| | | | |
| H | Genus | Species | Cultivar | Common Name |
 | HEBE | | 'Mrs. Winder' | AGM |
| HEBE | | 'Nicola's Blush' | AGM |
| HEBE | | 'Pink Tip' | |
| HEBE | | 'Purple Queen' | |
| HEBE | | 'Spender's Seedling' | |
| HEBE | albicans | | AGM |
| HEBE | cupressoides | 'Boughton Dome' | |
| HEBE | hulkeana | | |
| HEBE | pinguifolia | 'Pagei' | AGM |
| HEBE | recurva | | |
| HELENIUM | | 'Dunkelpracht' (dark beauty) | |
| HELENIUM | | 'Flammenspiel' | |
| HELENIUM | | 'Moerheim Beauty' | AGM |
| HELENIUM | | 'Sahin's Early Flowerer' | AGM |
| HELENIUM | | 'Waltraut' | AGM |
| HELENIUM | | 'Zimbelstern' | |
| HELIANTHEMUM | | 'Lawrenson's Pink' | |
| HELIANTHEMUM | | 'Wisley Pink' | |
| HELIANTHEMUM | | 'Wisley Primrose' | |
| HELIANTHUS | | 'Lemon Queen' | AGM |
| HELIANTHUS | salicifolius | | |
| HELICHRYSUM | petiolare | | AGM |
| HELICHRYSUM | petiolare | 'Gold' | |
| HELICHRYSUM | petiolare | 'Variegatum' | AGM |
| HELIOTROPIUM | arborescens | | Cherry Pie syn. H.peruvianum |
| HELLEBORUS | argutifolius | | AGM syn. H. corsicus |
| HELLEBORUS | foetidus | | AGM |
| HELLEBORUS | niger | | AGM Christmas Rose |
| HELLEBORUS | thibetanus | | |
| HELLEBORUS | viridis | | |
| HELLEBORUS | x hybridus | Bradfield Hybrids | Fully Double |
| HELLEBORUS | x hybridus | Bradfield Hybrids | Anemone Centered |
| HELLEBORUS | x hybridus | Bradfield Hybrids | |
| HELLEBORUS | x nigercors | | AGM |
| HELLEBORUS | x sternii | | |
| HEMEROCALLIS | | 'American Revolution' | |
| HEMEROCALLIS | | 'Catherine Woodbery' | |
| HEMEROCALLIS | | 'Christmas Island' | |
| HEMEROCALLIS | | 'Cosmopolitan' | |
| HEMEROCALLIS | | 'Cream Drop' | |
| HEMEROCALLIS | | 'Golden Chimes' | AGM |
| HEMEROCALLIS | | 'Mountain Laurel' | |
| HEMEROCALLIS | | 'Stafford' | |
| HEMEROCALLIS | | 'Summer Wine' | |
| HEMEROCALLIS | citrina | | |
| HEMEROCALLIS | fulva | 'Flore pleno' | Day Lily |
| HEMEROCALLIS | lilioasphodelus | | AGM |
| HEPATICA | transsilvanica | | AGM |
| HEPATICA | transsilvanica | 'Blue Jewel' | AGM |
| HEPATICA | transsilvanica | 'Elison Spence' | |
| HEPATICA | x media | 'Ballardii' | |
| HESPERIS | matronalis | 'Alba Plena' | |
| HESPERIS | matronalis | var albiflora | |
| HEUCHERA | | 'Can-Can' | |
| HEUCHERA | | 'Chocolate Ruffles' | |
| HEUCHERA | | 'Obsidian' | |
| HEUCHERA | | 'Palace Purple Select' | syn. H.diversifolia 'P.P' |
| HEUCHERA | | 'Plum Pudding' | |
| HEUCHERA | sanguinea | 'Ruby Bells' | |
| HOSTA | | 'Aphrodite' | |
| HOSTA | | 'Honeybells' | AGM |
| HOSTA | crispula | | AGM |
| HOSTA | fortunei | | |
| HOSTA | fortunei | 'Francee' | AGM |
| HOSTA | sieboldiana | | |
| HOSTA | sieboldiana var. elegans | | AGM |
| HOSTA | undulata | var. undulata | AGM syn. H.mediovariegata |
| HUMULUS | lupulus | 'Aureus' | Golden Hop |
| HYACINTHOIDES | non-scriptus | | Bluebell |
| HYDRANGEA | anomala | subsp.petiolaris | AGM Climbing Hydrangea syn. H.petiolaris |
| HYDRANGEA | arborescens | 'Annabelle' | AGM |
| HYDRANGEA | aspera | subsp.sargentiana | AGM |
| HYPERICUM | androsaenum | 'Albury Purple' | |