| K |
| Kadsura japonica, Kadsura |
| Kalimeris pinnatifida, False aster; Japanese aster |
| Kalmia angustifolia var. caroliniana, Sheep laurel; Wicky |
| Kalmia angustifolia var. caroliniana, Sheep laurel; Wicky |
| Kalmia latifolia, Mountain laurel |
| Kalmia latifolia, Mountain laurel |
| Kalopanax pictus, Castoraralia |
| Kerria japonica, Japanese kerria |
| Kniphofia, Red hot poker; Torch lily |
| Koeleria glauca, Large blue hair grass |
| Koelreuteria bipinnata, Chinese flame tree; Chinese goldenrain tree; Bougainvillea goldenrain tree |
| Koelreuteria paniculata, Goldenrain tree |
| Kolkwitzia amabilis, Beautybush |
| Kosteletzkya virginica, Seashore mallow; Coastal mallow |
| Krigia montana, Dwarf dandelion; Mountain krigia |