphorbiaceae | Malpighiales | Bu | |
| Phleum | Greek name | Poaceae | Poales | St | G |
| Phlomis | flame (a use of the leaves) | Lamiaceae | Lamiales | CS | G |
| Phlox | flame (the flowers) | Polemoniaceae | Ericales | CS | G |
| Phoebanthus | bright (an epithet of the god Apollo) + flower | Asteraceae | Asterales | Bu | |
| Phoebe | Phoebe, a goddess | Lauraceae | Laurales | Bu | |
| Phoenix | Greek name | Arecaceae | Arecales | CS | G |
| Pholidota | scaly | Orchidaceae | Asparagales | St | G |
| Phormium | basket or mat (uses of the leaf fibres) | Asphodelaceae | Asparagales | CS | G |
| Photinia | shining (the foliage) | Rosaceae | Rosales | CS | G |
| Phragmipedium | partition slipper (the slipper-shaped lips) | Orchidaceae | Asparagales | St | |
| Phragmites | fence or hedge reeds | Poaceae | Poales | CS | G |
| Phuopsis | Valeriana-like | Rubiaceae | Gentianales | CS | G |
| Phygelius | fleeing the sun (they prefer shade) | Scrophulariaceae | Lamiales | CS | G |
| Phyla | tribes (probably the flower clusters) | Verbenaceae | Lamiales | St | G |
| Phylica | leafy | Rhamnaceae | Rosales | St | G |
| Phyllagathis | leafy ball of thread (the bracts) | Melastomataceae | Myrtales | St | |
| Phyllanthus | leaf-flowers (the source of some flowers) | Phyllanthaceae | Malpighiales | St | G |
| Phyllis | Latin name; also from Phyllis, a mythological princess | Rubiaceae | Gentianales | Bu | |
| Phyllocladus | leaf-branch (the flattened branches) | Podocarpaceae | Pinales | St | G |
| Phyllodoce | Nereid of mythology | Ericaceae | Ericales | St | G |
| Phyllostachys | leaf spike (the inflorescences) | Poaceae | Poales | CS | G |
| Physalis | bladders (the appearance of the fruit) | Solanaceae | Solanales | CS | G |
| Physaria | bladder-like | Brassicaceae | Brassicales | Ba | G |
| Physocarpus | bladder fruit | Ranunculaceae | Ranunculales | CS | G |
| Physochlaina | bladder covering (the inflated calyx) | Solanaceae | Solanales | CS | G |
| Physoplexis | bladder weaving (the corolla) | Campanulaceae | Asterales | St | G |
| Physostegia | bladder roofing (the inflated calyx) | Lamiaceae | Lamiales | St | G |
| Phytelephas | plant-elephant (for the ivory-like nut) | Arecaceae | Arecales | St | G |
| Phyteuma | Greek and Latin name | Campanulaceae | Asterales | St | G |
| Phytolacca | plant lac | Phytolaccaceae | Caryophyllales | CS | G |
| Picea | Latin name | Pinaceae | Pinales | CS | G |
| Picrasma | bitterness | Simaroubaceae | Sapindales | Ba | G |
| Pieris | Pieria, the home of the mythological Muses | Ericaceae | Ericales | CS | G |
| Pilea | Latin: caps (the shape of the calyx) | Urticaceae | Rosales | CS | G |
| Pilosella | hairy + little | Asteraceae | Asterales | Ba | G |
| Pilosocereus | hairy Cereus | Cactaceae | Caryophyllales | Ba | |
| Pimelea | fat or lard (its oils) | Thymelaeaceae | Malvales | St | G |
| Pimenta | Spanish name | Myrtaceae | Myrtales | St | G |
| Pimpinella | from a Medieval Latin name | Apiaceae | Apiales | St | G |
| Pinanga | Malayan name | Arecaceae | Arecales | St | |
| Pinguicula | fatty (the leaves) | Lentibulariaceae | Lamiales | St | G |
| Pinus | Latin name | Pinaceae | Pinales | CS | G |
| Piper | Latin name, from Sanskrit and Greek names | Piperaceae | Piperales | St | G |
| Piptadenia | falling glands (of the stamens) | Fabaceae | Fabales | St | G |
| Piptanthus | falling flowers (all parts fall at the same time) | Fabaceae | Fabales | CS | G |
| Piscidia | Latin: fish-killing (a use of the plant) | Fabaceae | Fabales | St | G |
| Pistacia | Greek and Latin name | Anacardiaceae | Sapindales | CS | G |
| Pistia | water | Araceae | Alismatales | CS | G |
| Pisum | Greek and Latin name | Fabaceae | Fabales | CS | G |
| Pithecellobium | Greek rendering of a Brazilian name for "monkey's earring" (the fruit) | Fabaceae | Fabales | St | G |
| Pittosporum | tar seeds | Pittosporaceae | Apiales | CS | G |
| Plagianthus | asymmetrical flowers | Poaceae | Poales | St | G |
| Plagiobothrys | oblique scars (on the nutlets) | Boraginaceae | Boraginales | St | |
| Plantago | Latin name | Plantaginaceae | Lamiales | CS | G |
| Platanus | Greek and Latin name | Platanaceae | Proteales | CS | G |
| Platycarya | broad nuts | Juglandaceae | Fagales | St | G |
| Platycladus | broad branches | Cupressaceae | Pinales | Ba | G |
| Platycodon | broad bell (the flowers) | Campanulaceae | Asterales | CS | G |
| Platystemon | broad stamens | Papaveraceae | Ranunculales | St | |
| Plectranthus | spur-flowers | Lamiaceae | Lamiales | CS | G |
| Pleioblastus | many buds | Poaceae | Poales | CS | G |
| Pleione | Pleione of mythology | Orchidaceae | Asparagales | CS | G |
| Pleiospilos | many spots (on the leaves) | Aizoaceae | Caryophyllales | St | G |
| Pleurothallis | side or rib branches (perhaps the inflorescences or stems) | Orchidaceae | Asparagales | St | |
| Plumbago | Latin name | Plumbaginaceae | Caryophyllales | CS | G |
| Poa | Greek name | Poaceae | Poales | CS | G |
| Podachaenium | stalked achenes | Asteraceae | Asterales | St | |
| Podalyria | Podalirius of mythology | Fabaceae | Fabales | St | G |
| Podocarpus | stalked fruit | Podocarpaceae | Pinales | CS | G |
| Podolepis | foot of scales (the pedicels) | Asteraceae | Asterales | St | G |
| Podophyllum | foot-leaves (for the resemblance to duck's feet) | Berberidaceae | Ranunculales | CS | G |
| Podranea | anagram of the related Pandorea | Bignoniaceae | Lamiales | St | G |
| Pogonatherum | bearded awn (the glumes) | Poaceae | Poales | St | G |
| Pogonia | bearded (the fringed lips) | Orchidaceae | Asparagales | St | |
| Pogostemon | bearded stamens | Lamiaceae | Lamiales | St | |
| Polemonium | Greek and Latin name | Polemoniaceae | Ericales | CS | G |
| Poliothyrsis | grey panicles | Salicaceae | Malpighiales | St | G |
| Polygala | Greek and Latin name | Polygalaceae | Fabales | CS | G |
| Polygonatum | Greek and Latin name | Asparagaceae | Asparagales | CS | G |
| Polygonum | Greek and Latin name | Polygonaceae | Caryophyllales | St | G |
| Polylepis | many scales | Rosaceae | Rosales | Ba | G |
| Polymnia | Polyhymnia, a Muse | Asteraceae | Asterales | Bu | |
| Polyscias | many sun-shades (the umbels) | Araliaceae | Apiales | St | G |
| Polyspora | many seeds | Theaceae | Ericales | Ba | |
| Polystachya | many spikes (on the inflorescences) | Orchidaceae | Asparagales | St | G |
| Pomaderris | lid of skin (on the capsules) | Rhamnaceae | Rosales | St | G |
| Populus | Latin name | Salicaceae | Malpighiales | CS | G |
| Porana | possibly from a Marathi name | Convolvulaceae | Solanales | St | G |
| Portulaca | Latin name | Portulacaceae | Caryophyllales | St | G |
| Portulacaria | Portulaca-like | Didiereaceae | Caryophyllales | St | |
| Posidonia | Poseidon, a god | Posidoniaceae | Alismatales | Bu | G |
| Posoqueria | Guianan name | Rubiaceae | Gentianales | St | |
| Potamogeton | Greek and Latin name | Potamo­getonaceae | Alismatales | St | G |
| Potentilla | Latin: potent (medicinally) | Rosaceae | Rosales | CS | G |
| Pothos | Sinhalese name | Araceae | Alismatales | St | G |
| Pouteria | Carib name | Sapotaceae | Ericales | St | |
| Premna | stump | Lamiaceae | Lamiales | St | G |
| Prenanthes | downward-facing flowers | Asteraceae | Asterales | St | G |
| Primula | Medieval Latin name | Primulaceae | Ericales | CS | G |
| Primulina | Primula-like | Gesneriaceae | Lamiales | Ba | G |
| Proboscidea | (elephant) trunks (the fruit) | Martyniaceae | Lamiales | St | G |
| Procris | Procris, a mythological princess | Urticaceae | Rosales | Bu | |
| Promenaea | Promenaea, a Greek priestess of Dodona | Orchidaceae | Asparagales | St | |
| Prometheum | Prometheus, a god | Crassulaceae | Saxifragales | Bu | |
| Prosartes | appendage | Liliaceae | Liliales | Ba | |
| Proserpinaca | Latin name | Haloragaceae | Saxifragales | St | G |
| Prosopis | Greek name | Fabaceae | Fabales | St | G |
| Prospero | Prospero of William Shakespeare's The Tempest | Asparagaceae | Asparagales | Bu | |
| Prostanthera | addition to the anther (the spurs) | Lamiaceae | Lamiales | CS | G |
| Protea | Proteus of mythology | Proteaceae | Proteales | St | G |
| Prumnopitys | hindmost pine | Podocarpaceae | Pinales | Ba | G |
| Prunella | from a German name | Lamiaceae | Lamiales | CS | G |
| Prunus | Latin name | Rosaceae | Rosales | CS | G |
| Psammophora | sandy | Aizoaceae | Caryophyllales | St | |
| Pseuderanthemum | false Eranthemum | Acanthaceae | Lamiales | St | G |
| Pseudocydonia | false Cydonia | Rosaceae | Rosales | Ba | G |
| Pseudofumaria | false Fumaria | Papaveraceae | Ranunculales | CS | |
| Pseudogynoxys | false Gynoxis | Asteraceae | Asterales | Ba | |
| Pseudolarix | false Larix | Pinaceae | Pinales | CS | G |
| Pseudopanax | false Panax | Araliaceae | Apiales | CS | G |
| Pseudophoenix | false Phoenix | Arecaceae | Arecales | St | G |
| Pseudosasa | false Sasa | Poaceae | Poales | CS | G |
| Pseudotsuga | false Tsuga | Pinaceae | Pinales | CS | G |
| Pseudowintera | false Wintera (Drimys) | Winteraceae | Canellales | CS | G |
| Psidium | Latin name, from a Greek name | Myrtaceae | Myrtales | St | G |
| Psophocarpus | noisy fruit (the exploding capsules) | Fabaceae | Fabales | St | |
| Psoralea | scabby | Fabaceae | Fabales | St | G |
| Psychotria | from a Greek name | Rubiaceae | Gentianales | St | G |
| Ptelea | Greek name | Rutaceae | Sapindales | CS | G |
| Pteridophyllum | fern leaves | Papaveraceae | Ranunculales | St | G |
| Pterocarya | winged nuts | Juglandaceae | Fagales | CS | G |
| Pteroceltis | winged Celtis | Cannabaceae | Rosales | Ba | G |
| Pterocephalus | winged head (the feathery fruiting heads) | Caprifoliaceae | Dipsacales | St | G |
| Pterospermum | winged seeds | Malvaceae | Malvales | St | |
| Pterostyrax | winged Styrax | Styracaceae | Ericales | CS | G |
| Ptychosperma | folded seeds | Arecaceae | Arecales | St | G |
| Pulicaria | Latin name | Asteraceae | Asterales | St | G |
| Pulmonaria | Latin: lungs, from the supposed resemblance to diseased lungs | Boraginaceae | Boraginales | CS | G |
| Pulsatilla | (unclear) | Ranunculaceae | Ranunculales | St | G |
| Punica | Latin name | Lythraceae | Myrtales | CS | G |
| Puya | Chilean name of Puya chilensis | Bromeliaceae | Poales | CS | G |
| Pycnanthemum | dense flowers | Lamiaceae | Lamiales | St | G |
| Pycnostachys | dense spikes | Lamiaceae | Lamiales | St | G |
| Pyracantha | fire thorns | Rosaceae | Rosales | CS | G |
| Pyrola | diminutive of Pyrus | Ericaceae | Ericales | St | G |
| Pyrostegia | fire roofs, from the upper lip | Bignoniaceae | Lamiales | St | G |
| Pyrus | Latin name | Rosaceae | Rosales | CS | G |
| Pyxidanthera | boxed anthers (with lids) | Diapensiaceae | Ericales | St | G |