Hackberry (Celtis spp.)
Hackberry budgall psyllid (Pachypsylla celtidisgemma)
Hackberry, Common/Western (Celtis occidentalis)
Hackberry, Spiny/Granjeno (Celtis pallida)
Hairgrass (Aira spp.)
Hairgrass, crinkled (Deschampsia flexcrosa)
Hairgrass, Little (Aira praecox)
Hairgrass, Silver (Aira caryophyllea)
Halo Blight (Pseudomonas syringae)
Haloe Koa (Leucaena leucocephala)
Halogeton (Halogeton glomeratus)
Haole, Kao (Leucaena glauca)
Hard lock (Fusarium spp.)
Hardhack (Spiraea tomentosa)
Hardlock (Fusarium verticillioides)
Hasardia (Haplopappus squarrosus)
Hau (Hibiscadelphus bombycinus)
Haw (Crataegus pinnatifida)
Hawaiian flower thrips (Thrips hawaiiensis)
Hawksbeard (Crepis spp.)
Hawksbeard, Asiatic (Youngia japonica)