Roses

H-118 (Revised), August 1993
Reviewed and reprinted April 2005

Robert G. Askew, Extension Horticulturist, Emeritus
Ronald C. Smith, Extension Horticulturist

Introduction

THE MOST POPULAR ROSES GROWN -- hybrid teas, grandifloras and floribundas -- are not fully hardy in northern areas. Short, hot summers and long, cold winters mean that more care is necessary, but these quality roses can be grown in North Dakota.

Choosing a good location for your rose bed is important. Roses should have a minimum of one-half day's sun, but will do better with two-thirds to full sun. A little shade in the heat of the afternoon helps prolong the life of the blooms. Roses should be grown in good garden soils. The addition of organic matter, such as peat or well-rotted manure, will improve the growth and vigor. Choose an area of well-drained soil. Roses won't withstand wet, soggy soil.

Planting and Summer Care

When to plant roses may depend upon whether you buy bareroot dormant bushes or potted plants that are already growing and sometimes even in bloom. Plant dormant bushes early, before trees and shrubs leaf out in the spring or at least by early May. Do not plant growing potted roses that were started in a greenhouse until danger of severe frost is past, that is, late May or early June. When planting dormant, bareroot roses, trim the broken ends of the roots to provide a nice clean cut. Preserve as much of the root system as possible.

How you plant roses is vitally important for winter survival. Dig a hole large enough to hold the entire root system of either potted or bareroot plants without crowding, and deep enough so that the graft (a distinct knobby joint on the stem between the branches and the root -- see the drawing) is 1� to 2 inches below the soil surface. Planting at this depth is very important in cold climates regardless of other instructions you may have read.

Place the plant carefully in position and put loose friable soil around the roots and firm with your hands. Water well. If plants are dormant, mound up loose soil to a height of 10 to 12 inches above the normal ground level to protect the stems from frost and drying. Do not remove this mound of soil until the plant is growing vigorously. Rains and hoeing will gradually level the soil mound during May and June.

The nursery usually has pruned the bushes you buy. If not, shorten all the canes of bareroot plants to 8 to 12 inches and cleanly cut off broken stems and any thin, weak branches. On over-wintered bushes of hybrid tea, grandiflora and floribunda roses, remove all dead wood (detected by dark or obviously discolored bark) as well as broken or weak branches. Make each cut � inch above a live, healthy leaf bud on the outside of the bush to make your plant broader and without crowded stems.

When removing spent blooms or using the roses as cut flowers, cut the stems down to � inch above the first leaf that has five leaflets. Shoots arising from the bud in the axil of the five-leaflet leaf will be more likely to flower than shoots from the buds in the axils of one- or three-leaflet leaves.

Summer watering is important if you expect your roses to continue blooming when rainfall is insufficient. Roses require about 1 inch of water each week. All hybrid tea, grandiflora and floribunda roses are capable of repeated bloom with proper care. To avoid damage to the flower and splashing of disease spores from the ground to foliage most rose growers prefer to water by soaking only the soil rather than overhead sprinkling.

Proper fertilization will help the plants produce more and larger blooms and will shorten the rest periods between flurries of bloom. Complete fertilizers, such as 5-10-5. 10-20-10 or a commercially prepared rose food, are all satisfactory. Fertilizers are best applied in early spring (late April) and again when the plants approach their peak flowering (mid to late June). Stop fertilizing by August so that your rose bushes will have a chance to slow their growth and mature tissues before winter. Most lawn fertilizers contain too much nitrogen and should not be used for roses.

Chlorosis (an unnaturally early or mid-season yellowing of the foliage with the veins usually staying darker green) is most often due to an iron shortage caused by poor drainage or excess lime in the soil. Avoid such sites or build up your rose bed to improve surface drainage. Acid peat mixed with soil at planting time will counteract some of the excess lime. Finally, you may wish to consider applying one the chelated irons (Versenol or Sequestrene 338) according to the manufacturer's directions.

Insect and Disease Pests

Insect pests include the rose curculio (a reddish-brown "snout-beetle" that causes dried-up buds), leaf cutter bee (it cuts circular pieces from the leaves), aphids (plant lice), and spider mites. Most all-purpose rose dusts or sprays include insecticides for control of these pests. Systemic insecticides such as Di-Syston (an ingredient in many rose dusts) which can be applied to the soil at planting time should give aphid and mite control for two to five weeks A regular program of spraying or dusting (weekly and after each rain) is best to keep these pests from getting started.

Common rose diseases include black spot, dark circular but somewhat fuzzy spots on the leaves (which later yellow and fall prematurely), and mildew, a soft gray-white film on the leaves that causes them to curl or twist slightly. Both these diseases grow most rapidly in warm, humid weather or wherever air movement (wind) is poor near your rose bed. It is important that the leaves on roses dry as soon as possible in the morning after heavy dews. Wet foliage increases disease problems. The best control is prevention through a regular program of spraying and dusting with fungicides such as those found in the all-purpose rose dusts. Weekly spraying or dusting from June until frost is recommended, as well as after periods of rain.

Roses for North Dakota

Winter protection for roses can begin with allowing the last blooms to remain on the bush to form hips (seed pods). This naturally slows the vegetative growth cycle down, bringing the plant in to the initial phases of hardening off for the coming winter months.

Remember that most named varieties of roses are propagated by grafting the variety upon a standard rose rootstock. If the graft union is protected by deep planting, there will be a better chance for winter survival of your rose variety when it is mulched. Plant the graft 1� to 2 inches below the normal soil surface. In some cases, the planted variety (the plant portion above the graft) winterkills followed by the growth of the rootstock in the spring. The rootstock usually grows vigorously but seldom produces any flowers. If you want the original variety, you will need to repurchase and replant again. Be sure your roses have sufficient moisture to carry them through the winter. If the fall has been dry, soak them in late October. In early November, shorten the stems to about 18 inches. Then mount each plant 6 to 8 inches high with soil, shavings, vermiculite or sand. Next, place 10-12 inches of leaves or coarse hay on top. Use tree branches or chicken wire to keep leaves in place as well as to hold snow.

Leave the mound intact until mid-April when you take it off in stages. If you have only a few rose bushes, it may be easier to collect dry leaves in large plastic garbage bags. Store the bagged leaves until about the first of November, then merely mulch your roses by carefully placing the closed leaf-filled garbage bags tightly against each bush for mulch. Two bags will adequately protect each rose. In the spring the bagged leaves may be used for compost. When the mounds or bagged leaves are finally removed in the spring, finish pruning by removing all dead wood (dark and discolored) as well as injured or small, weak stems. Your roses should then be ready for another season.

Many varieties of roses are available and new introductions are made each year. The following have proved popular:

Hybrid Teas

• Bing Crosby -- persimmon-orange
• Charlotte Armstrong -- rose-red
• Chrysler Imperial -- rich red
• Color Magic -- deep pink
• Crimson Glory -- deep red
• Double Delight -- cream-white, brushed with rich red
• First Prize -- pink
• Helen Traubel -- pink
• Honor -- white
• John F. Kennedy -- white
• Lowell Thomas -- yellow
• Mirandy -- wine-red
• Mr. Lincoln -- red
• New Yorker -- bright red
• Pascali -- white
• Peace -- cream-yellow with pink blush
• Royal Highness -- pink
• Sterling Silver -- silver-lavender
• Tropicana -- coral-orange

Grandifloras

• Arizona -- copper-gold
• Camelot -- coral-pink
• Carrousel -- bright red
• Love -- red and white bicolor
• Montezuma -- coral-orange
• Queen Elizabeth -- medium pink
• White Lightning -- white

Floribundas

• Circus -- gold-red bicolor
• Europeana -- red
• Eutin -- bright red
• Fashion -- golden-salmon
• Garnette -- small, deep red
• Ivory Fashion -- clean ivory
• Red Pinocchio -- medium red
• The Fairy -- light pink
• Vogue -- coral

H-118, August 1993
Revised and reprinted, April 1995