| Cultivar | Plant Size | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Terry Wogan' | Medium | Blue/Green | - | - | Sport | Pale-Lavender | August | Ford, Richard & Ford, Mary | .2006 |
| 'Thelma M. Pierson' | Large | Yellow | - | - | Sport | Light-Purple | June into July | Pierson, Robert | .1988 |
| 'Thelma Rudolph' | Large | Med-Green | - | - | Unknown | - | - | Ward, Dr Dick & Ward, Jane | --NR-- |
| 'Theodore Roosevelt' | Large | Light-Green | - | - | Unknown | Pale-Lavender | June into July | Sugita, Hajime & Ruh, Peter | .2001 |
| 'Thomas Hogg' | Medium | Med-Green | Marginal | White | Unknown | - | - | Bailey, Liberty Hyde & The American Hosta Society | --NR-- |
| 'Thomas Jefferson' | Large | Yellow | - | - | Unknown | Near-White | June into July | Sugita, Hajime & Ruh, Peter | .2001 |
| 'Timothy C. Morgan' | Medium | Blue/Green | Medial | White | Unknown | Pale-Lavender | July into August | Chamberlain, Steve | .2005 |
| 'Timothy J. Wright' | Medium | Yellow | - | - | Unknown | Med-Lavender | - | Chamberlain, Steve | .2015 |
| 'Tom Gannon' | Medium | Med-Green | Streaked | Yellow | Hybrid | Near-White | June into July | Zolock, Steve & Zolock, Sarah | .2005 |
| 'Tom Rex' | - | - | - | - | Duplicate | - | - | Duplicate Name | --NR-- |
| 'Tom Schmid' | Giant | Blue/Green | Marginal | Creamy White | Sport | Pale-Lavender | July into August | Schmid, Tom | .1995 |
| 'Tom Terrific' | Large | Yellow | - | - | Hybrid | Pale-Lavender | July into August | Solberg, Robert | .2019 |
| 'Tom Thumb' | Miniature | Med-Green | - | - | Unknown | - | - | Fransen, Marco | --NR-- |
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