Index of plants by genus
| Species | Common Name | Family |
| Halesia tetraptera | Carolina Silverbell | Styracaceae |
| Hamamelis virginiana | American Witchhazel | Hamamelidaceae |
| Helenium autumnale | Sneezeweed | Asteraceae |
| Helianthemum canadense | Longbranch Frostweed | Cistaceae |
| Helianthus angustifolius | Narrow-leaved Sunflower | Asteraceae |
| Helianthus decapetalus | Thin-leaved Sunflower | Asteraceae |
| Helianthus divaricatus | Woodland Sunflower | Asteraceae |
| Helianthus grosseserratus | Sawtooth Sunflower | Asteraceae |
| Helianthus microcephalus | Small-headed Sunflower | Asteraceae |
| Helianthus mollis | Downy Sunflower | Asteraceae |
| Helianthus occidentalis | Western Sunflower | Asteraceae |
| Helianthus tuberosus | Jerusalem Artichoke | Asteraceae |
| Heliopsis helianthoides | False Sunflower | Asteraceae |
| Hepatica acutiloba | Sharp-lobed Hepatica | Ranunculaceae |
| Hepatica americana | Round-lobed Hepatica | Ranunculaceae |
| Heracleum maximum | Cow Parsnip | Apiaceae |
| Heuchera americana | Common Alumroot | Saxifragaceae |
| Heuchera richardsonii | Prairie Alumroot | Saxifragaceae |
| Hieracium paniculatum | Panicled Hawkweed | Asteraceae |
| Hieracium scabrum | Rough Hawkweed | Asteraceae |
| Hieracium venosum | Rattlesnake Weed | Asteraceae |
| Houstonia caerulea | Little Bluet | Rubiaceae |
| Houstonia longifolia | Long-leaved Bluet | Rubiaceae |
| Houstonia purpurea | Large Bluet | Rubiaceae |
| Hudsonia ericoides | Pine-barren False Heather | Cistaceae |
| Hudsonia tomentosa | Sand False Heather | Cistaceae |
| Huperzia appressa | Mountain Firmoss | Lycopodiaceae |
| Huperzia lucidula | Shining Firmoss | Lycopodiaceae |
| Hydrangea arborescens | Wild Hydrangea | Saxifragaceae |
| Hydrangia quercifolia | Oakleaf Hydrangea | Saxifragaceae |
| Hydrophyllum canadense | Canada Waterleaf | Hydrophyllaceae |
| Hydrophyllum virginianum | Virginia Waterleaf | Hydrophyllaceae |
| Hylocomium splendens | Stairstep Moss | Hylocomiaceae |
| Hypericum ascyron ssp. pyramidatum | Great St. John's Wort | Hypericaceae |
| Hypericum canadense | Canadian St. John's Wort | Hypericaceae |
| Hypericum densiflorum | Bushy St. John's Wort | Hypericaceae |
| Hypericum denticulatum | Coppery St. John's Wort | Hypericaceae |
| Hypericum ellipticum | Pale St. John's Wort | Hypericaceae |
| Hypericum gentianoides | Orange-grass | Hypericaceae |
| Hypericum kalmianum | Kalm's St. John's Wort | Hypericaceae |
| Hypericum majus | Greater Canada St. John's Wort | Hypericaceae |
| Hypericum mutilum | Dwarf St. John's Wort | Hypericaceae |
| Hypericum prolificum | Shrubby St. John's Wort | Hypericaceae |
| Hypericum punctatum | Spotted St. John's Wort | Hypericaceae |
| Hypericum stragulum | Low St. John's Wort | Hypericaceae |
| Hypopitys monotropa | Yellow Pine-sap | Ericaceae |
| Hypopitys lanuginosa | Hairy Pine-sap | Ericaceae |
| Hypoxis hirsuta | Yellow Star Grass | Amaryllidaceae |
| Hystrix patula | Bottlebrush Grass | Poaceae |
© 2004-2009 Michael Hough