| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| HAVI6 | Harperella vivipara Rose | Ptilimnium nodosum | Apiaceae
|
| HAFL3 | Harperocallis flava McDaniel | Harper's beauty | Liliaceae
|
| HARPE | Harperocallis McDaniel | harperocallis | Liliaceae
|
| HAAR4 | Harpullia arborea (Blanco) Radlk. | | Sapindaceae
|
| HARPU | Harpullia Roxb. | harpullia | Sapindaceae
|
| HAHY2 | Harrimanella hypnoides (L.) Coville | mossplant | Ericaceae
|
| HAST3 | Harrimanella stelleriana (Pallas) Coville | Alaska bellheather | Ericaceae
|
| HARRI3 | Harrimanella Coville | harrimanella | Ericaceae
|
| HAFI | Harrisella filiformis (Sw.) Cogn. | Campylocentrum filiforme | Orchidaceae
|
| HAPO | Harrisella porrecta (Reichenb. f.) Fawcett & Rendle | needleroot airplant orchid | Orchidaceae
|
| HARRI | Harrisella Fawcett & Rendle | harrisella | Orchidaceae
|
| HAAB2 | Harrisia aboriginum Small | prickly applecactus | Cactaceae
|
| HABO | Harrisia bonplandii (Parmentier) Britt. & Rose | Harrisia pomanensis | Cactaceae
|
| HAFR3 | Harrisia fragrans Small | Caribbean applecactus | Cactaceae
|
| HAMA7 | Harrisia martinii (Labouret) Britt. | mooncactus | Cactaceae
|
| HAPO6 | Harrisia pomanensis Weber | applecactus | Cactaceae
|
| HAPO2 | Harrisia portoricensis Britt. | Puerto Rico applecactus | Cactaceae
|
| HASI | Harrisia simpsonii Small | Simpson's applecactus | Cactaceae
|
| HARRI2 | Harrisia Britt. | applecactus | Cactaceae
|
| HASP4 | Hartmannia speciosa (Nutt.) Small | Oenothera speciosa | Onagraceae
|
| HAFL4 | Hartwrightia floridana Gray ex S. Wats. | Florida hartwrightia | Asteraceae
|
| HARTW | Hartwrightia Gray ex S. Wats. | hartwrightia | Asteraceae
|
| HABA3 | Hassea bacillosa (Nyl.) Zahlbr. | | Uncertain Lichen Family
|
| HASSE | Hassea Zahlbr. | hassea | Uncertain Lichen Family
|
| HABL4 | Hasseanthus blochmaniae (Eastw.) Rose | Dudleya blochmaniae ssp. blochmaniae | Crassulaceae
|
| HAEL3 | Hasseanthus elongatus Rose | Dudleya multicaulis | Crassulaceae
|
| HAVA2 | Hasseanthus variegatus (S. Wats.) Rose | Dudleya variegata | Crassulaceae
|
| HARO | Hasteola robertiorum L.C. Anders. | hammockherb | Asteraceae
|
| HASU3 | Hasteola suaveolens (L.) Pojark. | false Indian plaintain | Asteraceae
|
| HASTE2 | Hasteola Raf. | false Indian plaintain | Asteraceae
|
| HAAL2 | Hastingsia alba (Dur.) S. Wats. | white rushlily | Liliaceae
|
| HAAT | Hastingsia atropurpurea Becking | Hastingsia bracteosa var. atropurpurea | Liliaceae
|
| HABRA2 | Hastingsia bracteosa S. Wats. var. atropurpurea (Becking) F. Lang & P. Zika | purple rushlily | Liliaceae
|
| HABRB | Hastingsia bracteosa S. Wats. var. bracteosa | largeflower rushlily | Liliaceae
|
| HABR5 | Hastingsia bracteosa S. Wats. | largeflower rushlily | Liliaceae
|
| HASE2 | Hastingsia serpenticola Becking | Klamath rushlily | Liliaceae
|
| HASTI | Hastingsia S. Wats. | rushlily | Liliaceae
|
| HAGA | Hatiora gaertneri (Regel) Barthlott | Easter cactus | Cactaceae
|
| HATIO | Hatiora Britton & Rose | hatiora | Cactaceae
|
| HAPA10 | Havardia pallens (Benth.) Britt. & Rose | haujillo | Fabaceae
|
| HAVAR | Havardia Small | havardia | Fabaceae
|
| HAPE5 | Hawksworthiana peltigericola (D. Hawksw.) U. Braun | Hawksworth's lichen | Uncertain Lichen Family
|
| HAWKS | Hawksworthiana U. Braun | Hawksworth's lichen | Uncertain Lichen Family
|
| HAVI5 | Haynaldia villosa (L.) Schur | Dasypyrum villosum | Poaceae
|
| HABR3 | Hazardia brickellioides (Blake) W.D. Clark | brickellbush goldenweed | Asteraceae
|
| HACA6 | Hazardia cana (Gray) Greene | island hazardia | Asteraceae
|
| HADE4 | Hazardia detonsa (Greene) Greene | island bristleweed | Asteraceae
|
| HAOR3 | Hazardia orcuttii (Gray) Greene | Orcutt's bristleweed | Asteraceae
|
| HASQG2 | Hazardia squarrosa (Hook. & Arn.) Greene var. grindelioides (DC.) W.D. Clark | sawtooth bristleweed | Asteraceae
|
| HASQO2 | Hazardia squarrosa (Hook. & Arn.) Greene var. obtusa (Greene) Jepson | sawtooth bristleweed | Asteraceae
|
| HASQS2 | Hazardia squarrosa (Hook. & Arn.) Greene var. squarrosa | sawtooth goldenbush | Asteraceae
|
| HASQ2 | Hazardia squarrosa (Hook. & Arn.) Greene | sawtooth goldenbush | Asteraceae
|
| HAST4 | Hazardia stenolepis (Hall) Hoover | serpentine bristleweed | Asteraceae
|
| HAWHD2 | Hazardia whitneyi (Gray) Greene var. discoidea (J.T. Howell) W.D. Clark | Whitney's bristleweed | Asteraceae
|
| HAWHW | Hazardia whitneyi (Gray) Greene var. whitneyi | Whitney's bristleweed | Asteraceae
|
| HAWH3 | Hazardia whitneyi (Gray) Greene | Whitney's bristleweed | Asteraceae
|
| HAZAR | Hazardia Greene | bristleweed | Asteraceae
|
| HEPA16 | Hebanthe palmeri S. Wats. | Iresine palmeri | Amaranthaceae
|
| HEFR | Hebe �franciscana (Eastw.) Souster | | Scrophulariaceae
|
| HESP | Hebe speciosa (R. Cunningham ex A. Cunningham) J.C. Andersen | New Zealand hebe | Scrophulariaceae
|
| HEVE7 | Hebe venustula (Colenso) Cockayne | | Scrophulariaceae
|
| HEBE | Hebe Comm. ex Juss. | hebe | Scrophulariaceae
|
| HEMA9 | Hebeclinium macrophyllum (L.) DC. | largeleaf thoroughwort | Asteraceae
|
| HEBEC2 | Hebeclinium DC. | thoroughwort | Asteraceae
|
| HESH | Hecastocleis shockleyi Gray | prickleleaf | Asteraceae
|
| HECAS | Hecastocleis Gray | hecastocleis | Asteraceae
|
| HESC9 | Hecatonia scelerata (L.) Fourr. | Ranunculus sceleratus var. sceleratus | Ranunculaceae
|
| HEGL7 | Hechtia glomerata Zucc. | guapilla | Bromeliaceae
|
| HESC4 | Hechtia scariosa L.B. Sm. | Hechtia texensis | Bromeliaceae
|
| HETE7 | Hechtia texensis S. Wats. | Texas false agave | Bromeliaceae
|
| HECHT | Hechtia Klotzsch | hechtia | Bromeliaceae
|
| HEPU8 | Hecistopteris pumila (Spreng.) J. Sm. | moss fern | Vittariaceae
|
| HECIS | Hecistopteris J. Sm. | hecistopteris | Vittariaceae
|
| HEAC | Hedeoma acinoides Scheele | slender false pennyroyal | Lamiaceae
|
| HEAN13 | Hedeoma angulata Tharp | Rhododon angulatus | Lamiaceae
|
| HEAP | Hedeoma apiculata W.S. Stewart | McKittrick's false pennyroyal | Lamiaceae
|
| HEAR13 | Hedeoma arkansana Nutt. | Clinopodium arkansanum | Lamiaceae
|
| HEBL | Hedeoma blepharodonta Greene | Hedeoma diffusa | Lamiaceae
|
| HECA18 | Hedeoma campora Rydb. | Hedeoma drummondii | Lamiaceae
|
| HECI6 | Hedeoma ciliata Benth. | Rhododon ciliatus | Lamiaceae
|
| HECI8 | Hedeoma ciliata Nutt. | Hedeoma drummondii | Lamiaceae
|
| HECO21 | Hedeoma convisae A. Nels. | Hedeoma costata var. pulchella | Lamiaceae
|
| HECOC4 | Hedeoma costata Gray var. costata | ribbed false pennyroyal | Lamiaceae
|
| HECOP | Hedeoma costata Gray var. pulchella (Greene) Irving | ribbed false pennyroyal | Lamiaceae
|
| HECO | Hedeoma costata Gray | ribbed false pennyroyal | Lamiaceae
|
| HEDE2 | Hedeoma dentata Torr. | dentate false pennyroyal | Lamiaceae
|
| HEDI | Hedeoma diffusa Greene | spreading false pennyroyal | Lamiaceae
|
| HEDRC | Hedeoma drummondii Benth. var. crenulata Irving | Hedeoma drummondii | Lamiaceae
|
| HEDRR | Hedeoma drummondii Benth. var. reverchonii Gray | Hedeoma reverchonii var. reverchonii | Lamiaceae
|
| HEDR | Hedeoma drummondii Benth. | Drummond's false pennyroyal | Lamiaceae
|
| HEGL11 | Hedeoma glabra Nutt. | Clinopodium arkansanum | Lamiaceae
|
| HEGL12 | Hedeoma glabrescens (Gray) Briq. | Poliomintha glabrescens | Lamiaceae
|
| HEGR12 | Hedeoma graveolens Chapman ex Gray | Stachydeoma graveolens | Lamiaceae
|
| HEHI | Hedeoma hispida Pursh | rough false pennyroyal | Lamiaceae
|
| HEHY | Hedeoma hyssopifolia Gray | aromatic false pennyroyal | Lamiaceae
|
| HEIN11 | Hedeoma incana Torr. | Poliomintha incana | Lamiaceae
|
| HELA15 | Hedeoma lata Small | Hedeoma reverchonii var. reverchonii | Lamiaceae
|
| HELO9 | Hedeoma longiflora Rydb. | Hedeoma drummondii | Lamiaceae
|
| HEMO | Hedeoma mollis Torr. | softhair false pennyroyal | Lamiaceae
|
| HENAC | Hedeoma nana (Torr.) Briq. ssp. californica W.S. Stewart | California false pennyroyal | Lamiaceae
|
| HENAM | Hedeoma nana (Torr.) Briq. ssp. macrocalyx W.S. Stewart | dwarf false pennyroyal | Lamiaceae
|