| English Name | Scientific Name | Spanish Name |
| Jacaranda Tree | — Jacaranda mimosifolia J. coerulea |
— Jacaranda Abey, Gualanday |
| Jacobs Ladder | Polemonium grandiflorum | Alahocaptli leptofilo |
| Jaltomato | Jaltomata procumbens | Cachumba, Dulce, Jaltomata(e), Pacheca, Pucheca, Seresa, Tomate arenoso, Tomatillo negro |
| Jamaica Fever Plant, Puncture Vine | —
Tribulus spp |
—
Abrojo, A. rojo |
| Jamaican Dogwood | Piscidia erythrina | Arbol del coral, Piscidia |
| Japanese Plum | Eriobotrya japonica | Nispero |
| Japanese Seaweed | Undaria pinnatifida | Alga wakame, Naruto wakame |
| Jasmin | Jasminum officinalis | Jasmin |
| Java Tea | Orthosiphon aristatus | Te de riñon |
| Jerusalem Sage | Phlomis purpurea | Matagallo |
| Jerusalem Thorn, Horsebean | Parkinsonia aculeata | Palo vérde, Retama |
| Joe Pye Weed, Boneset, Ague Weed, Gravel Root, Trumpet Weed, Queen of the Meadow, Hemp Agrimony (1) | —
Eupatorium areolare |
—
Borreguilla |
| Joe Pye Weed, … (2) | — E. odoratum E. perfoliatum E. purpureum E. petiolare E. quadrangulare |
— Crucetillo oloroso, Tayoco Hierba del angel, Eupatorio Reina de los prados, Ulmaria Amargocilla, Hierba amargosa, Hierba (Yerba) del ángel, H. del burro, H. del perro, Huirapen, Peistó grande, Pestó, Pexto, Sopa, Yolochichitl Hierba del jabalí |
| Jointvetch | Aeschynomene villosa var. villosa | Amor seco |
| Jojoba | Simmondsia chinensis | Cohobe, Jojoba |
| Jujube, Chinese Date | Zizyphus jujuba | Azufaifo |
| Juliana, Cuachalalà Tree | Juliania adstringens or Amphipterygium adstringens | Cuachalate, Cuachalala, Cuachalalate, Cuachalalote |
| Juniper, Cedar (1) — Eastern Red Cedar Common Juniper Alligator Juniper, Checker-barked Cedar |
— Juniperus lycia J. virginiana J. communis J. deppeana var. deppeana |
— Copal, Incienso de iglesia Cedro Bayas de enebro, Bellota de sabina(o), Cedra, Enebro, Guata, Junípero, Nebrina Enebro, Oyorique, Táscate Táscate, Wahaka |
| Juniper, Cedar (2) Drooping Juniper Utah Juniper Prickly Juniper Alligator Juniper Broadmoor savin Juniper |
— J. flaccida J. osteosperma J. oxycedrus J. pachyphlaea J. sabina |
— Junipero llorón, Sabino, S. montés Junípero Cada Táscate Sabina |
| Kelp, Bladderwrack, Brown Algae, Seaweed | —
Fucus versiculosus Laminaria spp |
—
Alga marina, A. fucus, Encina de mar, Fuco verigoso, Fucus vesicoso, Sargazo vejigoso |
| Kidney Vetch | Anthyllis vulneraria | Vulneraria |
| Kidneywood | Daldinia concentrica | Arbol de Palo dulce, A. de azul, Cuate, Coatillo, Cualadulce, Palo azul, P. dulce, P. cuate, Rosilla, Taray, Vara dulce, Varaduz |
| King Alfreds Cakes, Crampbells | Daldinia concentrica | Bola de madera |
| Kola Nut | Cola acuminata | Nuez kola |
| Kudzu | Pueraria lobata | Kudzu |
