| Cultivar Name | Plant Size | Leaf Color | Variegation | Var Color | Origin | Flower Color | Season | Source | Registered |
| 'Ralph's Legacy' | Small | Med-Green | Streaked | Speckles | Unknown | - | July into August | Zolock, Steve & Zolock, Sarah | .2000 |
| 'Rashao Iwa' | Miniature | Dark-Green | - | - | Unknown | - | - | Suzuki, Kichigoro | --NR-- |
| 'Raspatini' | Miniature | Med-Green | - | - | Hybrid | Light-Purple | August | Zilis, Mark | .2009 |
| 'Raspberry Sundae' | Small | Dark-Green | Medial | White | Unknown | Pale-Lavender | August to October | Korlipara, Harini & Gossett, Gary & Terra Nova Nurseries | --NR-- |
| 'Ready' | Large | Dark-Green | - | - | Unknown | Med-Lavender | - | Livingston, Ron | --NR-- |
| 'Ready Eddy' | Small | Blue/Green | - | - | Unknown | - | - | Benedict, Dr Ralph (Herb) | --NR-- |
| 'Red Alert' | Small | Med-Green | Medial | White | Hybrid | Light-Purple | July into August | Unknown | --NR-- |
| 'Red Bar' | Medium | Med-Green | Marginal | White | Unknown | | | Malloy, Alex | --NR-- |
| 'Red Bull' | Large | Med-Green | - | - | Hybrid | - | July into August | Van Eechaute, Danny | .2010 |
| 'Red Cadet' | Medium | Dark-Green | - | - | Hybrid | Pale-Lavender | August to October | Van Eechaute, Danny | .2005 |
| 'Red Cloud' | Small | Blue/Green | Streaked | White | Hybrid | - | - | Beilstein, Doug | --NR-- |
| 'Red Corvette' | Medium | Med-Green | - | - | Hybrid | Light-Purple | August to September | Moore, Jeff & Schwarz, Jim | .2015 |
| 'Red Dog' | Medium | Med-Green | - | - | Unknown | - | - | Terpening, Kent | --NR-- |
| 'Red Dragon' | Medium | Light-Green | - | - | Hybrid | Light-Purple | August | Livingston, Ron | --NR-- |
| 'Red Eagle' | - | - | - | - | Hybrid | - | - | Moore, Jeff | --NR-- |
| 'Red Feather' | Medium | Dark-Green | - | - | Unknown | - | - | Benedict, Dr Ralph (Herb) | --NR-- |
| 'Red Grande' | Medium | Dark-Green | - | - | Unknown | - | - | Benedict, Dr Ralph (Herb) | --NR-- |
| 'Red Grange' | Medium | Blue/Green | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Red Hots' | - | Yellow | - | - | Hybrid | - | - | Goodenough, Rick | --NR-- |
| 'Red Imp' | Medium | Med-Green | - | - | Hybrid | Light-Purple | - | Lydell, Ransom | --NR-- |
| 'Red Kitty' | Small | Med-Green | - | - | Unknown | - | - | Terpening, Kent | --NR-- |
| 'Red Legged Plover' | Medium | Yellow | - | - | Hybrid | - | - | Moore, Jeff | --NR-- |
| 'Red Legs' | Large | Dark-Green | - | - | Hybrid | - | August to October | Sugita, Hajime & Ruh, Peter | .1998 |
| 'Red Light' | Medium | Dark-Green | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Red Neck Heaven' | Medium | Med-Green | - | - | Hybrid | Pure-White | July into August | Avent, Tony | .1998 |
| 'Red October' | Medium | Dark-Green | - | - | Hybrid | Light-Purple | September to October | Herold, Roy & Walek, Kevin | .2009 |
| 'Red One' | Small | Dark-Green | - | - | Unknown | - | - | Westberg, Jim | --NR-- |
| 'Red Puppy' | Medium | Med-Green | - | - | Unknown | - | - | Livingston, Ron | --NR-- |
| 'Red Racer' | Medium | Med-Green | | | Hybrid | | | Vissers, Louis | --NR-- |
| 'Red Rampage' | - | Med-Green | Streaked | White | Unknown | - | - | Lydell, Ransom | --NR-- |
| 'Red Reject' | Medium | Med-Green | - | - | Unknown | - | - | Stegeman, Bev & Stegeman, Dave | --NR-- |
| 'Red Riding Hood' | Medium | Med-Green | - | - | Unknown | - | - | Malloy, Alex | --NR-- |
| 'Red River' | Small | Dark-Green | - | - | Hybrid | - | - | Malloy, Alex | --NR-- |
| 'Red Rover' | Medium | Med-Green | - | - | Hybrid | Med-Lavender | August to September | Moore, Jeff & Schwarz, Jim | .2015 |
| 'Red Sox' | Medium | Dark-Green | - | - | Hybrid | Light-Purple | August to October | Herold, Roy & Walek, Kevin | .2009 |
| 'Red Spatz' | Medium | Dark-Green | - | - | Unknown | - | - | Summers, Alex | --NR-- |
| 'Red Stem Green' | Medium | Med-Green | - | - | Unknown | Deep-Purple | August | Wade, Van | --NR-- |
| 'Red Stilts' | Large | Med-Green | - | - | Hybrid | Pale-Lavender | June into July | Van Eechaute, Danny | .2011 |
| 'Red Thunder' | Medium | Med-Green | - | - | Hybrid | - | - | Beilstein, Doug & Malloy, Alex | --NR-- |
| 'Red Titanium' | | Blue/Green | | | Hybrid | | | Leuckx, Bart | --NR-- |
| 'Red Wedding' | - | - | - | - | Unknown | - | - | Vasey, Mike | --NR-- |
| 'Red Wine Fries' | Medium | Blue/Green | - | - | Hybrid | Med-Lavender | - | Van Wyke, Trudy | --NR-- |
| 'Redback Tavern' | Medium | Med-Green | Medial | Yellow | Hybrid | - | - | Wrede, Arthur | --NR-- |
| 'Reddish Dot' | Medium | Med-Green | - | - | Hybrid | Deep-Purple | July into August | Liu, Donghuan | .2016 |
| 'Reddy Eddy' | Large | Dark-Green | - | - | Unknown | - | August to September | Benedict, Dr Ralph (Herb) & Kuenster, Rod | .2010 |
| 'Redneck Mardi Gras' | Small | Yellow | - | - | Unknown | Deep-Purple | August to September | Duncan, Mary Jo | .2016 |
| 'Redon Bleu' | Large | Blue/Green | - | - | Unknown | - | - | Livingston, Ron | --NR-- |
| 'Remembrance' | Medium | Blue/Green | Marginal | Yellow | Hybrid | - | June into July | Skaggs, Virginia & Skaggs, Brian & Gilligan, Madelon | .2015 |
| 'Respighi' | Medium | Med-Green | - | - | Unknown | - | - | Unknown | --NR-- |
| 'Rhubarb Girl' | Large | Blue/Green | | | Unknown | | | Carlson, Monty & Carlson, Julie | --NR-- |
| 'Rhubarb Pie' | Medium | Med-Green | - | - | Sport | Pale-Lavender | August | Johnson, Irwin | .2001 |
| 'Rikyu' | Medium | Med-Green | Medial | Yellow | Unknown | - | - | Fukatsu, Shinya | --NR-- |
| 'Rock Happy' | Medium | Med-Green | - | - | Hybrid | Med-Lavender | August | Ruh, Peter | .1992 |
| 'Rocket's Red Glare' | Medium | Med-Green | - | - | Hybrid | - | - | Stegeman, Bev & Stegeman, Dave | --NR-- |
| 'Rosedale Light My Fire' | Small | Yellow | - | - | Unknown | - | - | Hadrava, Jerry | --NR-- |
| 'Rough Lemon' | Medium | Yellow | | | Unknown | | | Solberg, Robert | --NR-- |
| 'Round About Midnight' | Medium | Blue/Green | | - | Hybrid | Pale-Lavender | July into August | Dean, Don | .2019 |
| 'Royal Persuasion' | Small | Dark-Green | - | - | Unknown | - | - | King, Jim | --NR-- |
| 'Royal Purple' | Large | Med-Green | - | - | Hybrid | - | - | Wrede, Arthur | --NR-- |
| 'Royal Regal Rhubarb' | Large | Med-Green | Marginal | White | Sport | Light-Purple | July into August | Benedict, Dr Ralph (Herb) | --NR-- |
| 'Royal Rhubarb' | Large | Med-Green | - | - | Hybrid | Light-Purple | July into August | Ruh, Peter & Ruh, Jean | .2005 |
| 'Rubies and Ruffles' | Medium | Dark-Green | Marginal | White | Unknown | Med-Lavender | August to September | Goodwin, Randy | .2009 |
| 'Ruby' | Small | Med-Green | - | - | Hybrid | Light-Purple | August to September | Savory, Dennis | .2013 |
| 'Ruby Slippers' | Medium | Med-Green | - | - | Hybrid | Light-Purple | September | Ward, Dr Dick & Ward, Jane | .1999 |
| 'Ruby Tuesday' | Small | Med-Green | - | - | Unknown | - | - | Herold, Roy | --NR-- |
| 'Ruffed Up' | Large | Yellow | - | - | Hybrid | Pale-Lavender | August to September | Carlson, Monty & Carlson, Julie | .2009 |
| 'Ruffles and Flourishes' | Small | Light-Green | Marginal | White | Unknown | Near-White | July | Goodwin, Randy | .2019 |
| 'Run Around' | Medium | Med-Green | - | - | Unknown | - | July into August | Benedict, Dr Ralph (Herb) & Kuenster, Rod | .2010 |
| 'Rust Bucket' | Medium | Yellow | - | - | Unknown | - | - | Goodenough, Rick | --NR-- |
| 'Rusty Bee' | Medium | Med-Green | - | - | Hybrid | Light-Purple | July | Malloy, Alex | .1998 |
|