Are Knockout Roses Hardy in Zone 5?

Knock Out roses are as hardy as old shrub roses.

The growing family of Knock Out roses includes red, pink, yellow and bicolor single and double blooms on sturdy shrubs. The original Knock Out had several ancestor roses hardy to zones 4 and 5.

Radler's Roses

Knock Out roses are an expanding hybrid group created by William Radler, former director of Boerner Botanical Gardens in Milwaukee, Wisconsin and consultant for the Chicago Botanic Garden's Krasberg Rose Garden. Milwaukee and Chicago are both within zone 5.

Considerations

Radler's "Rosarium," where he perfected the Knock Out series, beginning with the original red Knock Out in 1988, is in Greenfield, Wisconsin, a suburb of Milwaukee. His primary goals were to develop plants that were cold-hardy and black spot-resistant. To date, seven Knock Out hybrids have accomplished both objectives.

Significance

Knock Out roses may also grow in traditional zone 4b areas. Hardiness zones have shifted north in many areas, according to the Arbor Day Foundation's interpretation of National Oceanic and Atmospheric Administration data. Conard-Pyle, the company that markets Knock Outs, claims hardiness to zone 5 for them.

References

• Chicago Botanic Garden: Krasberg Rose Garden
• Conard-Pyle Company: William Rader, Rose Breeder
• National Gardening Association: Sustainable Roses?
• Arbor Day Organization: Hardiness Zones

Resources

• Conard-Pyle Company: How to Care for Knock Out Roses
• Triple Oaks Nursery and Herb Garden: Another Knock Out Rose in the Ring