Last roses of summer

Horticulture Hints

With the arrival of autumn, area rose gardeners are enjoying a new flush of fall blooms. After a long, hot summer, most roses will produce a new batch of flowers in response to the less stressful environment provided by cooler days of the season. Interestingly, Irish poet Thomas Moore was inspired by this burst of fall bloom from an old garden rose when he wrote “The Last Rose of Summer” in 1805.

Many roses will continue to bloom until the first hard frost. During the fall, roses start preparations for winter. Triggered by shorter day length and lower temperatures, rose plant cells transfer water to outside the cell wall, leaving a flexible, thin film of water within the cell. This allows the plant cells to freeze without being ruptured by ice crystals.

Roses that can survive our cold Iowa winters have been derived from species rose mutations and adaptations. These tough hardy roses were then hybridized to create new plants that are able to adjust and endure the difficult winter conditions experienced locally.

Roses vary in their degree of cold hardiness. Most shrub roses will not need winter protection. To help other types of roses survive the winter, apply about 12 inches of compost mulch or soil around base of plant after the ground freezes. Water bushes well before soil is frozen completely will help to lessen winterkill damage. Download the ISU publication “Care of Modern Roses in Iowa” at: https://store.extension.iastate.edu/Product/RG310.pdf for further information on overwintering roses.

Did you know? Most folks are familiar with Knock Out® roses which are commonly grown for their hardiness and disease resistance. Some earlier rose introductions, also hardy to our northern Iowa area, include the group of Canadian Explorer Roses. Named after early surveyors, these roses include John Cabot, Henry Kelsey and William Baffin. These three roses produce long shoots can be used on a trellis, similar to a climbing rose, as true climbers are not reliably winter hardy in our area.

Questions? Contact McCormick at yvonne@iastate.edu for information or advice.

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