Winter damage to roses and boxwood

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

As spring continues to advance, more woody plants are showing damage from this past winter. Several county offices have received an increasing number of inquiries about damage to roses and boxwood. While it’s not uncommon to see extensive dieback on hybrid tea roses, this year we’re also seeing damage to shrub roses, including hardy Canadian and Buck roses. Boxwood damage varies from a few branches to the whole plant. Even the newer, hardier hybrids out of Canada and Morton Arboretum (e.g. Green Velvet, Green Mountain, Glencoe) are damaged.

Why are these cold hardy plants affected?

While these plants tolerate our Zone 5 cold temperatures, it’s the swing in winter temperatures that caused the damage this past winter. When plants are subjected to long periods of warm weather in the winter, they are fooled into thinking it’s time to wake up and start growing. They start to lose their cold temperature tolerance. Then, when the cold temperatures return, these plants cannot withstand the cold temperatures they could before the warming period. Bottom line: plant tissue is damaged

What can you do?

Many of these plants are pushing out new growth and should survive. Prune out the dead and damaged wood to maintain plant health and vigor. For pruning tips, refer to Tom Fernandez’s article in the April 13, 2007, Landscape Alert.

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