Helosciadium inundatum
Lesser Marshwort
Helosciadium nodiflorum
Fool's-water-cress
Heracleum mantegazzianum
Giant Hogweed
Heracleum sphondylium
Hogweed
Hesperis matronalis
Dame's-violet
Hieracium repandulare
Hippophae rhamnoides
Sea-buckthorn
Hippuris vulgaris
Mare's-tail
Hirschfeldia incana
Hoary Mustard
Honckenya peploides
Sea Sandwort
Hornungia petraea
Hutchinsia
Humulus lupulus
Hop
Hydrocotyle vulgaris
Marsh Pennywort
Hypericum androsaemum
Tutsan
Hypericum hircinum
Stinking Tutsan
Hypericum humifusum
Trailing St John's-wort
Hypopitys monotropa
Yellow Bird's-nest
Iberis amara
Wild Candytuft
Iberis umbellata
Garden Candytuft
Ilex aquifolium
Holly
Impatiens glandulifera
Indian Balsam
Iris foetidissima
Stinking Iris
Isatis tinctoria
Woad
Isolepis setacea
Bristle Club-rush