On Growing Roses: Cultivars for Use in Colorado’s Post-Japanese Beetle Life

By Susan Wroble, May 2020

What’s a rose lover to do? Japanese Beetles invaded the Denver area in 2006 and have exploded in numbers ever since. While some home gardeners are ripping out their rose beds, Colorado State University’s Dr. Whitney Cranshaw had a much better plan. Dr. Cranshaw, a Professor of Entomology, undertook a two-year study to determine the cultivars to use in our post-Japanese Beetle landscape.

With more than 200 cultivars, the War Memorial Rose Garden in Littleton provided Dr. Cranshaw and his team a unique opportunity to study both Japanese Beetle Damage and visitation by pollinating bees. Damage by the beetles was evaluated on a sliding three-point scale. There was wide variation in the levels of beetle damage, but the rose classes which sustained the least damage were Hybrid Teas, Landscape Shrubs, and Grandifloras. The greatest incidence of Japanese Beetle damage occurred on Shrub roses.

About eleven percent of the cultivars had both high Japanese Beetle damage and high visitation by pollinators, including honey bees, bumble bees and solitary bees. Planting for pollinators is typically desirable, but Dr. Cranshaw notes that this group of roses, which is highly visited by both the beetles and bees, presents the most challenges for management as the need for controls are the greatest but the pesticide options are limited. These roses are the least sustainable, and Dr. Cranshaw recommends against further plantings.

Cultivars with Both High Japanese Beetle Damage and High Bee Visitation

Not Recommended for Planting (Due to Restricted Insecticide Options)

Miniature Floribunda Grandiflora
Prima Donna Easy Does It Glowing Peace
Rainbow Knock Out Eureka
First Edition
Morden Sunrise
Hybrid Tea Climber Shrub
Elle Climbing New Dawn Carefree Spirit
Honey Perfume Fourth of July Carefree Delight
Hot Coco Day Dream
Lady Elsie May
Moon Dance
Pescali
Touch of Class
Starry Night

Roses to Plant! The great news of the study was that eighteen cultivars had little to no damage by Japanese Beetles and are thus recommended as being sustainable in the landscape.

Recommended for Planting: Cultivars with Little to No Damage from Japanese Beetles

NAME TYPE (As defined in Study) COLOR FRAGRANCE
Angel Face Floribunda Mauve purple blend Strong
Carrot Top Miniature Orange blend Mild
Child’s Play Miniature White with pink edge None to mild
Class Act Floribunda White None to mild
Colossus Hybrid tea Deep Yellow Strong
Cupcake Miniature Pink Mild
Electron Hybrid Tea Cherry Pink Mild to strong
French Lace Floribunda White, Pink undertones Mild
Gemini Hybrid Tea Pink blend Mild
Jean Kenneally Miniature Apricot blend Mild
Joseph’s Coat Climber Red blend Moderate
Merlot Hybrid Tea Red, white reverse Mild
Old Glory Hybrid Tea Pink Strong
Perfecta Miniature (?) ? ?
Picotee Hybrid Tea (?) Red/white blend Mild
Rainbow Sorbet Shrub Deep pink, yellow edge None to mild
Shining Hour Hybrid Tea Deep Yellow Moderate
Sun Sprinkles Hybrid Tea (?) Deep Yellow Mild

If endless summers of hand-picking Japanese Beetles off your roses seems daunting, there is now hope. Instead, you can spend your summers enjoying Cupcakes and Rainbow Sorbet, with Merlot by your side. Thanks, Dr. Cranshaw!

Notes:

Perfecta is listed in Help Me Find as a Miniature and a Hybrid Tea. However, there are no known photos of the Miniature version, but the Hybrid Tea version is popular.

Picotee is listed in Help Me Find as a Miniature and Floribunda

Sun Sprinkles is listed in Help Me Find as a Miniature

2 thoughts on “On Growing Roses: Cultivars for Use in Colorado’s Post-Japanese Beetle Life”

  1. Love it! Last summer I found masses of Japanese beetles in a nearby park, and several around our yard. I hope I don’t have to rip out my roses (NOOOOOOOO!), but if I do, now I’ve got a clue what to replace them with.
    Thanks, Susan!

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