Ten tips for growing great garden roses
Story by Hugh Conlon
Roses (Rosa spp.) contribute beauty and fragrance to any garden. There are many varieties of roses to pick from, many wanting little extra care. To get your roses off to a great start, plant them in the right spot and select the best varieties. Rose breeders continue to introduce varieties that are more resistant to pest and disease problems.
Here is a step-by-step “recipe” for growing roses. Steps one through five are of critical importance if you want to avoid lots of extra care in years to come. Follow steps six through 10 on a timely basis and your roses will flourish.
1. Choose Good Genetics – Buy only the best rose varieties (cultivars). Hybrid teas, floribundas, grandifloras, and shrub roses are the four most popular categories of roses for Southeast gardens. Discussions of other types of roses – such as miniatures, tree standards, and climbers – are not included here. Visit reference rose gardens near where you live to learn the best rose cultivars for your area. See sidebar below.
2. Location, Location, Location – Roses grow and bloom their best in full sun with moist, well-drained soil that is rich in organic matter. “Ideal sunlight” is from sunrise through early afternoon. Roses require a minimum of six hours of direct sunlight daily. The more shade, the fewer flowers. Roses desire a slightly acid soil –pH 6.2 to 6.5. Apply ground limestone (either hydrated or dolomitic) to raise soil pH or powdered sulfur to lower pH. Amounts to apply will be indicated on your soil test report. Fall is the best time to apply lime or sulfur, as nutrients will work down into the soil over the winter.
3. Bed Preparation – Proper siting and soil preparation goes a long way toward disease management. The location should allow good air circulation and not be surrounded by tall landscape plants. If soil drainage is questionable, consider growing roses in raised beds that are at least 6-8 inches tall and sitting atop gravelly soil base.
4. Planting and Planting Depth – Improper planting depth is a common landscape mistake. Do not plant rose plants too deep and avoid over-mulching, which simulates excessive planting depth. Consider planting roses in the fall rather than spring.
5. Never Crowd Roses – The foliage of rose bushes should not touch that of adjacent plants. For disease and insect prevention, good air circulation and capturing all of the sun’s rays are imperative. Better yet, leave at least 10-12 inches between plants. Information on the plant tag regarding height and spread is usually incorrect, generally undersized.
6. Pruning and Deadheading – Develop an open-centered or vase-shaped shrub. Prune in late February or March, reducing plant height and spread by two-thirds on most shrub types. Prune hybrid teas and grandifloras to a height of 18 inches. Prune smaller-growing shrub-types such as Drift and Flower Carpet series less, maybe 25-33 percent growth reduction. Prune again in mid to late July, cutting back one-third the plant’s height. In addition, eliminate some interior older wood on 3-year-old and older roses. Deadheading during the growing season leaves less pruning to perform in late winter and late summer. Roses can provide five to seven nice flowering cycles annually with timely pruning/deadheading.
7. Mulching – Organic mulches are best for roses. Maintain a minimum of a 2-3-inch layer of pine straw or pine bark at the start of spring. Over time, pine bark mulch tends to acidify and hardwood mulch raises soil pH. Do not pile mulch around plants. Fine or aged bark and/or wood chips will necessitate extra nitrogen fertilizer to be applied.
8. Fertilization – Following late winter pruning, apply a three-month-rated, controlled-release fertilizer at the rate of 1 (established bed) to 2 (new beds) pounds of actual nitrogen (N) per 1,000 square feet of bed area. Higher rates may be needed for new beds and those showing low levels of fertility. Once annually, phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) levels should be applied to rose beds (amounts determined by soil testing). Fertilize after the late summer pruning at one-half the spring season application rate. An alternative method is to feed with water-soluble fertilizers through the growing season. Roses don’t need fertilizing during June and July. If a soil test report diagnoses magnesium deficiency, use Epsom salt (magnesium sulfate), available at most local pharmacies. Epsom salt will improve leaf color and promote new cane growth around the shrub base.
9. Insect Management – Aphids, Japanese beetles, eriophyid mites, and flower thrips are the major pests of a rose garden early spring through late summer. Consult with your state land grant university website or county extension office for pesticide recommendations. Spinosad, horticultural oil, acephate, and many other contact and systemic insecticides should provide a good management care.
10. Disease Management – In general, modern rose varieties are more disease resistant. In your search for the “perfect rose,” always select varieties that are highly resistant to blackspot and cercospora leaf spot diseases.
Four Top Rose Gardens In The Southeastern U.S.
• The University of Tennessee Gardens – Knoxville, Tennessee
Visit UT Gardens online here
• Biltmore Estates – Asheville, North Carolina
Visit Biltmore online here
• Birmingham Botanical Gardens – Birmingham, Alabama
Visit Birmingham Botanical Gardens online here
• Ag Center Botanic Gardens at Burden – 4560 Essen Lane, Baton Rouge, Louisiana
Visit the Botanic Gardens at Burden online here
THE TOUGH CROWD
Roses highly resistant to blackspot and cercospora leaf spot*
Resistant cultivars (<2% foliage infected)
Blushing Knock Out (‘Radyod’)
Brite Eyes (‘Radbrite’)
Double Knock Out (‘Radtko’)
Pink Double Knock Out (‘Radtkopink’)
Pink Knock Out (‘Radcon’)
Knock Out (‘Radrazz’)
My Girl (‘BAIgirl’)
Wildberry Breeze (R. rugosa ‘Jacrulav’)
Moderately resistant (<10% foliage infected)
Carefree Sunshine (‘Radsun’)
Como Park (‘BAIark’)
Forty Heroes (‘BAInial’)
My Hero (‘BAIhero’)
Super Hero (‘BAIsuhe’)
Wild Spice (‘JACruwhi’)
*UT Resistance Screening Program Of Garden Roses (2006-2012)
Common Rose Diseases
Foliar diseases: Black spot, cercospora leaf spot, downy mildew, powdery mildew
Stem diseases: Botrytis blight, canker, crown gall, dieback
Root diseases: Phytophthora root rot
Systemic diseases: Rose mosaic virus, rose rosette virus (pictured below)