Hackberry, Western (Celtis reticulata)
Hairgrass, Slender (Deschampsia elongata)
Hairy blazing star (Mentzelia hirsutissima)
Hairy blue sage (Salvia dorrii var. pilosa)
Hairy bush monkeyflower (Diplacus longiflorus)
Hairy ceanothus (Ceanothus oliganthus var. oliganthus)
Hairy evening primrose (Oenothera elata ssp. hirsutissima)
Hairy goldenheads (Acamptopappus sphaerocephalus var. hirtellus)
Hairy gumplant (Grindelia hirsutula)
Hairy honeysuckle (Lonicera hispidula)
Hairy-leaved pectocarya (Pectocarya heterocarpa)
Hairy milkweed (Funastrum hirtellum)
Hairy owl's clover (Castilleja tenuis)
Hairypink (Petrorhagia dubia)*
Hairy-podded peppergrass (Lepidium lasiocarpum ssp. lasiocarpum)
Hairy sand-spurrey (Spergularia villosa)*
Hairy sun cup (Camissoniopsis hirtella)
Hairy windmills (Allionia incarnata var. villosa)
Hairy winter vetch (Vicia villosa ssp. villosa)*
Hairy wood rush (Luzula comosa)
Hairy yerba santa (Eriodictyon trichocalyx var. trichocalyx)
Hall's brome (Bromus hallii)
Hall's bush lupine (Lupinus albifrons var. hallii)
Hall's caulanthus (Caulanthus hallii)
Hall's tetracoccus (Tetracoccus hallii)
Hall's willow-herb (Epilobium hallianum)
Hansen's spike-moss (Selaginella hansenii)
Harding grass (Phalaris aquatica)*
Hare barley (Hordeum murinum ssp. leporinum)*
Hareleaf, Branched (Lagophylla ramosissima)
Harlequin lupine (Lupinus stiversii)
Harsh popcorn flower (Plagiobothrys hispidulus)
Hartweg's iris (Iris hartwegii ssp. australis)
Harvest brodiaea (Brodiaea elegans ssp. elegans)
Harwood's woolstar (Eriastrum harwoodii)
Hasse's dudleya (Dudleya virens ssp. hassei)
Hawksbeard,
    Dwarf (Crepis nana)
    Tall (Crepis acuminata)
    Western (Crepis occidentalis)
Hawkweed,
    [Common] (Hieracium argutum)
    Shaggy (Hieracium horridum)
    White-flowered (Hieracium albiflorum)
Hawkweed layia (Layia hieracioides)
Hazardia,
    Holly-leaved (Hazardia brickellioides)
    Island (Hazardia detonsa)
    Orcutt's (Hazardia orcuttii)
Heartleaf jewelflower (Streptanthus cordatus var. cordatus)
Heartleaf penstemon (Keckiella cordifolia)
Heartleaf pitcher sage (Lepechinia cardiophylla)
Heartleaf sun cup (Chylismia cardiophylla ssp. cardiophylla)
Heartleaf thornmint (Acanthomintha obovata ssp. cordata)
Heath,
    Alkali (Frankenia salina)
    Rose (Chaetopappa ericoides)
Heather,
    Mock (Ericameria ericoides)
    Mountain (Phyllodoce breweri)
Heckard's paintbrush (Castilleja montigena)
Hedge mustard (Sisymbrium officinale)*
Hedge-nettle,
    California (Stachys bullata)
    Rigid (Stachys rigida)
    White (Stachys albens)
Hedge-parsley,
    California (Yabea microcarpa)
    [Common] (Torilis nodosa)*
    Field (Torilis arvensis)*
Heermann's buckwheat (Eriogonum heermannii var. argense)
Heermann's buckwheat, Large (Eriogonum heermannii var. heermannii)
Heermann's lotus (Acmispon heermannii var. heermannii)
Heermann's tarplant (Holocarpha heermannii)
Heliotrope, Wild (Heliotropium curassavicum var. oculatum)
Hemlock, Poison (Conium maculatum)*
Hemp dogbane (Apocynum cannabinum)
Henbit (Lamium amplexicaule)*
Herb sophia, see Flix weed
Herniaria, Gray (Herniaria hirsuta var. cinerea)*
Heron's bill, Desert (Erodium texanum)
Hesperochiron, California (Hesperochiron nanus)
Heterocodon, Few-flowered (Heterocodon rariflorum)
Hibiscus, Rock (Hibiscus denudatus)
Hiddenflower phacelia (Phacelia cryptantha)
Hidden lake bluecurls (Trichostema austromontanum ssp. compactum)
Hikers' gentian (Gentianopsis simplex)
Hilend's bedstraw (Galium hilendiae ssp. hilendiae)
Hill lotus (Acmispon brachycarpus)
Hillside gooseberry (Ribes californicum var. hesperium)
Hillside woodland star (Lithophragma heterophyllum)
Himalaya-berry (Rubus armeniacus)*
Himalayan smartweed (Persicaria capitata)*
Hinds' narrowleaf willow (Salix exigua var. hindsiana)
Hoary-aster,
    [Common] (Dieteria canescens var. canescens)
    Desert (Dieteria canescens var. leucanthemifolia)
Hoary coffeeberry,
    [Common] (Frangula californica ssp. tomentella)
    Sierra (Frangula californica ssp. cuspidata)
Hoary fuchsia (Epilobium canum ssp. canum)
Hoaryleaf ceanothus (Ceanothus crassifolius var. crassifolius)
Hoary nettle (Urtica dioica ssp. holosericea)
Hoffmannseggia (Hoffmannseggia microphylla)
Hogbite (Chondrilla juncea)*
Hog fennel (Lomatium utriculatum)
Hog potato (Hoffmannseggia glauca)
Hole-in-the-sand plant (Nicolletia occidentalis)
Holly,
    Creeping grape (Berberis aquifolium var. repens)
    Desert- (Atriplex hymenelytra)
    Summer (Comarostaphylis diversifolia ssp. diversifolia)
    Summer (Comarostaphylis diversifolia ssp. planifolia)
Hollyleaf cherry (Prunus ilicifolia ssp. ilicifolia)
Hollyleaf navarretia (Navarretia atractyloides)
Hollyleaf redberry (Rhamnus ilicifolia)
Holly-leaved bur-sage (Ambrosia ilicifolia)
Holly-leaved hazardia (Hazardia brickellioides)
Holly-leaved tetracoccus (Tetracoccus ilicifolius)
Honey mesquite (Prosopis glandulosa var. torreyana)
Honeysuckle,
    Chaparral (Lonicera interrupta)
    Hairy (Lonicera hispidula)
    Southern (Lonicera subspicata var. denudata)
Honeysweet (Tidestromia suffruticosa var. oblongifolia)
Hooked navarretia (Navarettia hamata ssp. hamata)
Hooked popcorn flower (Plagiobothrys undulatus)
Hooker's evening primrose (Oenothera elata ssp. hookeri)
Hopsage, Spiny (Grayia spinosa)
Hop tree (Ptelea crenulata)
Horehound (Marrubium vulgare)*
Horkelia,
    Barton Flats (Horkelia wilderae)
    Cleveland's (Horkelia clevelandii var. clevelandii)
    Ramona (Horkelia truncata)
    Rydberg's (Horkelia rydbergii)
    Wedge-leaf (Horkelia cuneata var. cuneata)
    White Mountains (Horkelia hispidula)
Horsebrush,
    Longspine (Tetradymia axillaris var. longispina)
    Spineless (Tetradymia canescens)
    Striped (Tetradymia argyraea)
Horse-nettle, Silverleaf (Solanum elaeagnifolium)*
Horsetail,
    Common (Equisetum arvense)
    Giant (Equisetum telmateia ssp. braunii)
Horseweed,
    Coulter's (Laennecia coulteri)
    Small (Erigeron bonariensis)*
    Tall (Erigeron canadensis)
Hottentot fig (Carpobrotus edulis)*
Hound's tongue, Grand (Cynoglossum grande)
Hubby's phacelia (Phacelia cicutaria var. hubbyi)
Huckleberry, California (Vaccinum ovatum)
Hulsea,
    Alpine gold (Hulsea algida)
    Beautiful (Hulsea vestita ssp. callicarpha)
    Parry's (Hulsea vestita ssp. parryi)
    Pygmy (Hulsea vestita ssp. pygmaea)
    Red-rayed (Hulsea heterochroma)
    San Diego (Hulsea californica)
    San Gabriel Mountains (Hulsea vestita ssp. gabrielensis)
Humboldt lily (Lilium humboldtii ssp. ocellatum)
Hutchinsia, Prostrate (Hornungia procumbens)
Hymenoxys, Arizona (Tetraneuris acaulis var. arizonica)
Hyssop, Giant (Agastache urticifolia)
Hyssop loosestrife (Lythrum hyssopifolia)
Iceplant,
    Crystalline (Mesembryanthemum crystallinum)*
    Red (Malephora crocea)*
    Slender-leaved (Mesembryanthemum nodiflorum)*
Idaho bentgrass (Agrostis idahoensis)
Idaho blue-eyed grass (Sisyrinchium idahoense var. occidentale)
Imbricate phacelia (Phacelia imbricata var. patula)
Incense-cedar (Calocedrus decurrens)
Indian breadroot, see California breadroot
Indian clover, see Rancheria clover
Indian hemp, see Hemp dogbane
Indian mallow, see Palmer's mallow
Indian milkweed, see Woolly-fruited milkweed
Indian paintbrush,
    Desert, see Desert paintbrush
    Frosted, see Mount Gleason paintbrush
    Heckard's, see Heckard's paintbrush
    Lesser, see Lesser paintbrush
    Longleaf, see longleaf paintbrush
    Soft-leaved, see Softleaved paintbrush
    Woolly, see Woolly paintbrush
Indian ricegrass, see Sand ricegrass
Indian rushpea, see Hog potato
Indian springparsley, see Spring-parsley
Indian tobacco, see Four-valved tobacco
Indian warrior, see Warrior's plume
Indigo bush,
    California (Psorothamnus arborescens var. simplicifolius)
    Dotted (Psorothamnus polydenius)
    Emory (Psorothamnus emoryi)
    Little-leaved Mojave (Psorothamnus arborescens var. minutifolius)
    Schott's (Psorothamnus schottii)
Inflated cima milkvetch (Astragalus cimae var. sufflatus)
Inland scrub oak (Quercus berberidifolia)
Inland sticky cinquefoil (Drymocallis glandulosa var. glandulosa)
Interior goldenbush (Ericameria linearifolia)
Interior live oak,
    [Common] (Quercus wislizeni var. wislizeni)
    Shrubby (Quercus wislizeni var. frutescens)
Interior manzanita (Arctostaphylos parryana ssp. tumescens)
Interior rose (Rosa woodsii ssp. gratissima)
Intermediate mariposa lily (Calochortus weedii var. intermedius)
Intermediate sun cup (Camissoniopsis intermedia)
Intermediate wheat grass (Elymus hispidus)*
Inyo blazing star (Mentzelia oreophila)
Inyo frasera (Frasera puberulenta)
Iodine bush (Allenrolfea occidentalis)
Ipomopsis,
    Arizona (Ipomopsis arizonica)
    Ballhead (Ipomopsis congesta ssp. montana)
Iris,
    Douglas's (Iris douglasiana)
    Hartweg's (Iris hartwegii ssp. australis)
Iris-leaved rush (Juncus xiphioides)
Ironwood,
    Desert (Olneya tesota)
    Fernleaf (Lyonothamnus floribundus ssp. aspleniifolius)
    Santa Catalina Island (Lyonothamnus floribundus ssp. floribundus)
Island alumroot (Heuchera maxima)
Island buckwheat (Eriogonum grande var. grande)
Island bush monkeyflower (Diplacus parviflorus)
Island ceanothus (Ceanothus arboreus)
Island checkerbloom (Sidalcea malviflora ssp. malviflora)
Island deerweed (Acmispon dendroideus var. dendroideus)
Island hazardia (Hazardia detonsa)
Island leafy bedstraw (Galium angustifolium ssp. foliosum)
Island mallow (Malva assurgentiflora)
Island manzanita (Arctostaphylos insularis)
Island mountain-mahogany (Cercocarpus betuloides var. blancheae)
Island oak (Quercus tomentella)
Island paintbrush (Castilleja hololeuca)
Island redberry (Rhamnus pirifolia)
Island sagebrush (Artemisia nesiotica)
Island shooting star (Primula clevelandii ssp. insulare)
Island tarplant (Deinandra clementina)
Island wallflower (Erysimum insulare)
Italian ryegrass (Festuca perennis)*
Italian thistle (Carduus pycnocephalus ssp. pycnocephalus)*
Ithuriel's spear (Triteleia laxa)
Ives' phacelia (Phacelia ivesiana)
Ivesia,
    Mousetail (Ivesia santolinoides)
    Rock (Ivesia saxosa)
    Silver-haired (Ivesia argyrocoma var. argyrocoma)
    Tahquitz (Ivesia callida)
Ivy, English (Hedera helix)*
Jeffrey pine (Pinus jeffreyi)
Jepsonia, Parry's (Jepsonia parryi)
Jepson's bedstraw (Galium jepsonii)
Jepson's morning glory (Calystegia malacophylla ssp. pedicellata)
Jerusalem-oak goosefoot (Dysphania botrys)*
Jewelflower,
    Cooper's (Caulanthus cooperi)
    Coulter's (Caulanthus coulteri)
    Heartleaf (Streptanthus cordatus var. cordatus)
    Laguna Mountains (Streptanthus bernardinus)
    Payson's (Caulanthus simulans)
    Slender-pod (Caulanthus heterophyllus)
    Southern (Streptanthus campestris)
Jimsonweed (Datura stramonium)*
Johnny jump up (Viola pedunculata)
Johnson's bee-hive cactus (Sclerocactus johnsonii)
Johnston's bedstraw (Galium johnstonii)
Johnston's buckwheat (Eriogonum microtheca var. johnstonii)
Johnston's bush lupine (Lupinus albifrons var. johnstonii)
Johnston's monkeyflower (Diplacus johnstonii)
Jointed buckwheat (Eriogonum intrafractum)
Jointed goatgrass (Aegilops cylindrica)*
Jojoba (Simmondsia chinensis)
Jones' blazing star (Mentzelia jonesii)
Jones' cloak fern (Argyrochosma jonesii)
Jones' cryptantha (Cryptantha muricata var. jonesii)
Jones' linanthus (Linanthus jonesii)
Joshua tree
    [Common] (Yucca brevifolia)
    Eastern (Yucca jaegeriana)
July gold (Dedeckera eurekensis)
Jumping cholla (Cylindropuntia bigelovii)
Junegrass (Koeleria macrantha)
Juniper,
    California (Juniperus californica)
    Grand (Juniperus grandis)
    Utah (Juniperus osteosperma)
Juniper mistletoe (Phoradendron juniperinum)
Jurupa Hills sun cup (Camissoniopsis ignota)
Kallstroemia, California (Kallstroemia californica)
Keckiella,
    Northern blue-stemmed (Keckiella ternata var. septentrionalis)
    San Jacinto Mountains (Keckiella rothrockii var. jacintensis)
Kelloggia (Kelloggia galioides)
Kellogg's knotweed (Polygonum polygaloides ssp. kelloggii)
Kellogg's tarplant (Deinandra kelloggii)
Kelso Creek monkeyflower (Erythranthe shevockii)
Kennedy's buckwheat (Eriogonum kennedyi var. kennedyi)
Kentucky bluegrass (Poa pratensis ssp. pratensis)*
Kern larkspur (Delphinium hansenii ssp. kernense)
Kern mallow (Eremalche parryi ssp. kernensis)
Kern sun cup (Camissonia kernensis ssp. gilmanii)
Kern tarplant (Deinandra pallida)
Keysia (Glyptopleura marginata)
Kidneyleaf buckwheat (Eriogonum reniforme)
Kikuyu grass (Pennisetum clandestinum)*
King's bladderpod (Physaria kingii ssp. kingii)
King's sandwort (Eremogone kingii var. glabrescens)
Knapp's brickellbush (Brickellia knappiana)
Knapweed,
    Russian (Acroptilon repens)*
    Spotted (Centaurea stoebe ssp. micranthos)*
Knobcone pine (Pinus attenuata)
Knot grass (Paspalum distichum)
Knot-stemmed bastard sage (Eriogonum wrightii var. nodosum)
Knotty buckwheat, see knot-stemmed bastard-sage
Knotweed,
    Common (Polygonum aviculare ssp. depressum)*
    Douglas's (Polygonum douglasii)
    Kellogg's (Polygonum polygaloides ssp. kelloggii)
    Sawatch (Polygonum sawatchense ssp. sawatchense)
    Swamp (Persicaria amphibia)
Krantz's catchfly (Silene krantzii)
Lace fern, California (Aspidotis californica)
Lace-fringed spineflower (Chorizanthe fimbriata var. laciniata)
Lace-pod (Thysanocarpus laciniatus)
Ladder brake (Pteris vittata)*
Ladies' fingers (Dudleya edulis)
Lady fern (Athyrium filix-femina var. cyclosorum)
Laguna Mountains aster (Dieteria asteroides var. lagunensis)
Laguna Mountains goldenbush (Ericameria cuneata var. macrocephala)
Laguna Mountains jewelflower (Streptanthus bernardinus)
Lakeside ceanothus (Ceanothus cyaneus)
Lamb's quarters (Chenopodium album)*
Lanceleaf browneyes (Chylismia claviformis ssp. lancifolia)
Lanceleaf dudleya (Dudleya lanceolata)
Langloisia, Bristly (Langloisia setosissima ssp. setosissima)
La purisima manzanita (Arctostaphylos purissima)
Large-flower baby blue eyes (Nemophila menziesii var. menziesii)
Large-flowered collomia (Collomia grandiflora)
Large-flowered cryptantha (Cryptantha intermedia var. intermedia)
Large-flowered leptosiphon (Leptosiphon grandiflorus)
Large-flowered lotus (Acmispon grandiflorus var. grandiflorus)
Large-flowered phacelia (Phacelia grandiflora)
Large-flowered pincushion (Chaenactis macrantha)
Large Heermann's buckwheat (Eriogonum heermannii var. heermannii)
Large-leaved avens (Geum macrophyllum var. perincisum)
Large-nosed monkeyflower (Erythranthe nasuta)
Large yellow primrose (Oenothera primiveris)
Larkspur,
    Blue (Delphinium parryi ssp. parryi)
    Colorado Desert (Delphinium parishii ssp. subglobosum)
    Desert (Delphinium parishii ssp. parishii)
    Gypsum-loving (Delphinium gypsophilum)
    Kern (Delphinium hansenii ssp. kernense)
    Mountain (Delphinium glaucum)
    Mountain spreading (Delphinium patens ssp. montanum)
    Pale (Delphinium parishii ssp. pallidum)
    Scarlet (Delphinium cardinale)
    Spreading (Delphinium patens ssp. hepaticoideum)
Late-flowering mariposa lily (Calochortus fimbriatus)
Latimer's woodland-gilia (Saltugilia latimeri)
Laurel sumac (Malosma laurina)
Lavender, Desert (Hyptis emoryi)
Lavender windows (Phacelia exilis)
Lax flower (Baileya pauciradiata)
Layia, Hawkweed (Layia hieracioides)
Layne's locoweed (Astragalus layneae)
Leafstem tickseed (Leptosyne calliopsidea)
Leafy buckwheat (Eriogonum fasciculatum var. foliolosum)
Leafy daisy (Erigeron foliosus var. foliosus)
Least duckweed (Lemna minuta)
Leather root,
    [Common] (Hoita macrostachya)
    Roundleaf (Hoita orbicularis)
Leather spineflower (Lastarriaea coriacea)
Lemmon's catchfly (Silene lemmonii)
Lemmon's linanthus (Leptosiphon lemmonii)
Lemmon's mustard (Caulanthus anceps)
Lemmon's phacelia (Phacelia lemmonii)
Lemmon's willow (Salix lemmonii)
Lemonade berry (Rhus integrifolia)
Lemon lily (Lilium parryi)
Leopard lily (Lilium pardalinum)
Leptosiphon, Large-flowered (Leptosiphon grandiflorus)
Lesser mohavea (Antirrhinum mohavea)
Lesser paintbrush (Castilleja minor ssp. spiralis)
Lesser wintergreen (Pyrola minor)
Lessingia,
    Spring (Lessingia tenuis)
    Sticky (Lessingia glandulifera var. glandulifera)
    Warner Springs (Lessingia glandulifera var. tomentosa)
Lewisia,
    Dwarf (Lewisia pygmaea)
    Sierra (Lewisia nevadensis)
Lewis's sun cup (Camissonia lewisii)
Licorice, Wild (Glycyrrhiza lepidota)
Lilac sunbonnets (Langloisia setosissima ssp. punctata)
Lily,
    Chocolate (Fritillaria biflora var. biflora)
    Corn (Veratrum californicum var. californicum)
    Desert (Hesperocallis undulata)
    Humboldt (Lilium humboldtii ssp. ocellatum)
    Lemon (Lilium parryi)
    Leopard (Lilium pardalinum)
    Pink funnel (Muilla coronata)
    Star (Zigadenus fremontii)
    Striped adobe (Fritillaria striata)
Limber pine (Pinus flexilis)
Limestone beardtongue (Penstemon calcareus)
Limestone monkeyflower (Erythranthe calcicola)
Limestone phacelia (Phacelia affinis)
Linanthus,
    Baldwin Lake (Linanthus killipii)
    Bigelow's (Linanthus bigelovii ssp. johnsonii)
    Common (Leptosiphon parviflorus)
    Desert (Linanthus demissus)
    Flax-flowered (Leptosiphon liniflorus)
    Jones' (Linanthus jonesii)
    Lemmon's (Leptosiphon lemmonii)
    Little San Bernardino Mountains (Linanthus maculatus ssp. maculatus)
    Many-flowered (Leptosiphon floribundus ssp. floribundus)
    Mojave (Leptosiphon breviculus)
    Parry's (Linanthus parryae)
    Pygmy (Leptosiphon pygmaeus ssp. continentalis)
    San Gabriel (Linanthus concinnus)
    Santa Rosa Mountains (Leptosiphon floribundus ssp. hallii)
    Smooth many-flowered (Leptosiphon floribundus ssp. glaber)
Lindley's blazing star (Mentzelia lindleyi)
Lip fern,
    Cleveland's (Myriopteris clevelandii)
    Cooper's (Myriopteris cooperae)
    Coville's (Myriopteris covillei)
    Parry's (Myriopteris parryi)
    Slender (Myriopteris gracilis)
    Viscid (Myriopteris viscida)
    Wooton's (Myriopteris wootonii)
Little desert trumpet (Eriogonum trichopes)
Little elephant heads (Pedicularis attollens)
Little gilia (Gilia minor)
Little gold poppy (Eschscholzia minutiflora)
Littleleaf palo verde (Parkinsonia microphylla)
Littleleaf redberry (Rhamnus crocea)
Littleleaf rhatany (Krameria erecta)
Little-leaved brickellbush (Brickellia microphylla var. microphylla)
Little-leaved mock orange (Philadelphus microphyllus)
Little-leaved Mojave indigo bush (Psorothamnus arborescens var. minutifolius)
Little-leaved mountain-mahogany (Cercocarpus ledifolius var. intricatus)
Little-leaved yellow penstemon (Keckiella antirrhinoides var. microphylla)
Little monardella (Monardella nana)
Little prince's pine (Chimaphila menziesii)
Little San Bernardino Mountains linanthus (Linanthus maculatus ssp. maculatus)
Little spring beauty (Claytonia exigua ssp. exigua)
Little wiry sun cup (Camissonia pusilla)
Live oak,
    Canyon (Quercus chrysolepis)
    Coast (Quercus agrifolia var. agrifolia)
    Interior (Quercus wislizeni var. wislizeni)
    Shrubby interior (Quercus wislizeni var. frutescens)
    Southern coast (Quercus agrifolia var. oxyadenia)
Lobed ground-cherry (Physalis lobata)
Lobelia,
    Dunn's (Lobelia dunnii var. serrata)
    Scarlet (Lobelia cardinalis var. pseudosplendens)
Locoweed,
    Coast (Astragalus trichopodus var. lonchus)
    Layne's (Astragalus layneae)
    Narrowpod (Astragalus filipes)
    Pomona (Astragalus pomonensis)
    Whitney's (Astragalus whitneyi var. whitneyi)
Locust,
    Black (Robinia pseudoacacia)*
    Desert (Robinia neomexicana)
Lodgepole pine (Pinus contorta ssp. murrayana)
Lomatium,
    California (Lomatium californicum)
    Caraway-Leaved (Lomatium caruifolium var. caruifolium)
    Fernleaf (Lomatium multifidum)
    Nevada (Lomatium nevadense var. nevadense)
    Parish's (Lomatium nevadense var. parishii)
    Shiny (Lomatium lucidum)
    Woolly (Lomatium dasycarpum ssp. dasycarpum)
London rocket (Sisymbrium irio)*
Long-anthered rush (Juncus macrandrus)
Long-beaked storksbill (Erodium botrys)*
Longbeak streptanthella (Streptanthella longirostris)
Long-flowered threadplant (Nemacladus longiflorus var. longiflorus)
Longfruit sun cup (Eremothera chamaenerioides)
Longleaf paintbrush (Castilleja subinclusa ssp. subinclusa)
Longleaf plantain (Plantago elongata)
Long-leaved aster (Symphyotrichum ascendens)
Long-leaved rush (Juncus macrophyllus)
Longspine horsebrush (Tetradymia axillaris var. longispina)
Long-spurred lupine (Lupinus arbustus)
Long-spurred plectritis (Plectritis ciliosa)
Longstalk phacelia (Phacelia longipes)
Longstem buckwheat (Eriogonum elongatum var. elongatum)
Loosestrife,
    California (Lythrum californicum)
    Hyssop (Lythrum hyssopifolia)
Lotebush (Ziziphus parryi var. parryi)
Lotus,
    Broad-leaved (Hosackia crassifolia var. crassifolia)
    California (Acmispon wrangelianus)
    Coastal (Acmispon maritimus var. maritimus)
    Davidson's (Acmispon nevadensis var. davidsonii)
    Heermann's (Acmispon heermannii var. heermannii)
    Hill (Acmispon brachycarpus)
    Large-flowered (Acmispon grandiflorus var. grandiflorus)
    Pygmy (Acmispon haydonii)
    Scrub (Acmispon argyraeus var. multicaulis)
    Short-bannered coastal (Acmispon maritimus var. brevivexillus)
    Sierra Nevada (Acmispon nevadensis var. nevadensis)
    Silver (Acmispon argophyllus var. argophyllus)
    Small-flowered (Acmispon micranthus)
    Streambank (Hosackia oblongifolia var. oblongifolia)
    Strigose (Acmispon strigosus)
Lousewort, Pine (Pedicularis semibarbata)
Love grass, Weeping (Eragrostis curvula)*
Low bush monkeyflower (Diplacus aridus)
Low canyon dudleya (Dudleya cymosa ssp. pumila)
Lowland cudweed (Gnaphalium palustre)
Lowland purslane (Trianthema portulacastrum)
Low phacelia (Phacelia humilis var. dudleyi)
Low pussytoes (Antennaria dimorpha)
Lupine,
    Anderson's (Lupinus andersonii)
    Arizona (Lupinus arizonicus)
    Arroyo (Lupinus succulentus)
    Bajada (Lupinus concinnus)
    Bentham (Lupinus benthamii)
    Brewer's (Lupinus breweri var. breweri)
    Broad-leaved (Lupinus latifolius var. latifolius)
    Bush (Lupinus longifolius)
    Chick (Lupinus microcarpus var. horizontalis)
    Coast bush (Lupinus arboreus)
    Clustered tidy (Lupinus lepidus var. confertus)
    Collar (Lupinus truncatus)
    Coulter's (Lupinus sparsiflorus)
    Desert (Lupinus shockleyi)
    Douglas's silver bush (Lupinus albifrons var. douglasii)
    Drew's silky (Lupinus adsurgens)
    Dune (Lupinus chamissonis)
    European yellow (Lupinus luteus)*
    Grape soda (Lupinus excubitus var. excubitus)
    Hall's bush (Lupinus albifrons var. hallii)
    Harlequin (Lupinus stiversii)
    Johnston's bush (Lupinus albifrons var. johnstonii)
    Long-spurred (Lupinus arbustus)
    Matted (Lupinus breweri var. bryoides)
    Meadow (Lupinus polyphyllus var. burkei)
    Miniature (Lupinus bicolor)
    Pale yellow (Lupinus luteolus)
    Peirson's (Lupinus peirsonii)
    Royal desert (Lupinus odoratus)
    San Jacinto (Lupinus hyacinthinus)
    Sand (Lupinus brevicaulis)
    Showy Brewer's (Lupinus breweri var. grandiflorus)
    Silky (Lupinus elatus)
    Silver bush (Lupinus albifrons var. albifrons)
    Silvery (Lupinus argenteus var. argenteus)
    Sky (Lupinus nanus)
    Southern mountain (Lupinus albifrons var. austromontanus)
    Stinging (Lupinus hirsutissimus)
    Summer (Lupinus formosus var. formosus)
    Valley (Lupinus microcarpus var. microcarpus)
    White-whorled (Lupinus microcarpus var. densiflorus)
    Yellow-eyed (Lupinus flavoculatus)
Lyon's pentachaeta (Pentachaeta lyonii)
Lyrepod, Coulter's (Lyrocarpa coulteri)