Plants — H
- Haematoxylum campechianum Blackwood
- Hagenia abyssinica African Redwood
- Hamamelis Witch-hazel
- Hamamelis virginiana American Witchhazel
- Hamelia patens Firebush
- Handroanthus impetiginosus
- Handroanthus serratifolius Yellow Ipe
- Hannoa
- Harpagophytum Devil Claws
- Harrisonia perforata
- Harungana
- Hebanthe erianthos suma
- Hedera helix English Ivy
- Hedychium coronarium
- Hedychium spicatum Spiked Ginger Lily
- Hedysarum neglectum
- Heimia
- Heinsia crinita
- Helianthus annuus common sunflower
- Helianthus tuberosus Earth apple
- Helichrysum arenarium
- Helichrysum italicum
- Helichrysum petiolare
- Helicia cochinchinensis
- Helicia formosana Taiwan mountain longan
- Helicia nilagirica
- Helicia obovatifolia
- Helicteres baruensis
- Helicteres isora East Indian screwtree
- Heliotropium arboreum Tree Heliotrope
- Heliotropium europaeum European Turn-sole
- Helleborus Christmas-rose
- Helleborus foetidus Dungwort
- Helleborus odorus Sweet-scented Hellebore
- Helleborus purpurascens
- Helleborus viridis Green Hellebore
- Helwingia japonica
- Hemerocallis lilioasphodelus
- Hemidesmus indicus
- Hepatica hepaticas
- Hepatica nobilis Anemone hepatica
- Heracleum mantegazzianum
- Heracleum maximum American cow-parsnip
- Heracleum persicum Persian Hogweed
- Heracleum sibiricum Siberian cow-parsnip
- Heracleum sphondylium Cow Parsnip
- Heracleum villosum
- Heteranthera reniformis Kidneyleaf mud plantain
- Hibiscus Rose-mallow
- Hibiscus mutabilis Changeable Rose-mallow
- Hibiscus × rosa-sinensis China-rose
- Hibiscus sabdariffa Indian-sorrel
- Hibiscus syriacus Althea
- Hibiscus taiwanensis Taiwan cotton rose
- Hibiscus tiliaceus
- Hierochloë odorata Hierochloe odorata
- Hintonia octomera
- Hippocampus Seahorse
- Hippomane mancinella Manchineel
- Hippophae Sea buckthorns
- Hippophae rhamnoides sea buckthorn
- Hippophae salicifolia
- Hirudinea leech
- Histiopteris incisa
- Holarrhena densiflora
- Holarrhena floribunda
- Holarrhena mitis
- Holarrhena pubescens Bitter Oleander
- Homalanthus populneus Spurge
- Homalocladium platycladum Centipede plant
- Homonoia retusa
- Homonoia riparia Willow-Leaved Water Croton
- Hoodia gordonii Baboon Ghaap
- Hopea ferrea
- Horsfieldia irya
- Houpoea officinalis
- Houttuynia cordata Chameleon
- Humulus Hop
- Humulus lupulus Bine
- Huperzia Club-moss
- Huperzia selago Fir Club Moss
- Huperzia serrata Toothed Clubmoss
- Hura crepitans Dynamite Tree
- Hyacinthus orientalis Common Hyacinth
- Hydnocarpus chaulmoogra trees
- Hydnora africana Cape jackalskos
- Hydrangea
- Hydrangea aspera rough-leaf hydrangea
- Hydrangea macrophylla
- Hydrastis canadensis Goldenseal
- Hydrocera triflora Marsh Henna
- Hydrocharis morsus-ranae Common Frogbit
- Hydrocotyle umbellata Manyflower Marshpennywort
- Hylomecon vernalis Forest poppy
- Hylotelephium telephium Live-forever
- Hymenaea courbaril Brazilian Cherry
- Hymenocallis Spiderlily
- Hyoscyamus niger Black Henbane
- Hypericum
- Hypericum attenuatum
- Hypericum elongatum
- Hypericum hircinum Stinking Tutsan
- Hypericum hirsutum
- Hypericum maculatum Imperforate St John's-wort
- Hypericum montanum
- Hypericum perforatum St. John's wort
- Hypericum scabrum
- Hypericum triquetrifolium Curled-leaved St. John's-wort
- Hyptis crenata
- Hyptis suaveolens
- Hyssopus officinalis Hyssop