|  Hieracium venosum (Rattlesnake-Weed)
 |  Hordeum jubatum (Squirrel-Tail Grass)
 |  Houstonia caerulea (Common Bluets)
 |  Houstonia longifolia (Long-Leaved Houstonia)
 |  Houstonia serpyllifolia (Creeping Bluets)
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|  Hybanthus concolor (Green Violet)
 |  Hydrangea arborescens (Wild Hydrangea)
 |  Hydrastis canadensis (Goldenseal)
 |  Hydrocotyle americana (American Water-Pennywort)
 |  Hydrocotyle umbellata (Umbellate Water-Pennywort)
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|  Hydrophyllum appendiculatum (Appendaged Waterleaf)
 |  Hydrophyllum canadense (Broad-Leaved Waterleaf)
 |  Hydrophyllum virginianum (Virginia Waterleaf) - Dark Purple Flowers
 |  Hydrophyllum virginianum (Virginia Waterleaf) - Light Purple Flowers
 |  Hydrophyllum virginianum (Virginia Waterleaf) - White Flowers
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|  Hypericum ascyron (Great St. Johnswort)
 |  Hypericum canadense (Lesser Canadian St. Johnswort)
 |  Hypericum densiflorum (Bushy St. Johnswort)
 |  Hypericum ellipticum (Pale St. Johnswort)
 |  Hypericum hypericoides (St. Andrew's Cross)
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|  Hypericum mutilum (Dwarf St. Johnswort)
 |  Hypericum prolificum (Shrubby St. Johnswort)
 |  Hypericum punctatum (Spotted St. Johnswort)
 |  Hypopitys monotropa (Pinesap)
 |  Hypoxis hirsuta (Yellow Stargrass)
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|  Ilex montana (Mountain Winterberry)
 |  Ilex mucronata (Catberry)
 |  Ilex verticillata (Common Winterberry)
 |  Impatiens capensis (Spotted Jewelweed)
 |  Impatiens pallida (Pale Jewelweed)
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|  Impatiens pallida (Pale Jewelweed) - Pale Flower
 |  Iodanthus pinnatifidus (Purple Rocket)
 |  Ionactis linariifolia (Stiff Aster)
 |  Ipomoea pandurata (Wild Potato Vine)
 |  Iris cristata (Dwarf Crested Iris)
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|  Iris lacustris (Dwarf Lake Iris)
 |  Iris versicolor (Large Blue Flag) - Side View
 |  Iris versicolor (Large Blue Flag) - Top View
 |  Iris virginica (Virginia Iris)
 |  Isotria verticillata (Large Whorled Pogonia)
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|  Jeffersonia diphylla (Twinleaf)
 |  Juglans cinerea (Butternut) - Female Flowers
 |  Juglans cinerea (Butternut) - Male Flowers
 |  Juncus acuminatus (Sharp-Fruited Rush)
 |  Juncus balticus (Baltic Rush)
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|  Juncus brachycephalus (Small-Headed Rush)
 |  Juncus effusus (Soft Rush)
 |  Juncus tenuis (Path Rush)
 |  Juncus torreyi (Torrey's Rush)
 |  Justicia americana (American Water-Willow)
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