| Y |
| Yankee Lady rose, Rosa 'UHLater' |
| Yarrow, Achillea spp. |
| Yarrow, Common; Milfoil; Yarrow, Achillea millefolium |
| Yarrow, Wooly, Achillea tomentosa |
| Yellow angel's trumpet, Brugmansia x candida |
| Yellow Dazzler water lily, Nymphaea 'Yellow Dazzler' |
| Yellow floating heart; Yellow water fringe, Nymphoides pelatum |
| Yellow Fru Dagnor Hartopp rose, Rosa 'MORyerug' |
| Yellow loosestrife, Lysimachia punctata |
| Yellow-eyed grass, Xyris torta |
| Yellowrim, Serissa foetida |
| Yellowroot, Xanthorhiza simplicissima |
| Yellowwood, Cladrastis lutea |
| Yesterday rose, Rosa 'Yesterday' |
| Yew, Anglojap, Taxus x media |
| Yew, Chinese, Taxus chinensis |
| Yew, Duke Gardens, Cephalotaxus harringtonia 'Duke Gardens' |
| Yew, Golden, Taxus baccata 'Standishii' |
| Yew, Japanese plum, Cephalotaxus harringtonia |
| Yew, Japanese, Taxus cuspiduta |
| Yew, Prostrate Japanese plum, Cephalotaxus harringtonia 'Prostrata' |
| Yew, Repandens, Taxus baccata 'Repandens' |
| Yew, Upright, Taxus baccata 'Fastigiata Robusta' |
| Young Mistress rose, Rosa 'KORviga' |
| Yucca, Adam's needle, Yucca filamentosa |
| Yucca, Beaked; Big Bend yucca, Yucca rostrata |
| Yucca, Curveleaf; Pendulous yucca, Yucca recurvifolia |
| Yucca, Flaccid-leaf; Weakleaf yucca, Yucca flaccida |
| Yucca, Garland Gold, Yucca filamentosa 'Garland Gold' |
| Yucca, New Mexico, Yucca harrimaniae |
| Yucca, Pendulous; Curveleaf yucca, Yucca recurvifolia |
| Yucca, Spanish bayonet, Dagger plant, Yucca aloifolia |
| Yucca, Spanish dagger, Yucca gloriosa |
| Yucca, Weakleak; Flaccid leaf yucca, Yucca flaccida |
| Yucca; Spanish bayonet, Yucca filamentosa |
| Yue Yue Uen rose, Rosa 'Yue Yue Uen' |