| Hostaname | RG | SZ | Leaf color | P | F | Origin |
| H. 'Ugly Duckling' Zilis/Ruh 1999 | R | ML | ygr,we | | | 'Gold Regal' sport |
| H. 'Ulee's Gold' B. Treichel 2006 | R | | goy | | | unknown |
| H. 'Ultramarine' Mark Zilis/M. Vanous 2003 | R | M | bl | | | 'Sea Lotus Leaf' x kikutii f. leuconota |
| H. 'Ultraviolet Light' Jim & Jill Wilkins 1989 | R | ML | y>ch | | | 'Gold Regal' hybrid |
| H. 'Ulysses S. Grant' H. Sugita/M. Zilis/P. & J. Ruh 2001 | R | VL | blgr | | | unknown |
| H. 'Unbridled Passion' G. Johnson 2004 | R | | | | | ('Neat Splash' x 'Northern Halo') x 'Maekawa' |
| H. 'Unchained Melody' J. Wilkins/S. Wilkins 2000 | R | | gr,gye | | | 'DB-87-2' x 'Elatior' |
| H. 'Uncle John' Frank Nyikos 2000 | R | | blgr | | | 'Blue Splendor' x 'Halcyon' |
| H. 'Unducosa' Alex J. Summers/AHS 1986 | R | M | gr | | | 'Undulata' x ventricosa |
| H. 'Undulata' Bailey 1930/W. G. Schmid/AHS 2001 | R | ML | w,gre | | | Japan:Nagasaki |
| H. 'Undulata Albomarginata' Maekawa 1936/AHS 1987 | R | M | gr,we | | | 'Undulata' sport |
| H. 'Undulata Erromena' Maekawa 1936/AHS 1987 | R | M | gr | | | 'Undulata' sport |
| H. 'Undulata Univittata' Hylander 1954/AHS 1987 | R | M | w,gre | | | 'Undulata' sport |
| H. 'Unexpected Company' G. Herold 2005 | R | M | gry,dgre | | | 'Great Expectations' hybrid |
| H. 'Unexpected Pleasure' Stuart Asch 2000 | R | | gr,cre | | | 'Dorothy Benedict' x montana |
| H. 'Unexpected Song' J. Wilkins/S. Wilkins 2000 | R | | dgr | | | 'Leading Lady' sport |
| H. 'Unforgettable' R. Kuk 1999 | R | LM | dgr,ye | | | ('Gold Regal' x "gold Tokudama seedling") sport |
| H. 'Unique' Eunice V. Fisher/Peter Ruh 1991 | R | L | gr | | | |
| H. 'Upbeat' P. Ruh 2000 | R | L | gr | | | (x fluctuans) hybrid |
| H. 'Upper Crust' Mark Zilis 2004 | R | | (lg>cr),dgre | | | 'Snow Crust' sport |
| H. 'Uptown Girl' Hans Hansen 2007 | R | | gr | | | 'Iwa Hansen' x 'Ming Treasure' |