| Cultivar Name | Plant Size | Leaf Color | Variegation | Var Color | Origin | Season | Source | Registered |
| 'Katherine S. Mahoney' | Medium | Med-Green | - | - | Unknown | September to October | Chamberlain, Steve | .2006 |
| 'Katsuragawa Beni' | Medium | Med-Green | - | - | Unknown | August to October | Masoka, Hiroshi | --NR-- |
| 'Kelsey' | Medium | Med-Green | - | - | Hybrid | August to October | Williams, Frances & Ruh, Peter | .1996 |
| 'Kifukurin Mizu' | Small | Dark-Green | Marginal | Yellow | Nat-Sport | September to October | Unknown | --NR-- |
| 'Kikeika' | Small | Dark-Green | - | - | Nat-Sport | September to October | Unknown | --NR-- |
| 'Kikeika Mizu' | Small | Med-Green | - | | Nat-Sport | September to October | Unknown | --NR-- |
| 'Kinakafu' H. longissima | Small | Dark-Green | Medial | Yellow | Nat-Sport | September to October | Honda | --NR-- |
| 'King of Spades' | Medium | Dark-Green | - | - | Hybrid | August to October | Beilstein, Doug & Mardy | .2007 |
| 'Kingfisher' | Medium | Blue/Green | - | - | Unknown | August to October | Smith, Eric & BHHS | .1988 |
| 'Kiss an Angel Good Morning' | Medium | Dark-Green | Marginal | Yellow | Hybrid | October | Kwick, Charles | .2018 |
| 'Kiss to Remember' | Small | Yellow-Gold | - | - | Hybrid | September to October | Kwick, Charles | .2018 |
| 'Kokuryu' | Medium | Med-Green | - | - | Unknown | October | Nakayama, Toyozo, Kurasawa, Tsuneo & Ruh, Peter | .2000 |
| 'Komyo Nishiki' | Small | Med-Green | Medial | White | Nat-Sport | August to October | Unknown | --NR-- |
| 'Kyoto' | Medium | Med-Green | - | - | Hybrid | August to October | Sugita, Hajime & Ruh, Peter | .2001 |
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