Introduction
Colorful and fragrant Hardy Shrub Roses (HSR) are growing in popularity as gardeners discover they can be planted almost anywhere you would plant a shrub.  They come in all rose colors and have the appeal of Hybrid Tea Roses (HTR) without the high maintenance requirements.  Bloom patterns vary from one-time bloomers to repeat bloomers (bloom in spring and fall) to continuous bloomers. Most shrub roses have excellent floral quality and are winter hardy and highly disease resistant.  They typically grow from 2-6’ tall and can be trained to grow as a hedge or climber. 

Site
Light – Shrub roses need full sunlight.  If receiving less than 6 hours of sun each day, they will be leggy, have few flowers, and are more prone to diseases.  The best location is a southeast exposure that receives afternoon shade since dew remains on the leaves longer with morning shade promoting disease.  Good air circulation around the plant is also necessary to reduce incidents of disease.

Soil – Shrub roses thrive best in well-drained soil.  Work peat moss or sand into the soil before planting to improve drainage.  They prefer a slightly acidic soil with a pH range of 6.0 -7.0.  Shrub roses in alkaline soils with a pH near 8.0 will develop chlorosis, a yellowing of the leaves.

Planting
When – Bareroot roses should be planted in early spring while still dormant.  Potted roses can be planted anytime during the growing season; however, spring planting allows the roots to become more established before winter.

How – Prepare the soil before planting by working about 4” of hummus into a 9” radius around the hole.  Shrub rose roots can extend 2’ so work the hummus to this depth.  The hole should be about 1½ times as large as the spread of the roots. For bare root plants, remove from the package immediately, trim damaged roots or canes, and soak overnight.  Trim excessively long roots rather than twisting them around the hole.

 Make a cone of soil in the hole’s center and spread the roots out over the cone.  Cover the roots with a mix of one part organic matter to four parts soil.  When the hole is half full, tamp the soil to eliminate air pockets.  Finish filling the hole with the soil mix, then water thoroughly and fertilize with a starter solution (read and carefully follow the starter fertilizer directions).  Prune the canes to 6-8” to encourage basil bud breaks and create a bushier plant.  Mound 6-8” of soil around the dormant plant until the buds break, usually in 14 days.  When buds break, gently wash the mound away with water.  Potted plants should also be soaked in their container and left to drain overnight. To avoid root disturbance when planting, cut out the bottom of the container and slit the container’s side to carefully remove it from the rose.  If the root ball is a dense mass, make shallow cuts in several places down its side to encourage new root growth.  Plant the rose so the soil from the pot is level with the ground soil.  Water thoroughly and fertilize with a starter solution.

Spacing – Shrub roses may be much larger than Hybrid Tea Roses so space plants according to their mature size.  Plants that will reach 6’ when mature should be spaced 6’ apart when used as individual specimens, closer if part of a hedge. 

Care
Watering – Roses require lots of water.  The common rule of thumb is one inch of water per week during the growing season.  This is especially important during the first growing season of a newly planted rose.  Light, frequent watering is not recommended.  Instead, thoroughly soak the soil to a depth of 15-18” once a week.

Mulch –Mulching helps retain soil moisture, keeps the soil temperature cool, decreases erosion, and reduces weeds.  Using 2-3” of wood chips, straw, or grass clippings (not treated with chemicals) improves the soil as breakdown and decay occurs.  During decomposition of the mulch, large amounts of nitrogen can be bound up so additional applications of nitrogen may be necessary.  Wet the soil before you apply the mulch to prevent the mulch from absorbing the soil’s moisture. 

Fertilizer – Fertilization programs vary depending on the type of rose.  Generally, apply no fertilizer the year of planting; begin the following year.  Spread the fertilizer in a band at least 6 inches from the plant’s roots, work it into the soil, and water thoroughly.  One application of a balanced fertilizer in early spring is adequate for Species Roses.  All other types should get a second application at the completion of spring bloom.  To encourage repeat flowering, a third application can be applied in late July.  Do not fertilize after August 1 because it will promote new growth and delay cold hardening.

Weeding – Pull weeds in the crown of the plant by hand.  Mulch will reduce weed growth.

Deadheading – Deadheading spent rose flowers discourages the formation of rose hips and encourages the continuous flowering of roses.  Deadheading also gives the plant a cleaner appearance and allows it to maximize its vegetative growth.  Stop deadheading after October 1 if you want to take advantage of the fall hip display.

Winter Protection – Some winter injury is expected.  After three years of winter injury observations at the Minnesota Landscape Arboretum, even the hardiest of roses exhibited some cane injury.  Water plants well in the fall after the leaves have turned but before the ground freezes.  In windy locations, provide a barrier on the windward side to keep shoots from drying.  After a hard killing frost, remove all dead or diseased canes and leaves, rake up all debris, and mound the new plant with whole leaves, straw, or evergreen boughs.

Pruning – Shrub roses need little pruning although it is best to remove dead and unhealthy branches.  Removing older canes also opens the center of the plant for new cane formation and improves air circulation.  Up to one third of canes can be removed each year.  Prune at a 30-45º angle ¼” above an outward facing bud eye.

Problems
Recommendations for pesticides change constantly.  To keep up with recommendations, obtain current information from the University of Minnesota Extension Service.

Insects – The most common insects observed over a 4 year study at the Minnesota Landscape Arboretum were aphids, mites, rose stem borers, and gall wasps.  Occasionally leaf miners, leafhoppers, and thrips were noticed.  Properly diagnose and treat insects.  Aphids are best controlled with pesticide.  Light infestations of mites can be washed off with a garden hose.  Remove galls to control wasps, and remove infected canes to control rose stem borers.   Removing nearby wild roses also helps control some insect problems.

Diseases – Many shrub roses are disease resistant.  If susceptible varieties are planted, one must either carry out a spraying program or accept blemished roses.  The most common and noticeable diseases are foliar including block spot, powdery mildew, leaf spots, and rust.  Black spot is recognized by raised, purplish spots on the canes and remains on infected plants over the winter.  Powdery mildew, seen as white, powdery patches, causes leaves to fold inward and become distorted.  To reduce diseases, prune out diseased canes in early spring, rake up fallen and yellowed leaves, provide good air circulation to diminish the accumulation of dew on the leaves, and water plants near the roots to eliminate the splashing of disease organisms.

Additional Information
For more information, refer to the University of Minnesota Extension Consumer Horticulture webpage at http://www.extension.umn.edu/ConsumerHort/

Sources
Hardy Shrub Roses may be purchased at local garden centers and nurseries or through mail order sources. Local sources may supply plants more adapted to local growing conditions and plants may be in bloom so colors may be observed. Mail order sources may offer mo re variety and most ship dormant, bare root plants.  Plants on their own roots are longer lived and will only produce genetically true canes.

Thank you to the individuals and businesses who have contributed to the Hardy Shrub Rose Garden by donating plant materials, time, or funding.  This list is informational only and does not represent an endorsement by the University of Minnesota.