| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| HERPE | Herpetineuron (C. Müll.) Card. | herpetineuron moss | Anomodontaceae
|
| HESA12 | Herpothallon sanguineum (Sw.) Tobler | Cryptothecia rubrocincta | Arthoniaceae
|
| HECR5 | Herpothamnus crassifolius (Andr.) Small | Vaccinium crassifolium ssp. crassifolium | Ericaceae
|
| HEHO7 | Herrickia horrida Woot. & Standl. | Eurybia horrida | Asteraceae
|
| HEAL16 | Herteliana alaskensis (Nyl.) S. Ekman | | Bacidiaceae
|
| HERTE | Herteliana P. James | herteliana | Bacidiaceae
|
| HEAD3 | Herzogiella adscendens (Lindb.) Iwats. & Schof. | herzogiella moss | Hypnaceae
|
| HESE6 | Herzogiella seligeri (Brid.) Iwats. | Seliger's herzogiella moss | Hypnaceae
|
| HEST5 | Herzogiella striatella (Brid.) Iwats. | herzogiella moss | Hypnaceae
|
| HETU2 | Herzogiella turfacea (Lindb.) Iwats. | herzodiella moss | Hypnaceae
|
| HERZO | Herzogiella Broth. | herzogiella moss | Hypnaceae
|
| HEFU2 | Hesperaloe funifera (K. Koch) Trel. | New Mexico false yucca | Agavaceae
|
| HEPAE | Hesperaloe parviflora (Torr.) Coult. var. engelmannii (Krauskopf) Trel. | Engelmann's false yucca | Agavaceae
|
| HEPAP | Hesperaloe parviflora (Torr.) Coult. var. parviflora | redflower false yucca | Agavaceae
|
| HEPA8 | Hesperaloe parviflora (Torr.) Coult. | redflower false yucca | Agavaceae
|
| HESPE | Hesperaloe Engelm. | false yucca | Agavaceae
|
| HEACA | Hesperevax acaulis (Kellogg) Greene var. acaulis | stemless dwarf-cudweed | Asteraceae
|
| HEACA2 | Hesperevax acaulis (Kellogg) Greene var. ambusticola Morefield | stemless dwarf-cudweed | Asteraceae
|
| HEACR | Hesperevax acaulis (Kellogg) Greene var. robustior Morefield | stemless dwarf-cudweed | Asteraceae
|
| HEAC8 | Hesperevax acaulis (Kellogg) Greene | stemless dwarf-cudweed | Asteraceae
|
| HECA30 | Hesperevax caulescens (Benth.) Gray | dwarf dwarf-cudweed | Asteraceae
|
| HESPB | Hesperevax sparsiflora (Gray) Greene var. brevifolia (Gray) Morefield | shortleaf dwarf-cudweed | Asteraceae
|
| HESPS2 | Hesperevax sparsiflora (Gray) Greene var. sparsiflora | erect dwarf-cudweed | Asteraceae
|
| HESP9 | Hesperevax sparsiflora (Gray) Greene | erect dwarf-cudweed | Asteraceae
|
| HESPE10 | Hesperevax (Gray) Gray | dwarf-cudweed | Asteraceae
|
| HELI6 | Hesperidanthus linearifolius (Gray) Rydb. | Schoenocrambe linearifolia | Brassicaceae
|
| HEMA3 | Hesperis matronalis L. | dames rocket | Brassicaceae
|
| HEPI8 | Hesperis pinnatifidus Michx. | Iodanthus pinnatifidus | Brassicaceae
|
| HESPE2 | Hesperis L. | rocket | Brassicaceae
|
| HEUN2 | Hesperocallis undulata Gray | desert lily | Liliaceae
|
| HESPE3 | Hesperocallis Gray | desert lily | Liliaceae
|
| HECAI | Hesperochiron californicus (Benth.) S. Wats. var. incanus (Greene) Brand | Hesperochiron californicus | Hydrophyllaceae
|
| HECAW | Hesperochiron californicus (Benth.) S. Wats. var. watsonianus (Greene) Brand | Hesperochiron californicus | Hydrophyllaceae
|
| HECA7 | Hesperochiron californicus (Benth.) S. Wats. | California hesperochiron | Hydrophyllaceae
|
| HELA14 | Hesperochiron lasianthus (Greene) St. John | Hesperochiron californicus | Hydrophyllaceae
|
| HEPU6 | Hesperochiron pumilus (Dougl. ex Griseb.) Porter | dwarf hesperochiron | Hydrophyllaceae
|
| HEVI8 | Hesperochiron villosulus (Greene) Suksdorf | Hesperochiron pumilus | Hydrophyllaceae
|
| HESPE4 | Hesperochiron S. Wats. | hesperochiron | Hydrophyllaceae
|
| HEKI | Hesperochloa kingii (S. Wats.) Rydb. | Leucopoa kingii | Poaceae
|
| HESA5 | Hesperocnide sandwicensis (Weddell) Weddell | Hawai'i stingingnettle | Urticaceae
|
| HETE5 | Hesperocnide tenella Torr. | western stingingnettle | Urticaceae
|
| HESPE6 | Hesperocnide Torr. | stingingnettle | Urticaceae
|
| HEHA3 | Hesperodoria hallii (Gray) Greene | Columbiadoria hallii | Asteraceae
|
| HESA13 | Hesperodoria salicina (Blake) Nesom | willow glowweed | Asteraceae
|
| HESC15 | Hesperodoria scopulorum (M.E. Jones) Greene | Grand Canyon glowweed | Asteraceae
|
| HESPE9 | Hesperodoria Greene | glowweed | Asteraceae
|
| HEST6 | Hesperogenia stricklandii Coult. & Rose | Tauschia stricklandii | Apiaceae
|
| HEAD | Hesperolinon adenophyllum (Gray) Small | glandular dwarf-flax | Linaceae
|
| HEBI3 | Hesperolinon bicarpellatum (H.K. Sharsmith) H.K. Sharsmith | twocarpel dwarf-flax | Linaceae
|
| HEBR4 | Hesperolinon breweri (Gray) Small | Brewer's dwarf-flax | Linaceae
|
| HECA11 | Hesperolinon californicum (Benth.) Small | California dwarf-flax | Linaceae
|
| HECL3 | Hesperolinon clevelandii (Greene) Small | Allen Springs dwarf-flax | Linaceae
|
| HECO12 | Hesperolinon congestum (Gray) Small | Marin dwarf-flax | Linaceae
|
| HEDI3 | Hesperolinon didymocarpum H.K. Sharsmith | Lake County dwarf-flax | Linaceae
|
| HEDI4 | Hesperolinon disjunctum H.K. Sharsmith | Coast Range dwarf-flax | Linaceae
|
| HEDR4 | Hesperolinon drymarioides (Curran) Small | drymary dwarf-flax | Linaceae
|
| HEMI9 | Hesperolinon micranthum (Gray) Small | smallflower dwarf-flax | Linaceae
|
| HESE8 | Hesperolinon serpentinum N. McCarten | Napa dwarf-flax | Linaceae
|
| HESP5 | Hesperolinon spergulinum (Gray) Small | slender dwarf-flax | Linaceae
|
| HETE8 | Hesperolinon tehamense H.K. Sharsmith | Paskenta Grade dwarf-flax | Linaceae
|
| HESPE7 | Hesperolinon (Gray) Small | dwarf-flax | Linaceae
|
| HEARB | Hesperomannia arborescens Gray var. bushiana (O. Deg.) Carlq. | Hesperomannia arborescens | Asteraceae
|
| HEARS | Hesperomannia arborescens Gray var. swezeyi (O. Deg.) Carlq. | Hesperomannia arborescens | Asteraceae
|
| HEAR9 | Hesperomannia arborescens Gray | Lanai island-aster | Asteraceae
|
| HEARO | Hesperomannia arbuscula Hbd. ssp. oahuensis (Hbd.) Carlq. | Hesperomannia arbuscula | Asteraceae
|
| HEARP | Hesperomannia arbuscula Hbd. var. pearsallii St. John | Hesperomannia arbuscula | Asteraceae
|
| HEAR10 | Hesperomannia arbuscula Hbd. | Maui island-aster | Asteraceae
|
| HELY | Hesperomannia lydgatei Forbes | Kauai island-aster | Asteraceae
|
| HEMA13 | Hesperomannia mauiensis St. John | Hesperomannia arbuscula | Asteraceae
|
| HESPE8 | Hesperomannia Gray | island-aster | Asteraceae
|
| HELI8 | Hesperomecon linearis (Benth.) Greene | Platystigma linearis | Papaveraceae
|
| HEAS3 | Hesperonia aspera (Greene) Standl. | Mirabilis bigelovii var. bigelovii | Nyctaginaceae
|
| HEBI6 | Hesperonia bigelovii (Gray) Standl. | Mirabilis bigelovii var. bigelovii | Nyctaginaceae
|
| HECE3 | Hesperonia cedrosensis Standl. | Mirabilis californica var. cedrosensis | Nyctaginaceae
|
| HETE12 | Hesperonia tenuiloba (S. Wats.) Standl. | Mirabilis tenuiloba | Nyctaginaceae
|
| HEMA16 | Hesperoscordium maritimum Torr. | Muilla maritima | Liliaceae
|
| HEHY3 | Hesperoscordum hyacinthinum Lindl. | Triteleia hyacinthina | Liliaceae
|
| HELI7 | Hesperoscordum lilacinum (Greene) Heller ex Abrams | Triteleia lilacinum | Liliaceae
|
| HECOC8 | Hesperostipa comata (Trin. & Rupr.) Barkworth ssp. comata | needle and thread | Poaceae
|
| HECOI | Hesperostipa comata (Trin. & Rupr.) Barkworth ssp. intermedia (Scribn. & Tweedy) Barkworth | intermediate needle and thread | Poaceae
|
| HECO26 | Hesperostipa comata (Trin. & Rupr.) Barkworth | needle and thread | Poaceae
|
| HECU9 | Hesperostipa curtiseta (A.S. Hitchc.) Barkworth | shortbristle needle and thread | Poaceae
|
| HENE5 | Hesperostipa neomexicana (Thurb. ex Coult.) Barkworth | New Mexico feathergrass | Poaceae
|
| HESP11 | Hesperostipa spartea (Trin.) Barkworth | porcupinegrass | Poaceae
|
| HESPE11 | Hesperostipa (Elias) Barkworth | needle and thread | Poaceae
|
| HETR9 | Hesperoxalis trilliifolia (Hook.) Small | Oxalis trilliifolia | Oxalidaceae
|
| HEWH | Hesperoyucca whipplei (Torr.) Baker | Yucca whipplei var. whipplei | Agavaceae
|
| HEVI12 | Heteranthemis viscidehirta Schott | sticky oxeye | Asteraceae
|
| HETER18 | Heteranthemis Schott | oxeye | Asteraceae
|
| HEDU2 | Heteranthera dubia (Jacq.) MacM. | grassleaf mudplantain | Pontederiaceae
|
| HEGR13 | Heteranthera graminea (Michx.) Vahl | Heteranthera dubia | Pontederiaceae
|
| HELI3 | Heteranthera liebmannii (Buch. ex Magnus) Shinners | Heteranthera dubia | Pontederiaceae
|
| HELI2 | Heteranthera limosa (Sw.) Willd. | blue mudplantain | Pontederiaceae
|
| HEME6 | Heteranthera mexicana S. Wats. | Mexican mudplantain | Pontederiaceae
|
| HEMU5 | Heteranthera multiflora (Griseb.) Horn | bouquet mudplantain | Pontederiaceae
|
| HEPE3 | Heteranthera peduncularis Benth. | egret mudplantain | Pontederiaceae
|
| HEREM | Heteranthera reniformis Ruiz & Pavón var. multiflora Griseb. | Heteranthera multiflora | Pontederiaceae
|
| HERE | Heteranthera reniformis Ruiz & Pavón | kidneyleaf mudplantain | Pontederiaceae
|
| HERO5 | Heteranthera rotundifolia (Kunth) Griseb. | roundleaf mudplantain | Pontederiaceae
|
| HETER | Heteranthera Ruiz & Pavón | mudplantain | Pontederiaceae
|
| HEOC5 | Heterocarpon ochroleucum (Tuck.) Mull. Arg. | | Verrucariaceae
|