Sunday, October 30, 2011

Care and Maintence: Grandiflora Rose Variety

In 1954, in honor of Queen Elizabeth, Grandiflora roses were created by crossing hybrid tea roses and floribundas. They are a tall and vigorous hybrid with large flowers and long stems that grow in clusters. They are popular but ironically, in England aren't even recognized as a distinct variety. There are several varieties and newer strains tend to be shorter and more compact than the older varieties. The care for grandifloras is similar to that of hybrid tea roses. Compared to most roses, they need a bit more attention including watering, fertilizing and in some cases, fungicide.

Proper pruning of these roses can result in a healthier bush with more abundant blooms. Prune rather severely in January or February.
  1. Prune most aggressively in late winter, when the plant is dormant--all the leaves have dropped off, and there are no visible signs of growth. At this time you should remove all dead or diseased wood. Keep in mind to cut canes above a bud slanting away from the bud.
  2. Remove any canes that are touching or crossing each other, and prune out twigs and branches from the center of the bush to allow light and air to circulate.
  3. Cut canes back to a height of 18 to 24 inches. From new canes, prune off only one third. If the bush is very dense with canes, thin them out, using pruning shears remove all but 5-8 of the oldest canes, leave more on vigorous shrubs. If the canes are thick, use lopping shears or a pruning saw.
  4. Prune gently during blooming and growing season. Shape the plant by cutting back depending on what you want the bush to do. Look at the leaflet clusters. Rose leaves usually cluster in groups of 5 and 7. Each type of cluster results in a somewhat different growth patterns.
  5. Cut for new blooms. Dead head flowers down to the next leaf with 5 leaflets. If you want to stimulate blooms, cut the rose branch at a 5-leaflet cluster. Prune about ¼-inch above where the leaf stem meets the branch--the new bud is tucked in there. The resulting branch will be shorter and bloom sooner.
  6. Cut for new branches. If you want to stimulate new branch growth (which will result in new blooms at the end, but it will take longer) cut the rose branch at the 7-leaflet cluster. Prune about a ¼-inch above where the leaf stem meets the branch--the new bud is set in there.
  7. Keep an eye out for die back ( when branches turn yellow or black, and then die) or diseased wood. This can happen throughout the season and should be removed in a timely manner.
  8. Clean up all debris and dispose of properly to avoid pests and disease gathering on the trimmings.
Pruning Tips:
  1. When pruning, always prune at an angle to prevent saturation on the open wound of the branch. This helps it seal more quickly.
  2. Seal the open cuts on shrubs and bushes to minimize infection. Consider using water-based Elmer’s glue.
  3. Don't spray water on the bush immediately after pruning; you may increase the risk of infection on the cut because it literally is open. Give the wound a few hours to seal over.
Appearance and Description
  1. Grandiflora roses tend to be taller bushes, often growing up to 6 feet, and are usually characterized by clusters of large flowers on long stems.
  2. With proper care, they bloom almost continuously from late spring to autumn.
  3. The aromas and scents from them can be described as “sweet tea”
  4. Petals per bloom: 30
  5. Bloom size: 5"
Location
  1. Zones 5-10
  2. Plant in fertile, well-drained soil
  3. Roses prefer a neutral to slightly acidic soil
  4. Plant where roses receive sun for 6 hours or more
  5. Air circulation is important
  6. Space 3-5 feet apart
  7. Eastern exposure is beneficial
Watering
Roses require more frequent watering than most other landscape plants.
  1. During the cool winter months, water roses once a week or when needed.
  2. In spring and fall, loam soils are usually irrigated two to three times per week.
  3. During the summer heat you will probably need to water three or four times per week (3-4 gal./plant). You may have to water every day, depending on soil and weather conditions. (Clay soil retains more moisture than sandy soil. Loam soil is between clay and sand.)
  4. Allow the soil to dry out between waterings, but don’t allow the plant to become stressed.
Fertilizing
Roses need frequent applications of a slow-release fertilizer
  1. The first application of slow-release fertilizer should be applied after the roses have been pruned in January or February and repeated every six weeks until June.
  2. Roses can be given a break during the hot summer months with no fertilizer applications. Then start the slow-release fertilizer again in September, with the last application around mid-October.
Planting roses
  1. Follow planting guide from the providing nursery
  2. Be sure the bud (graft) union is just below soil level
  3. Select healthy plants, if packaged or bare root plants are dry, immerse in water for a few hours.
  4. Container roses can be planted year-round.
Preventative Care and Maintenance
  1. Deep water to a depth of 2 feet throughout the growing season.
  2. Hose off roses regularly with water. Spray in the early morning before the sun gets hot to decrease chances of leaf burn. Spray the underside of the leaf. This will keep the roses clean, increase the surrounding humidity, and will help to control insects before they can cause any damage.
  3. Use a forceful water spray to eliminate aphids and spider mites.
  4. Roses slow down during hot months and produce smaller and fewer blooms. Remove spent blooms by cutting back to the first five-leaflet set. Leave as much foliage as possible, which will help to shade the bush.
  5. Shade the trunks of tree roses during hot summers to prevent sunburn. Painting the trunk with white tree paint or covering the trunk with cardboard or shade cloth will also help.
  6. Watch for sucker growth on grafted roses. These are canes that come from below the bud union. They appear different from the other canes. Cut them off below the bud (graft) union.
  7. Seal all pruning cuts with a good wood glue to prevent cane borers from entering. The borer larva eats the stem center and the infested cane grows poorly or dies. Cut back the injured cane an inch at a time until you find healthy wood.
  8. Learn to recognize Lady Beetles, Lace Wings and other beneficial insects in all stages of their lives (egg, pupa, adult).
  9. Check roses on a regular basis to identify potential problems.
  10. At the end of the growing season, slow down the plant growth and allow the plant to harden off by leaving the rose hips on the bush after the last blooming cycle.

Diseases
Grandifloras are resistant to powdery mildew.
Diseases and pests to look for include

Aphids
  1. Suck on new growth and buds starting early spring
  2. Control with forceful spray of water or spray with soapy water, repeat daily to control population if necessary
  3. Beneficials: lady beetles and green lacewings
Spider mites
  1. Small, on leaves
  2. Sometimes webbing
  3. Hot, dry weather
  4. Often increase in numbers if a broad spectrum pesticide killed beneficials
  5. Damage to buds cosmetic
  6. Strong stream of (soapy) water
Thrips
  1. Damage on petals
  2. Thrips in new buds
  3. Damage mostly cosmetic
Cane borer
  1. Tunnels into canes soon after winter pruning -- seal prune wound with Elmer's Glue immediately after pruning
  2. If a hole is present in prune wound, cut back until cane is healthy
  3. Use wood glue to seal wound if desired
Leaf cutter bees
  1. Circular leaf cuts
  2. Damage only cosmetic
Crown gall
  1. Caused by Agrobacterium tumefaciens
  2. Infects through wounds
  3. Plant gradually declines as gall develops at base of plant
  4. Remove and destroy infected plants
  5. Don’t replant roses in this soil
Rose mosaic virus
  1. Spreads only through infected stock
  2. Not transmitted through pruners or shovels
  3. Weakens plant over many years
  4. No cure
Salinity
  1. If soil salinity is too high, excess salts cause leaf injury and dieback.
  2. Remedy by leaching with sufficient irrigation water to push salts below the root zone.
Nutrient deficiencies
  1. Optimum pH for roses is 6.0 - 6.5
  2. Iron deficiency – leaves yellow between the green veins, apply chelated iron
  3. Nitrogen deficiency – old leaves yellow first, spindly growth, small and few flowers, fertilize according to package instructions
  4. Magnesium deficiency – Edges of old leaves turn yellow, apply magnesium sulfate (epsom salt) to rose bushes  

    The Arizona

1975 AARS Rating: 5.8
Classification: Grandiflora
Fragrance: strong tea
Flower description: orange blend, double blooms, 30-35 petals
Foliage color and growth habits: bronze green, semi-glossy, 4'-6'