Weed Herbarium – by Scientific Name
| Hackelia virginiana | beggarslice | Boraginaceae - Borage Family |
| Helianthus tuberosus | Jerusalem artichoke | Asteraceae (Compositae) - Aster or Sunflower Family |
| Heracleum maximum | see - Heracleum lanatum | |
| Heracleum lanatum | cow parsnip | Apiaceae (Umbelliferae) - Carrot Family |
| Hesperis matronalis | damesrocket | Brassicaceae (Cruciferae) - Mustard Family |
| Hibicus tronium | Venice mallow | Malvaceae - Mallow Family |
| Hieracium caespitosum | see - Hieracium pratense | |
| Hieracium lachenalii | see - Hieracium vulgatum | |
| Hieracium aurantiacum | orange hawkweed | Asteraceae (Compositae) - Aster or Sunflower Family |
| Hieracium paniculatum | panicled hawkweed | Asteraceae (Compositae) - Aster or Sunflower Family |
| Hieracium pratense | hawkweed | Asteraceae (Compositae) - Aster or Sunflower Family |
| Hieracium vulgatum | European hawkweed | Asteraceae (Compositae) - Aster or Sunflower Family |
| Holcus lanatus | common velvet grass | Poaceae (Graminae) - Grass Family |
| Houstonia caerulea | bluets | Rubiaceae - Madder Family |
| Humulus japonicus | Japanese hops | Cannabaceae - Hemp Family |
| Hypericum perforatum | St. Johnswort | Hyperiacaceae - St. Johnswort Family |
| Hypochaeris radicata | cat's ear | Asteraceae (Compositae) - Aster or Sunflower Family |