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Hippophae rhamnoides
Hippophae rhamnoides, sea buckthorn (Elaeagnaceae), a hardy nitrogen-fixing Eurasian shrub with seven subspecies, orange vitamin-rich berries used in food and traditional medicine, and limited clinical evidence of benefit.
Histiopteris incisa
Histiopteris incisa (Thunb.) J.Sm., the bat's wing fern or water fern (mātā), is a widespread Dennstaedtiaceae fern of the tropics and subtropics, with 1–2 m pale green fronds, marginal continuous sori, and Least Concern to Critically Endangered regional statuses.
History of cannabis
History of cannabis (Cannabis sativa): Eurasian domestication for fiber, food, and medicine; earliest psychoactive use at Jirzankal Cemetery; O'Shaughnessy's 19th-century medical promotion; 1925 Geneva control, 1937 US Marijuana Tax Act, and modern legalization.
History of maize
The history of maize traces its single domestication from wild teosinte in Mexico's Balsas River valley about 9,000 years ago, its spread through the Americas, and its global rise after 1492.
History of the potato
History of the potato (Solanum tuberosum): Andean domestication ~10,000 years ago, sixteenth-century Spanish introduction to Europe, Chilean subspecies adoption, the Great Irish Famine, demographic effects, and modern genome-based breeding.
History of wheat
Wheat, first domesticated in the Fertile Crescent around 10,000 years ago, gave rise to bread wheat by hybridization 8,500 to 9,000 years ago and became the world's most widely grown crop.
Höganäs Formation
Höganäs Formation (Höganäsformationen), Rhaetian–Hettangian (Upper Triassic–Lower Jurassic) mudstone, sandstone and coal unit in Skåne, southern Sweden; Vallåkra, Bjuv, Helsingborg members; coal mined until 1961; rich Rhaetian floras.
Hoh Rainforest
Hoh Rainforest, in Olympic National Park, Washington, is an old-growth temperate rainforest on the Hoh River receiving about 140 inches of rain yearly, known for the Hall of Mosses trail, moss-draped giants, and its 2025 road-washout closure.
Holcus
Holcus (velvetgrass) is a small genus of annual and perennial Poaceae grasses, tribe Poeae, subtribe Holcinae, native from Macaronesia and Europe to the Caucasus and South Africa; type species Holcus lanatus, Yorkshire fog, a forage grass and weed.
Holcus lanatus
Holcus lanatus, Yorkshire fog or velvet grass, is a tufted perennial grass native to Europe, Macaronesia, and the Caucasus, naturalized worldwide, a prolific seeder, pasture forage, lawn weed, and invasive in California coastal prairies.
Holcus mollis
Holcus mollis (creeping soft grass) is a rhizomatous perennial Poaceae grass native to Europe and NW Africa, with chromosome races 2n=28, 35, 42, 49, exserted awns, and bearded nodes, distinct from Holcus lanatus.
Holly
Holly (Ilex, Aquifoliaceae): the sole genus of its family, over 664 dioecious tree and shrub species. Originated in subtropical Asia in the early Eocene; famous species include Ilex aquifolium, the Christmas holly.
Holodiscus discolor
Holodiscus discolor, oceanspray or creambush (Rosaceae), a deciduous arching shrub native from British Columbia to Mexico, with creamy white flower sprays, four varieties, fire-adapted, valuable to native bees.
Honey locust
Honey locust (Gleditsia triacanthos), also called sweet-locust or thorny-locust, is a thorned North American legume tree with sweet pods, thornless urban cultivars, and invasive populations in Argentina, Europe, and Australia.
Honeycrisp
Honeycrisp (MN 1711) is a crisp, juicy apple cultivar released by the University of Minnesota in 1991; DNA later confirmed parentage Keepsake × MN1627. It became a top US variety, Minnesota State Fruit in 2006, and parent of Cosmic Crisp, SweeTango, and others.
Honeydew (melon)
Honeydew melon (Cucumis melo var. inodorus), a smooth-rinded winter melon with sweet green flesh; stored at 7-10°C, harvested at 10° Brix minimum, also called the Wallace melon in China.
Honeynut squash
Honeynut squash, a personal-sized butternut-type winter squash (Cucurbita moschata hybrid), bred at Cornell by Robinson, Jahn, and Mazourek with chef Dan Barber; released 2015, sweeter with 2-3x the beta-carotene of butternut and edible thin skin.
Honeysuckle
Honeysuckle, genus Lonicera (Caprifoliaceae), about 160 Northern Hemisphere species of fragrant vines and shrubs; Japanese honeysuckle (Lonicera japonica) is a major invasive vine in North America, while Lonicera sempervirens is a native alternative.
Hopea
Hopea is a genus of about 100 dipterocarp timber trees from Sri Lanka to New Guinea, known as merawan timber, distinguished from Shorea by two long fruit calyx wings and nested phylogenetically within Shorea.
Hops
Hops, the female cones of Humulus lupulus (Cannabaceae), are the brewing crop that bitters, flavors, and preserves beer via alpha acids and essential oils; cultivated since the 8th-century Hallertau, with over 260 varieties and medicinal uses.
Hordeum
Hordeum (barleys), a genus of Triticeae grasses in Poaceae, includes cultivated barley Hordeum vulgare, the fourth most grown cereal, domesticated about 10,000 years ago from H. spontaneum; recognized by triplet spikelets and x=7 chromosomes.
Hordeum murinum
Hordeum murinum, wall barley or false barley, a weedy annual grass with three subspecies (glaucum, leporinum, murinum) native from Europe to the Himalaya, now a herbicide-resistant crop and pasture weed harming sheep worldwide.
Hornbeam
Hornbeam (Carpinus), a birch-family hardwood genus of about 19-40 Northern hemisphere species; European hornbeam (C. betulus) is a 25 m coppice and hedging tree of heavy lowland soils, with very hard wood used for cogs and mallets.
Hornwort
Hornworts (Anthocerotophyta) are a bryophyte division of about 220 species with a horn-shaped, continuously growing sporophyte, single chloroplasts with pyrenoids, and Nostoc cyanobacterial symbiosis, sister to liverworts plus mosses.
Hornworts of Great Britain
The hornworts of Great Britain are the four species of the plant division Anthocerotophyta recorded in the country, most often on bare, damp arable clay and loam.
Hornworts of Ireland
The hornworts of Ireland are the hornwort plants recorded from Ireland: three confirmed taxa, Anthoceros agrestis, Anthoceros punctatus, and Phaeoceros laevis, with Phaeoceros carolinianus unresolved.
Horseradish
Horseradish (Armoracia rusticana), a Brassicaceae perennial from southeastern Europe and western Asia, grown over 3,000 years for its pungent taproot; allyl isothiocyanate from sinigrin gives the heat, and it substitutes for wasabi.
Hosta
Hosta, or plantain lily, is a genus of shade-loving foliage perennials in Asparagaceae native to East Asia, introduced to the West by von Siebold in 1829-1830, with thousands of registered cultivars and slugs and Hosta Virus X as chief problems.
Hottest chili pepper
Hottest chili pepper: Pepper X, bred by Ed Currie of PuckerButt Pepper Company, holds the Guinness record since October 2023 at 2,693,000 SHU average, dethroning the Carolina Reaper (1.64 million SHU).
Houseplant
Houseplant: an indoor container plant, mostly tropical species grown for decoration and wellbeing. Key species include snake plant, pothos, peace lily, and ZZ plant; NASA air-cleaning claims do not scale to real rooms.