| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| HOMA | Holocarpha macradenia (DC.) Greene | Santa Cruz tarplant | Asteraceae
|
| HOOBA | Holocarpha obconica (J.C. Clausen & Keck) Keck ssp. autumnalis Keck | San Joaquin tarweed | Asteraceae
|
| HOOBO | Holocarpha obconica (J.C. Clausen & Keck) Keck ssp. obconica | San Joaquin tarweed | Asteraceae
|
| HOOB | Holocarpha obconica (J.C. Clausen & Keck) Keck | San Joaquin tarweed | Asteraceae
|
| HOVIE | Holocarpha virgata (Gray) Keck ssp. elongata Keck | wand tarbush | Asteraceae
|
| HOVIV | Holocarpha virgata (Gray) Keck ssp. virgata | yellowflower tarweed | Asteraceae
|
| HOVI | Holocarpha virgata (Gray) Keck | yellowflower tarweed | Asteraceae
|
| HOLOC | Holocarpha Greene | tarweed | Asteraceae
|
| HOBO | Holodiscus boursieri (Carr.) Rehd. | Holodiscus discolor | Rosaceae
|
| HODIF2 | Holodiscus discolor (Pursh) Maxim. ssp. franciscanus (Rydb.) Taylor & MacBryde | Holodiscus discolor | Rosaceae
|
| HODID | Holodiscus discolor (Pursh) Maxim. var. delnortensis Ley | Holodiscus discolor | Rosaceae
|
| HODID2 | Holodiscus discolor (Pursh) Maxim. var. dumosus (Nutt. ex Hook.) Maxim. ex Coult. | Holodiscus dumosus | Rosaceae
|
| HODIF | Holodiscus discolor (Pursh) Maxim. var. franciscanus (Rydb.) Jepson | Holodiscus discolor | Rosaceae
|
| HODIG | Holodiscus discolor (Pursh) Maxim. var. glabrescens (Greenm.) Jepson | Holodiscus discolor | Rosaceae
|
| HODI | Holodiscus discolor (Pursh) Maxim. | oceanspray | Rosaceae
|
| HODUS | Holodiscus dumosus (Nutt. ex Hook.) Heller ssp. saxicola (Heller) Abrams | Holodiscus discolor | Rosaceae
|
| HODUA | Holodiscus dumosus (Nutt. ex Hook.) Heller var. australis (Heller) Ley | Holodiscus discolor | Rosaceae
|
| HODUG2 | Holodiscus dumosus (Nutt. ex Hook.) Heller var. glabrescens (Greenm.) C.L. Hichc. | Holodiscus discolor | Rosaceae
|
| HODUT | Holodiscus dumosus (Nutt. ex Hook.) Heller var. typicus Ley | Holodiscus dumosus | Rosaceae
|
| HODU | Holodiscus dumosus (Nutt. ex Hook.) Heller | rockspirea | Rosaceae
|
| HOGL4 | Holodiscus glabrescens (Greenm.) Heller | Holodiscus discolor | Rosaceae
|
| HOMIG | Holodiscus microphyllus Rydb. var. glabrescens (Greenm.) Ley | Holodiscus discolor | Rosaceae
|
| HOMIS | Holodiscus microphyllus Rydb. var. sericeus Ley | Holodiscus discolor | Rosaceae
|
| HOMIT | Holodiscus microphyllus Rydb. var. typicus Ley | Holodiscus discolor | Rosaceae
|
| HOMI3 | Holodiscus microphyllus Rydb. | Holodiscus discolor | Rosaceae
|
| HOLOD | Holodiscus (K. Koch) Maxim. | oceanspray | Rosaceae
|
| HOVU2 | Holoschoenus vulgaris Link | Scirpoides holoschoenus | Cyperaceae
|
| HOUM | Holosteum umbellatum L. | jagged chickweed | Caryophyllaceae
|
| HOLOS | Holosteum L. | holosteum | Caryophyllaceae
|
| HOFI | Holozonia filipes (Hook. & Arn.) Greene | whitecrown | Asteraceae
|
| HOLOZ | Holozonia Greene | holozonia | Asteraceae
|
| HOGR4 | Homalia gracilis James in Peck | Homalia trichomanoides | Neckeraceae
|
| HOJAG | Homalia jamesii Schimp. var. gracilis (James in Peck) Wagn. | Homalia trichomanoides | Neckeraceae
|
| HOJA4 | Homalia jamesii Schimp. | Homalia trichomanoides | Neckeraceae
|
| HOSH2 | Homalia sharpii Williams | Homaliadelphus sharpii | Neckeraceae
|
| HOTR4 | Homalia trichomanoides (Hedw.) Schimp. in B.S.G. | homalia moss | Neckeraceae
|
| HOMAL3 | Homalia (Brid.) Schimp. in B.S.G. | homalia moss | Neckeraceae
|
| HOSH | Homaliadelphus sharpii (Williams) Sharp | Sharp's homaliadelphus moss | Neckeraceae
|
| HOMAL7 | Homaliadelphus Dix. & P. Varde in Dix. | homaliadelphus moss | Neckeraceae
|
| HOLE3 | Homalium leiogynum Blake | Homalium racemosum | Flacourtiaceae
|
| HOPL3 | Homalium pleiandrum Blake | Homalium racemosum | Flacourtiaceae
|
| HORA | Homalium racemosum Jacq. | white cogwood | Flacourtiaceae
|
| HOMAL | Homalium Jacq. | homalium | Flacourtiaceae
|
| HOCA7 | Homalobus caespitosus Nutt. | Astragalus spatulatus | Fabaceae
|
| HOCA11 | Homalobus campestris Nutt. | Astragalus conjunctus var. conjunctus | Fabaceae
|
| HOTE5 | Homalobus tenellus (Pursh) Britt. | Astragalus tenellus | Fabaceae
|
| HOVE2 | Homalobus vexilliflexus (Sheldon) Rydb. | Astragalus vexilliflexus var. vexilliflexus | Fabaceae
|
| HOHE4 | Homalocenchrus hexandrus (Sw.) Kuntze | Leersia hexandra | Poaceae
|
| HOLE5 | Homalocenchrus lenticularis (Michx.) Kuntze | Leersia lenticularis | Poaceae
|
| HOMO4 | Homalocenchrus monandrus (Sw.) Kuntze | Leersia monandra | Poaceae
|
| HOOR3 | Homalocenchrus oryzoides (L.) Pollich | Leersia oryzoides | Poaceae
|
| HOVI4 | Homalocenchrus virginicus (Willd.) Britt. | Leersia virginica | Poaceae
|
| HOTE7 | Homalocephala texensis (Hopffer) Britt. & Rose | Echinocactus texensis | Cactaceae
|
| HOPL5 | Homalocladium platycladum (F.J. Muell.) Bailey | ribbonbush | Polygonaceae
|
| HOMAL2 | Homalocladium (F.J. Muell.) Bailey | homalocladium | Polygonaceae
|
| HOFA4 | Homalotheciella fabrofolia [fabronifolia] (Grout) Broth. | Homalotheciella subcapillata | Brachytheciaceae
|
| HOSU4 | Homalotheciella subcapillata (Hedw.) Broth. | homalotheciella moss | Brachytheciaceae
|
| HOMAL4 | Homalotheciella (Card.) Broth. | homalotheciella moss | Brachytheciaceae
|
| HOAE2 | Homalothecium aeneum (Mitt.) Lawt. | bright copper homalothecium moss | Brachytheciaceae
|
| HOAR4 | Homalothecium arenarium (Lesq.) Lawt. | sandwort homalothecium moss | Brachytheciaceae
|
| HOBO4 | Homalothecium bonplandii Jaeg. | Palamocladium leskeoides | Brachytheciaceae
|
| HOFU70 | Homalothecium fulgescens (Mitt. ex C. M�ll.) Lawt. | tree mat homalothecium moss | Brachytheciaceae
|
| HOLE6 | Homalothecium leskeoides (Hook.) Robins. | Palamocladium leskeoides | Brachytheciaceae
|
| HOME3 | Homalothecium megaptilum (Sull.) Robins. | Trachybryum megaptilum | Brachytheciaceae
|
| HONES | Homalothecium nevadense (Lesq.) Ren. & Card. var. subulatum Ren. & Card. in R�ll | Homalothecium nevadense | Brachytheciaceae
|
| HONE3 | Homalothecium nevadense (Lesq.) Ren. & Card. | Nevada homalothecium moss | Brachytheciaceae
|
| HONI3 | Homalothecium nitens (Hedw.) Robins. | Tomentypnum nitens | Brachytheciaceae
|
| HONUH | Homalothecium nuttallii (Wils.) Jaeg. var. hamatidens (Kindb.) Grout | Homalothecium nuttallii | Brachytheciaceae
|
| HONUS | Homalothecium nuttallii (Wils.) Jaeg. var. stoloniferum (Lesq.) L. Koch | Homalothecium nuttallii | Brachytheciaceae
|
| HONUT | Homalothecium nuttallii (Wils.) Jaeg. var. tenue (Kindb.) Grout | Homalothecium nuttallii | Brachytheciaceae
|
| HONU | Homalothecium nuttallii (Wils.) Jaeg. | Nuttall's homalothecium moss | Brachytheciaceae
|
| HOPI2 | Homalothecium pinnatifidum (Sull. & Lesq.) Lawt. | pinnatifid homalothecium moss | Brachytheciaceae
|
| HOSE5 | Homalothecium sericeum (Hedw.) Schimp. in B.S.G. | silken homalothecium moss | Brachytheciaceae
|
| HOMAL5 | Homalothecium Schimp. in B.S.G. | homalothecium moss | Brachytheciaceae
|
| HOCO6 | Homeria collina (Thunb.) Salisb. | Cape tulip | Iridaceae
|
| HOMER | Homeria Vent. | Cape tulip | Iridaceae
|
| HOADN | Homomallium adnatum (Hedw.) Broth. var. nelsonii Kindb. ex Gier | Homomallium adnatum | Hypnaceae
|
| HOAD | Homomallium adnatum (Hedw.) Broth. | homomallium moss | Hypnaceae
|
| HOIN5 | Homomallium incurvatum (Brid.) Loeske | homomallium moss | Hypnaceae
|
| HOMEL | Homomallium mexicanum Card. var. latifolium Card. | wideleaf homomallium moss | Hypnaceae
|
| HOMEM | Homomallium mexicanum Card. var. mexicanum | Mexican homomallium moss | Hypnaceae
|
| HOME4 | Homomallium mexicanum Card. | Mexican homomallium moss | Hypnaceae
|
| HOMOM | Homomallium (Schimp.) Loeske | homomallium moss | Hypnaceae
|
| HOPI3 | Homostegia piggotii (Berk. & Broome) P. Karst. | | Uncertain Lichen Family
|
| HOMOS | Homostegia Fuckel | homostegia | Uncertain Lichen Family
|
| HODI4 | Honckenya diffusa (Hornem.) A.& D. L�ve | Honckenya peploides ssp. diffusa | Caryophyllaceae
|
| HOOB3 | Honckenya oblongifolia Torr. & Gray | Honckenya peploides ssp. major | Caryophyllaceae
|
| HOPED | Honckenya peploides (L.) Ehrh. ssp. diffusa (Hornem.) Hult�n | seaside sandplant | Caryophyllaceae
|
| HOPEM2 | Honckenya peploides (L.) Ehrh. ssp. major (Hook.) Hult�n | seaside sandplant | Caryophyllaceae
|
| HOPER2 | Honckenya peploides (L.) Ehrh. ssp. robusta (Fern.) Hult�n | seaside sandplant | Caryophyllaceae
|
| HOPEM4 | Honckenya peploides (L.) Ehrh. var. major (Hook.) Abrams | Honckenya peploides ssp. major | Caryophyllaceae
|
| HOPER4 | Honckenya peploides (L.) Ehrh. var. robusta (Fern.) House | Honckenya peploides ssp. robusta | Caryophyllaceae
|
| HOPE | Honckenya peploides (L.) Ehrh. | seaside sandplant | Caryophyllaceae
|
| HONCK | Honckenya Ehrh. | honckenya | Caryophyllaceae
|
| HOAC2 | Hookeria acutifolia Hook. & Grev. | sharpleaf hookeria moss | Hookeriaceae
|
| HOFI4 | Hookeria filifolia (S. Wats.) Greene | Brodiaea filifolia | Liliaceae
|
| HOLE4 | Hookeria leptandra Greene | Brodiaea californica var. leptandra | Liliaceae
|
| HOLU | Hookeria lucens (Hedw.) Sm. | hookeria moss | Hookeriaceae
|
| HOMI7 | Hookeria minor (Benth.) Kunze | Brodiaea minor | Liliaceae
|
| HOOR2 | Hookeria orcuttii Greene | Brodiaea orcuttii | Liliaceae
|
| HOPA8 | Hookeria pallida Hornsch. | Callicostella pallida | Callicostaceae
|