Growing Roses In Pinal County

Roses are always a popular flower and this year has been a good year for the colorful flowers.

Roses have many uses in the landscape.  Miniature roses in pots by the front entry, long-stemmed hybrid teas along a foundation, climbers trained over a shady trellis, or a massive color display from cascading canes filled with blossoms are just some of the opportunities that await.  The huge diversity of rose cultivars offers an almost limitless number of landscape possibilities.

Can roses do well in the desert?  The easy answer to that question is absolutely yes!  However, you do have to know what you are doing.  If you are just getting started, though, do not dismay.  When you know a few basic rules, you can still grow a beautiful rose, and then learn as you go.

Roses come in many forms.  One type are the old rose cultivars, ancestors of the modern, large-flowered varieties that we enjoy today.  These heirloom roses have been planted for centuries, but now are found mainly in the gardens of big time rose enthusiasts and in museums.  You may be interested in searching out and planting one or more of these types.

Most people, however, are attracted to the modern rose varieties.  Even still, the selection process can be daunting.  A gardener can select from hybrid teas, climbers, miniatures, floribundas, and grandifloras, to name a few.

Floribundas and polyanthas have gained in popularity in Arizona.  Both produce flowers in clusters.  The floribundas are known for their vigorous growth and profusion of medium to large blossoms.  These plants are very hardy and many varieties bloom almost continuously.  The polyanthas are small-growing bushes with clusters of small flowers and generally are not as hardy as floribundas.

Grandifloras are generally vigorous and tall growing.  The flowers are similar in form to those of the hybrid teas, but are usually borne in clusters, similar to the floribundas.  One benefit of grandifloras is that they have stems long enough for cutting and arranging. 

Hybrid tea roses are among the most popular roses grown in Arizona.  They provide excellent cut flowers, and in the warmer sections of the state, provide vibrant spring and fall color.

Before the hybrid teas arrived on the scene, the hybrid perpetual roses were the most popular roses.  The flowers are large and showy and the plants are vigorous and cold hardy.  Their main period of bloom is in the spring, but some varieties will produce flowers again and again through the growing season.  Hybrid perpetuals need a little more fertilizer and water than the teas.

Climbing roses may be either hybrid teas, hybrid perpetuals, floribundas, or rambler varieties.  All of these have long canes and need special handling.  The flowers may be borne in clusters or on single stems, depending upon the variety and method of training.

Miniature roses are popular because of their colors and smaller blossoms.  They can provide a unique appearance in the landscape that gives both grace and color.  Miniature roses are also well-adapted to container culture.  Limited space allocations make them ideal for patio and townhouse gardens. 

Miniature roses respond to the same basic cultural practices as standard-sized roses but because they are smaller, fertilizer applications should be scaled back accordingly.  Good foliage and bloom capabilities can be maintained by cutting back one-third to one-half several times during the season just after the peak bloom.

Aphids and thrips are the most common pests of roses in southern Arizona.  Aphids are soft-bodied insects that feed through sucking mouthparts and cause small dots of yellow tissue, called stippling, where they feed.  Soap solutions, washing with strong streams of water, and systemic insecticides work well in controlling these insects. 

The thrips insect is the main culprit in causing petals to turn brown along the edges and prematurely drop from the flower.  Thrips are most easily controlled with a systemic insecticide. The quarter-inch long, black, cigar-shaped pollen beetle which is so common in area rose blossoms feeds mainly on plant pollen and is not generally responsible for damaged blooms.

Circle- or oval-shaped pieces of missing leaf tissue that seemingly disappear overnight are the result of the work of leafcutter bees.  These are solitary bees, meaning that they do not form community hives.   Each female cuts and uses the leaf segments to form brood cells in which her eggs develop into adults.  Because neither the bee nor her offspring eat the plant tissue, no systemic insecticides will ever touch the animals.  Contact sprays do not work well either because the bee works so quickly that by the time the insecticide is located and aimed, the damage is done and the bee is gone.

The best solution for leafcutter bees is to diligently search out and destroy the cigar-shaped, one inch long nests before the new adults hatch out.  This will help reduce the total population of bees in the area.  Fortunately, the tissue lost to leafcutter bees is usually not sufficient to damage the health of the plant.

Good plant nutrition is critical for rose health.  Roses, like all plants, need sufficient amounts of the sixteen essential nutrients.  Of these, nitrogen is the one element that requires the most attention.  Our low organic matter soils simply cannot provide sufficient nitrogen on a regular basis to allow a plant to grow and produce normally. 

Nitrogen-based fertilizers should be applied lightly and frequently for best results.  It is better to apply small amounts of fertilizer once each month during the growing season, starting in January and ending in October, rather than a single heavy application once a year.  An application of about two ounces of 21-0-0 or 16-20-0 every six weeks during the growing season starting in early February and ending in mid-October is best for most Pinal County areas.  Two ounces corresponds to about two heaping or four level tablespoons of material.  If you use a phosphorus fertilizer, make sure to work it into the ground with a rake or hoe because phosphorus will not leach into the soil during an irrigation as will nitrogen.

Another key to good rose production is to make sure that the plant gets plenty of water on a frequent basis, especially during the hot, dry summer months.  Deep irrigations that wet the entire root zone will also help leach our harmful salts.  Covering the surface of the soil underneath the bushes with an organic or stone mulch helps slow evaporation and keep the soil cool.

When blossoms are cut from the plant, it is important to use a sharp tool, like a knife, pair of scissors, or pruning clippers.  The cut should be made at a 45 degree angle and just above a node, the point where leaves emerge from the stem.  This will avoid unsightly stub ends on the stems and make it easier for the plant to grow new tissue from the buds located at the node.  Old flowers should be removed, “deadheaded,” promptly to encourage the growth of new blossoms.

Finally, roses like a neutral to slightly acid soil, not the alkaline soils native to the desert.  Regular additions of soil sulfur to the soil will help bring down the pH to a level that will allow the rose plant to tolerate our unfriendly conditions.

With a little know-how and patience, roses can bring lots of color to your landscape.

If you have questions, you can reach one of the Master Gardeners at the Cooperative Extension office, 820 E. Cottonwood Lane, Building C, in Casa Grande.  The telephone is (520) 836-5221, extension 204.

The University of Arizona is an equal opportunity, affirmative action institution.  The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

Rick Gibson

Extension Agent, Agriculture

University of Arizona Cooperative Extension

820 E. Cottonwood Lane, Building C

Casa Grande, Arizona 85222

Voice:  (520) 836-5221

Fax:     (520) 836-1750

email:   gibsonrd@ag.arizona.edu