The Story of Knock Out® Roses: William Radler's Disease-Resistant Revolution

William Radler, a Milwaukee native, turned a childhood fascination with roses into a breeding career that transformed the market. His Knock Out® series—starting with the original red shrub rose in 2000—combines black spot resistance, drought tolerance, continuous bloom, and self-cleaning habit. Over 3.5 million sold in a single year.

Breeding Philosophy

Radler’s 1.5-acre “Rosarium” tests hundreds of seedlings annually. He inoculates plants with disease pathogens, uses overhead watering to spread infection, and selects only those that stay clean and floriferous. Basement incubation allows year-round evaluation.

Key Introductions

• 2000: Knock Out® (red)
• 2001: Carefree Sunshine (yellow)
• 2002: Ramblin’ Red (climber)
• 2004: Blushing Knock Out®, Pink Knock Out®
• 2005: Double Knock Out®, Lemon Meringue (climber)
• 2006: Climbing Carefree Sunshine, Bright Eyes (climber, lemon-spicy scent)
• 2007: Rainbow Knock Out® (pink with yellow center)

Radler’s work proves that roses can be both beautiful and bulletproof—giving millions of gardeners the confidence to grow the “Queen of Flowers” without the royal headache.