Successfully growing roses in Wisconsin

During a meeting sponsored by the Dodge County Master Gardeners, Sherry Shaft and Joan Schultz from the Madison Rose Society described the difference between what is officially termed a shrub rose and those that fit into other classifications.

They also shared ideas for successfully growing roses in the Wisconsin climate, preventing disease and dealing with insects.

Shaft is a Master Gardener, a Consulting Rosarian, and rose arrangement judge. She is a frequent volunteer at Olbrich Botanical Gardens in Madison and a contributing author in the 2009 and 2010 Wisconsin Garden Journal.

Schultz is a Consulting Rosarian and a Rose Horticulture judge. Both presenters have spoken at Wisconsin Garden Expo in Madison.



Different types of roses

Shaft explained the different types of roses, beginning with the shrub rose. She said, "The only problem with them is they get so many flowers that it takes a lot of time to deadhead them."

The Knockout series is another hardy shrub variety developed at Boerner Botanical Gardens. They are ramblers or climbers.

The Carefree series of shrub rose is very easy to take care of and will bloom even when it isn't deadheaded. Within that series, the Polar Joy more closely resembles a tree that blooms constantly. She has one among her other shrub roses and says the only problem is it gets many suckers.

The Hybrid tea roses need more care than the shrub type. They are not as winter hardy so some of them will need special protection in winter and others are simply not suited to this climate.

Other types include the Grandiflora or Floribundi, rose bushes that are somewhat hardier than the Hybrid Tea.

Climbing roses come in a variety of colors and traits. They typically get seven to eight feet tall but some have been known to climb even higher.

Miniatures and Miniflora roses are also climbing and come in different varieties and colors including the Green Ice that starts the season white, then has mint green flowers and ends the season with pink.



Caring for roses

When it comes to care for roses, Shaft says the shrub roses need no special care and will survive just fine on their own over winter. Others will need some protection to survive.

She says, "Don't cut your roses in fall. Wait until spring and then cut the dead part off the top."

Shaft says the only way she will cut a rose in fall is if it is too tall for wrapping with burlap or slipping under a cone cover but she stresses, "If you trim the plant in spring it will be more vigorous and hardy and get more blooms. If it is very windy, however, the plant needs to be trimmed or it may break off from the wind."

She admits it isn't so much the cold that hurts roses in winter but the wind and the thawing and freezing, changing temperatures.

On her hybrid tea varieties she places a collar around them in fall and fills it with dirt, then waits for it to freeze before covering with a cone. The cone needs breathing holes and leaves need to be removed from the plant before covering.

She also places mouse pellets on the dirt before placing the cone on the plant. In spring remove the cone and the dirt.

Shaft has also had success leaving the plant in a pot. Bury the plant in the garden in summer and then dig it out and move the potted plant into a garage or cold storage room over winter. If it freezes it's okay as long as it isn't thawing and freezing or extremely low temperatures. It will need some water before storing but not as much as when it is growing in summer.

The floribundas and miniatures get a cover of bark or leaves in the fall. Spread out the mulch in spring or place it back into a pot and set aside for use again in fall. When using leaves, choose oak or harder variety that will not rot before spring.



Combatting diseases

As for diseases, Blackspot is the most typical on all but the Knockout roses. Plants must be treated with a fungicide before the Blackspot is visible and fungicides should be alternated so the disease does not become immune to a particular type.

A non-chemical alternative is to mix one cup of milk with two cups of water and spray it on the plants once a week. That method was developed by Jeff Gillman of the University of Minnesota and has been successful.

"Always remove the bottom leaves of your plants in spring," Schultz recommends. "Blackspot comes from water splashing off the soil onto the leaves."

Downy mildew is similar but is more of a purple color and tends to follow the veins. Shaft says it is important to identify the problem before treating. Mildew can be treated simply by spraying with water.

"Better air circulation around your plants will prevent this problem, too," Shaft says.

Spider mites and aphids can also be removed with water, perhaps with a little soap in it.

When pruning after the plant has greened out, cut one-fourth inch above the spot where a five-leaf bunch comes out.

Fertilize up until August with a 10-10-10 or 20-20-20 fertilizer. Shaft suggests, "Mix a cocktail of granular, liquid and slow release. In spring I also put Epsom salts on the soil around the plants to develop the roots. It also helps the plant take up other nutrients."

Larger plants take ¼ - ½ cup Epsom salts per plant. Miniatures require one or two tablespoons.

Japanese beetles have been a big problem with roses, particularly this year. They seem to like the taller roses and certain lighter colors.

To get rid of them, pick them off and put in a container of soapy water and then dispose of them. Chemicals like Sevin, Merit or Bayer will also work but Shaft likes to avoid chemicals when possible.

She suggests a mixture of six eggs and water, mixed well in a blender. Let the mixture settle out and then put it in a sprayer and apply to the plants. It works to discourage insects and deer.