| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| PEST6 | Penstemon stenophyllus (Gray) T.J. Howell | Sonoran beardtongue | Scrophulariaceae
|
| PEST | Penstemon stephensii Brandeg. | Stephens' penstemon | Scrophulariaceae
|
| PEST9 | Penstemon strictiformis Rydb. | Mancos penstemon | Scrophulariaceae
|
| PESTA | Penstemon strictus Benth. ssp. angustus Pennell | Penstemon strictus | Scrophulariaceae
|
| PESTS | Penstemon strictus Benth. ssp. strictiformis (Rydb.) Keck | Penstemon strictiformis | Scrophulariaceae
|
| PEST2 | Penstemon strictus Benth. | Rocky Mountain penstemon | Scrophulariaceae
|
| PESU2 | Penstemon subglaber Rydb. | smooth penstemon | Scrophulariaceae
|
| PESU6 | Penstemon subserratus Pennell | finetooth beardtongue | Scrophulariaceae
|
| PESU7 | Penstemon subulatus M.E. Jones | hackberry beardtongue | Scrophulariaceae
|
| PESU10 | Penstemon sudans M.E. Jones | Susanville beardtongue | Scrophulariaceae
|
| PESU13 | Penstemon suffrutescens Rydb. | Penstemon crandallii ssp. crandallii | Scrophulariaceae
|
| PESU8 | Penstemon superbus A. Nels. | superb beardtongue | Scrophulariaceae
|
| PETE4 | Penstemon tenuiflorus Pennell | eastern whiteflower beardtongue | Scrophulariaceae
|
| PETE3 | Penstemon tenuis Small | sharpsepal beardtongue | Scrophulariaceae
|
| PETES | Penstemon ternatus Torr. ex Gray ssp. septentrionalis (Munz & Johnston) Keck | Keckiella ternata ssp. septentrionalis | Scrophulariaceae
|
| PETE15 | Penstemon ternatus Torr. ex Gray | Keckiella ternata ssp. ternata | Scrophulariaceae
|
| PETE9 | Penstemon teucrioides Greene | germander beardtongue | Scrophulariaceae
|
| PETHJ | Penstemon thompsoniae (Gray) Rydb. ssp. jaegeri Keck | Jaeger's beardtongue | Scrophulariaceae
|
| PETHT2 | Penstemon thompsoniae (Gray) Rydb. ssp. thompsoniae | Thompson's beardtongue | Scrophulariaceae
|
| PETHD | Penstemon thompsoniae (Gray) Rydb. var. desperatus Neese | Penstemon thompsoniae ssp. thompsoniae | Scrophulariaceae
|
| PETH2 | Penstemon thompsoniae (Gray) Rydb. | Thompson's beardtongue | Scrophulariaceae
|
| PETHA | Penstemon thurberi Torr. var. anestius Reveal & Beatley | Penstemon thurberi | Scrophulariaceae
|
| PETH3 | Penstemon thurberi Torr. | Thurber's penstemon | Scrophulariaceae
|
| PETI2 | Penstemon tidestromii Pennell | Tidestrom's beardtongue | Scrophulariaceae
|
| PETI3 | Penstemon tiehmii N. Holmgren | Tiehm's beardtongue | Scrophulariaceae
|
| PETOB | Penstemon tolmiei Hook. ssp. brachyanthus (Pennell) Keck | Penstemon procerus var. brachyanthus | Scrophulariaceae
|
| PETOF | Penstemon tolmiei Hook. ssp. formosus (A. Nels.) Keck | Penstemon procerus var. formosus | Scrophulariaceae
|
| PETO3 | Penstemon tolmiei Hook. | Penstemon procerus var. tolmiei | Scrophulariaceae
|
| PETO4 | Penstemon torreyi Benth. | Penstemon barbatus ssp. torreyi | Scrophulariaceae
|
| PETR | Penstemon tracyi Keck | Trinity penstemon | Scrophulariaceae
|
| PETRI | Penstemon triflorus Heller ssp. integrifolius Pennell | Heller's beardtongue | Scrophulariaceae
|
| PETRT2 | Penstemon triflorus Heller ssp. triflorus | Heller's beardtongue | Scrophulariaceae
|
| PETRI2 | Penstemon triflorus Heller var. integrifolius (Pennell) Cory | Penstemon triflorus ssp. integrifolius | Scrophulariaceae
|
| PETR2 | Penstemon triflorus Heller | Heller's beardtongue | Scrophulariaceae
|
| PETRD | Penstemon triphyllus Dougl. ex Lindl. ssp. diphyllus (Rydb.) Keck | Penstemon diphyllus | Scrophulariaceae
|
| PETR6 | Penstemon triphyllus Dougl. ex Lindl. | Riggin's penstemon | Scrophulariaceae
|
| PETUA | Penstemon tubiflorus Nutt. var. achoreus Fern. | white wand beardtongue | Scrophulariaceae
|
| PETUT | Penstemon tubiflorus Nutt. var. tubiflorus | white wand beardtongue | Scrophulariaceae
|
| PETU | Penstemon tubiflorus Nutt. | white wand beardtongue | Scrophulariaceae
|
| PETU2 | Penstemon tusharensis N. Holmgren | Tushar Range beardtongue | Scrophulariaceae
|
| PEUI | Penstemon uintahensis Pennell | Uinta Mountain beardtongue | Scrophulariaceae
|
| PEUN | Penstemon unilateralis Rydb. | oneside penstemon | Scrophulariaceae
|
| PEUT | Penstemon utahensis Eastw. | Utah penstemon | Scrophulariaceae
|
| PEVA2 | Penstemon variabilis Suksdorf | Penstemon deustus var. variabilis | Scrophulariaceae
|
| PEVA3 | Penstemon vaseyanus Greene | Penstemon rydbergii var. rydbergii | Scrophulariaceae
|
| PEVE6 | Penstemon venosus (Keck) Reveal | Penstemon angustifolius var. venosus | Scrophulariaceae
|
| PEVE2 | Penstemon venustus Dougl. ex Lindl. | Venus penstemon | Scrophulariaceae
|
| PEVI3 | Penstemon virens Pennell ex Rydb. | Front Range beardtongue | Scrophulariaceae
|
| PEVIA2 | Penstemon virgatus Gray ssp. arizonicus (Gray) Keck | Penstemon deaveri | Scrophulariaceae
|
| PEVIA | Penstemon virgatus Gray ssp. asa-grayi Crosswhite | Penstemon unilateralis | Scrophulariaceae
|
| PEVIP | Penstemon virgatus Gray ssp. pseudoputus Crosswhite | Penstemon pseudoputus | Scrophulariaceae
|
| PEVIP2 | Penstemon virgatus Gray ssp. putus (A. Nels.) Crosswhite | Penstemon putus | Scrophulariaceae
|
| PEVIA3 | Penstemon virgatus Gray var. asa-grayi (Crosswhite) Dorn | Penstemon unilateralis | Scrophulariaceae
|
| PEVI4 | Penstemon virgatus Gray | upright blue beardtongue | Scrophulariaceae
|
| PEWA8 | Penstemon wardii Gray | Ward's beardtongue | Scrophulariaceae
|
| PEWA9 | Penstemon washingtonensis Keck | Washington beardtongue | Scrophulariaceae
|
| PEWAL2 | Penstemon watsonii Gray ssp. laxus (A. Nels.) Keck | Penstemon laxus | Scrophulariaceae
|
| PEWA | Penstemon watsonii Gray | Watson's penstemon | Scrophulariaceae
|
| PEWH3 | Penstemon wherryi Pennell | Penstemon arkansanus | Scrophulariaceae
|
| PEWH | Penstemon whippleanus Gray | Whipple's penstemon | Scrophulariaceae
|
| PEWHD | Penstemon whitedii Piper ssp. dayanus (T.J. Howell) Keck | Penstemon eriantherus var. argillosus | Scrophulariaceae
|
| PEWHT | Penstemon whitedii Piper ssp. tristis Pennell & Keck | Penstemon eriantherus var. redactus | Scrophulariaceae
|
| PEWH4 | Penstemon whitedii Piper | Penstemon eriantherus var. whitedii | Scrophulariaceae
|
| PEWI | Penstemon wilcoxii Rydb. | Wilcox's penstemon | Scrophulariaceae
|
| PEWI4 | Penstemon wisconsinensis Pennell | Penstemon gracilis var. wisconsinensis | Scrophulariaceae
|
| PEWR2 | Penstemon wrightii Hook. | Wright's beardtongue | Scrophulariaceae
|
| PEYA2 | Penstemon yampaensis Penl. | Yampa beardtongue | Scrophulariaceae
|
| PENST | Penstemon Schmidel | beardtongue | Scrophulariaceae
|
| PEAL19 | Pentachaeta alsinoides Greene | tiny pygmydaisy | Asteraceae
|
| PEAP2 | Pentachaeta aphantochaeta Greene | Pentachaeta exilis ssp. exilis | Asteraceae
|
| PEAU3 | Pentachaeta aurea Nutt. | golden chaetopappa | Asteraceae
|
| PEBE | Pentachaeta bellidiflora Greene | whiteray pygmydaisy | Asteraceae
|
| PEEXA | Pentachaeta exilis (Gray) Gray ssp. aeolica Van Horn & Ornduff | meager pygmydaisy | Asteraceae
|
| PEEXE | Pentachaeta exilis (Gray) Gray ssp. exilis | meager pygmydaisy | Asteraceae
|
| PEEXA2 | Pentachaeta exilis (Gray) Gray var. aphantochaeta Gray | Pentachaeta exilis ssp. exilis | Asteraceae
|
| PEEXD | Pentachaeta exilis (Gray) Gray var. discoidea Gray | Pentachaeta exilis ssp. exilis | Asteraceae
|
| PEEXG | Pentachaeta exilis (Gray) Gray var. grayi Jepson | Pentachaeta bellidiflora | Asteraceae
|
| PEEX4 | Pentachaeta exilis (Gray) Gray | meager pygmydaisy | Asteraceae
|
| PEFR6 | Pentachaeta fragilis Brandeg. | fragile pygmydaisy | Asteraceae
|
| PELY4 | Pentachaeta lyonii Gray | Lyon's pygmydaisy | Asteraceae
|
| PEOR8 | Pentachaeta orcuttii Gray | Pentachaeta aurea | Asteraceae
|
| PEPA35 | Pentachaeta paleacea Greene | Pentachaeta aurea | Asteraceae
|
| PENTA5 | Pentachaeta Nutt. | pygmydaisy | Asteraceae
|
| PEMA20 | Pentaclethra macrophylla Benth. | oilbean tree | Fabaceae
|
| PENTA9 | Pentaclethra Benth. | pentaclethra | Fabaceae
|
| PEBU4 | Pentadesma butyracea Sabine | butter tree | Clusiaceae
|
| PENTA8 | Pentadesma Sabine | pentadesma | Clusiaceae
|
| PESE10 | Pentaglottis sempervirens (L.) Tausch ex Bailey | evergreen bugloss | Boraginaceae
|
| PENTA2 | Pentaglottis Tausch | pentaglottis | Boraginaceae
|
| PEPA40 | Pentagramma pallida (Weatherby) Yatskievych, Windham & Wollenweber | pale silverback fern | Pteridaceae
|
| PETRM | Pentagramma triangularis (Kaulfuss) Yatskievych, Windham & Wollenweber ssp. maxonii (Weatherby) Yatskievych, Windham & Wollenweber | Maxon's goldback fern | Pteridaceae
|
| PETRS | Pentagramma triangularis (Kaulfuss) Yatskievych, Windham & Wollenweber ssp. semipallida (J.T. Howell) Yatskievych, Windham & Wollenweber | goldback fern | Pteridaceae
|
| PETRT | Pentagramma triangularis (Kaulfuss) Yatskievych, Windham & Wollenweber ssp. triangularis | goldback fern | Pteridaceae
|
| PETRV | Pentagramma triangularis (Kaulfuss) Yatskievych, Windham & Wollenweber ssp. viscosa (D.C. Eat.) Yatskievych, Windham & Wollenweber | silverback fern | Pteridaceae
|
| PETR7 | Pentagramma triangularis (Kaulfuss) Yatskievych, Windham & Wollenweber | goldback fern | Pteridaceae
|
| PENTA10 | Pentagramma Yatskievych, Windham & Wollenweber | goldback fern | Pteridaceae
|
| PELU3 | Pentalinon luteum (L.) B.F. Hansen & Wunderlin | hammock viper's-tail | Apocynaceae
|
| PENTA4 | Pentalinon Voigt | pentalinon | Apocynaceae
|
| PEOU | Pentanisia ouranogyne S. Moore | | Rubiaceae
|
| PENTA11 | Pentanisia Harv. | pentanisia | Rubiaceae
|
| PEPH2 | Pentapetes phoenicea L. | flor impia | Sterculiaceae
|