Index of plants by genus
| Species | Common Name | Family |
| Lactuca canadensis | Tall Lettuce | Asteraceae |
| Laportea canadensis | Canadian Woodnettle | Urticaceae |
| Larix laricina | Tamarack | Pinaceae |
| Ledum groenlandicum | Labrador Tea | Ericaceae |
| Lathyrus palustris | Marsh Vetchling | Fabaceae |
| Leersia oryzoides | Rice Cutgrass | Poaceae |
| Leersia virginica | White Grass | Poaceae |
| Leiophyllum buxifolium | Sand-myrtle | Ericaceae |
| Lemna minor | Common Duckweed | Lemnaceae |
| Leucobryum glaucum | White Pincushion Moss | Leocobryaceae |
| Leucothoe racemosa | Sweetbells | Ericaceae |
| Liatris aspera | Rough Blazing Star | Asteraceae |
| Liatris cylindricacea | Cylindrical Blazing Star | Asteraceae |
| Liatris pilosa | Shaggy Blazing Star | Asteraceae |
| Liatris pycnostachya | Prairie Blazing Star | Asteraceae |
| Liatris scariosa | Northern Blazing Star | Asteraceae |
| Liatris squarrosa | Scaly Blazing Star | Asteraceae |
| Liatris spicata | Marsh Blazing Star | Asteraceae |
| Lilium canadense | Canada Lily | Liliaceae |
| Lilium michiganense | Michigan Lily | Liliaceae |
| Lilium philadelphicum | Wood Lily | Liliaceae |
| Lilium superbum | Turk's Cap Lily | Liliaceae |
| Lindera benzoin | Spicebush | Lauraceae |
| Lindernia dubia | False Pimpernel | Scrophulariaceae |
| Linnaea borealis | Twinflower | Caprifoliaceae |
| Linum medium var. texanum | Small Yellow Flax | Linaceae |
| Liparis liliifolia | Lily-leaved Twayblade | Orchidaceae |
| Liparis loeselii | Green Twayblade | Orchidaceae |
| Liquidambar styraciflua | Sweetgum | Hamamelidaceae |
| Liriodendron tulipifera | Tuliptree | Magnoliaceae |
| Lithospermum canescens | Hoary Puccoon | Boraginaceae |
| Lithospermum incisum | Fringed Puccoon | Boraginaceae |
| Lithospermum latifolium | American Gromwell | Boraginaceae |
| Lobelia canbyi | Canby's Lobelia | Campanulaceae |
| Lobelia cardinalis | Cardinal Flower | Campanulaceae |
| Lobelia dortmanna | Water Lobelia | Campanulaceae |
| Lobelia inflata | Indian Tobacco | Campanulaceae |
| Lobelia kalmii | Kalm's Lobelia | Campanulaceae |
| Lobelia nuttallii | Nuttall's Lobelia | Campanulaceae |
| Lobelia siphilitica | Blue Lobelia | Campanulaceae |
| Lobelia spicata | Spiked Lobelia | Campanulaceae |
| Lonicera canadensis | American Fly Honeysuckle | Caprifoliaceae |
| Lonicera dioica | Red Honeysuckle | Caprifoliaceae |
| Lonicera hirsuta | Hairy Honeysuckle | Caprifoliaceae |
| Lonicera oblongifolia | Swamp Fly Honeysuckle | Caprifoliaceae |
| Lonicera prolifera | Yellow Honeysuckle | Caprifoliaceae |
| Lonicera sempervirens | Scarlet Honeysuckle | Caprifoliaceae |
| Lonicera villosa | Mountain Fly Honeysuckle | Caprifoliaceae |
| Luzula acuminata | Hairy Wood Rush | Juncaceae |
| Lycopodiella alopecuroides | Foxtail Bog Clubmoss | Lycopodiaceae |
| Lycopodiella appressa | Southern Bog Clubmoss | Lycopodiaceae |
| Lycopodiella inundata | Northern Bog Clubmoss | Lycopodiaceae |
| Lycopodium clavatum | Staghorn Clubmoss | Lycopodiaceae |
| Lycopodium lagopus | One-cone Clubmoss | Lycopodiaceae |
| Lygodium palmatum | American Climbing Fern | Lygodiaceae |
| Lupinus perennis | Wild Lupine | Leguminosae |
| Lycopus americanus | Common Waterhorehound | Lamiaceae |
| Lycopus uniflorus | Northern Bugleweed | Lamiaceae |
| Lysimachia ciliata | Fringed Loosestrife | Primulaceae |
| Lysimachia lanceolata | Lance-leaved Loosestrife | Primulaceae |
| Lysimachia quadriflora | Narrow-leaved Loosestrife | Primulaceae |
| Lysimachia quadrifolia | Whorled Loosestrife | Primulaceae |
| Lysimachia terrestris | Swamp Candles Loosestrife | Primulaceae |
| Lysimachia thyrsiflora | Swamp Loosestrife | Primulaceae |
| Lythrum alatum | Winged Loosestrife | Lythraceae |
© 2004 Michael Hough