Hallucinogens 1 (up to 1950's) - 10 items, including The Boston Daily Globe 1956 "Columbian Jungle Area Untouched by Civilization".
Hallucinogens 2 (1960's) - 42 items, including The Coral Gables Times 1968 "Hallucination Drug Cult Faces Legal Test".
Hallucinogens 3 - 17 items, including The New York Times 1978 "Doctor Links Indian Art to Drugs".
Hallucinogens 4 - 14 items, including The Seattle Times 1985 "Botanist says he's unmasked mystery", Newsweek 1982 "Guns, Grass and Monday".
Halophytes - 2 items.
Hamamelis - 3 items.
Hats - 14 items, including Field Museum News 1939 "Straw Hats", Gardeners' Chronicle 1915 "The Bamboo Hat Industry".
Hay Fever - 25 items, including New York Times 1982 "Mushroom Spores Suspected as Culprit in Allergic Reactions that Baffled Specialists", Newsweek 1982 "Allergies: New Discoveries, New Relief".
Helianthus - 28 items, including The New York Times 1983 "An Artichoke to Grow in the Sun", The Garden 918 "A Sunflower Village".
Heliotropium - 1 item.
Helleborus - 2 items.
Hemerocallis - 1 item.
Hemlock - 4 items, including The Garden Magazine 1910 "Is the Southern Hemlock Better".
Hemp - 8 items, including Commerce Reports 1931 "Hemp Experiments in Columbia".
Hepatica - 3 items.
Herbals - 6 items, including The New York Times 1981 "Medieval Manuscripts".
Herbaria - 2 items.
Herbicides - 7 items, including The New York Times 1982 "Panel sees problem in study of effects of agent orange",
Herbs 1 - 32 items, including The Garden 1925 "Some Culinary Herbs Worth Cultivating", The Gardeners' Chronicle 1929 "Curious Old Beliefs About Medicinal Herbs".
Herbs 2 - 45 items, including Life 1961 "A New Urge for Herbs", Field Museum News 1941 "Medicinal Science was Father of Botanical Studies".
Herbs 3 - 61 items, including The Real Paper 1981 "Consumer Beware: Unhealthful Herbs", New York Times 1977 "Herbs to Grow for Refreshing Cups of Tea", The American Weekly 1959 "The Search for Life-giving Herbs".
Herb-Clip - 8 items.
Hernandia - 1 item.
Hevea - 16 items, including Arnolidia 1984 "The Tree that Changed the World in One Century" by Richard Evans Schultes.
Hibiscus - 17 items, including The Agricultural News 1904 "Musk Seed".
Hickory - 5 items, including The New York Times 1936 "Hardest Wood Used for Skis".
Hieracium - 1 item.
Hippophae - 2 items.
Hoheria - 1 item.
Holcus - 2 items.
Honey - 24 items, including The New York Times 1983 "Radioactivity Found in Bees".
Hops - 10 items.
Horticulture - 53 items, including The Boston Globe 1981 "Plants can be an educational hobby", The New York Times 1936 "Patents for Plants".
Hura - 1 item.
Hydrastis - 1 item.
Hydrilla - 1 item.
Hydroponics - 3 items.
Hypericum - 1 item.
Hyptis - 1 item.