Extension News

Dr. Grow-It-All Prepares Roses and Strawberries for Winter

Note to media editors: This is the ISU Extension Garden Column for the week of Nov. 2, 2007.

10/29/2007

By James Romer
Horticulturist
Iowa State University Extension

Unfortunately, it’s time to put away the suntan lotion and plastic pink flamingos.  Winter is just around the corner.  Here are some tips to put roses and strawberries to bed for the winter.

Bush-type roses such as hybrid teas, floribundas and grandifloras need to be protected during our harsh winters (hardy shrub roses should make it through the winter months with minimal care). Prepare bush-type roses for winter when plants are dormant after exposure to two or three hard frosts. Normally, that is in late October to early November in northern Iowa, mid-November in central areas, and mid- to late November in southern counties.

To begin, remove fallen leaves and other debris from around each plant. This will help reduce disease problems next season. Then loosely tie the canes together with twine to prevent the canes from being whipped by strong winds. Extremely tall canes can be cut back to 2-1/2 to 3 feet. Next, mound soil 10 to 12 inches high around the base of the canes. Place additional material, such as straw or leaves, over the mound of soil after the ground freezes. A small amount of soil placed over the straw or leaves should hold these materials in place.

Many home gardeners protect their roses by placing styrofoam rose cones over them. Unfortunately, rose cones by themselves do not provide adequate protection. Additional material is necessary. If using styrofoam rose cones, prune the canes back to allow the cone to fit over the plant.

Remove any plant debris, then mound 6 to 8 inches of soil around the base of the canes. Set the cone over the plant. Finally, mound a small amount of soil around the outside base of the cone to keep it in place. Secure the cone by placing a brick or other heavy object on its top. Remove protective materials before bud break in spring, normally late March in southern Iowa and mid-April in northern Iowa.

Cold winter temperatures and repeated freezing and thawing of the soil through the winter months are the main threats to strawberry plants. Temperatures below 20 degrees F may kill flower buds and damage the roots and crowns of unmulched plants. Plants also can be destroyed by repeated freezing and thawing of the soil, which can heave unmulched plants out of the ground.

Strawberries should be mulched in fall before temperatures drop below 20 degrees F. However, allow the strawberry plants to harden or acclimate to cool fall temperatures before mulching the planting. Plants that are mulched prematurely are more susceptible to winter injury than those that are mulched after they have been properly hardened. In northern Iowa, strawberries are normally mulched in late October to early November. Gardeners in central and southern Iowa should mulch their strawberry plantings in mid-November and mid- to late November, respectively.

Excellent mulching materials include clean, weed-free oat, wheat or soybean straw or even chopped cornstalks. Apply 3 to 5 inches of mulch at application. This should eventually settle to 2 to 4 inches. In windy, exposed areas, straw mulches can be kept in place by placing wire or plastic fencing over the area. The fencing can be held in place with bricks or other heavy objects.

Leaves are not suitable winter mulch for strawberries. Leaves can mat together in layers, trapping air and creating space for ice to form. The leaf, air and ice layers do not provide adequate protection. Leaf mulch may actually damage plants due to excess moisture trapped under the material.

Taking a few moments this fall to protect roses and strawberries will end up with you having plenty of strawberry shortcake and smelling like a rose next year!

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Contacts :

James Romer, Horticulture, (515) 294-2336, jromer@iastate.edu

Jean McGuire, Extension Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu