Regional Growing Guide: Southwestern Deserts
From the sunny beaches of California to the blistering deserts of the Southwest, this region is marked by nearly year-round sunshine and little rain. Roses bloom from April through December in the more temperate parts, while they take a rest during August and September in the great deserts, where searing temperatures vary little between day and night. There, roses have two seasons: spring and fall, with peak blooming in April and October. Ample irrigation is key. Soils may be alkaline or sand: it's important to amend with plenty of organic matter. The best roses are heat tolerant, and tend to bear darker leaves and bloom in more intensely saturated colors.
Select a season: Spring Early Summer Late Summer Fall
Roses in Summer
Roses are quite fuss-free in the low desert, adding color and fragrance to our gardens and supplying beautiful cut flowers. Even though summer is our most difficult season for roses, you can help them thrive by watering effectively and maintaining sufficient soil moisture.
Watering Efficiently
The most important thing is to monitor their water needs carefully. Depending on your soil type, temperature, elevation and rainfall, it will probably be necessary to water two to four times per week in summer. Clay soil will retain more moisture than sandy soil so it requires less frequent watering. Whether using drip irrigation, flood irrigation, or a hose, water should soak 18 to 24 inches deep. This ensures that the entire root system gets moistened.
Prevent Salt Burn
Deep watering also helps prevent salt burn. Salt burn is common in the Southwest because of our low rainfall, alkaline soil, and water supply that is high in salts. Salts dissolve in water and move with it as it soaks through the soil. Wherever the water stops penetrating, the salts will stop also. Frequent, light sprinklings or short periods of drip irrigation allow salts to build up in the top layer of soil, where the roots are. Excess salt accumulates in the leaf edges, where it kills the tissue and the leaf dries out and turns brown. Browning usually occurs on older foliage first. Sometimes salt burn is mistaken for a lack of nutrients and more fertilizer is applied, which worsens the situation. Once a month, leach the salts well below the root system with a slow, deep watering.
Mulching
Add 4 to 6 inches of mulch around the base of your rose bushes. Compost, manure, bark chips, grass clippings, coffee grounds, pine needles, whatever you have available. Mulch retains soil moisture, reduces soil temperatures so roots aren't in such hot soil, and inhibits weeds. As the mulch breaks down, it adds organic matter and nutrients to the soil.
These simple watering and mulching chores will help your roses get through the summer and head into fall ready for their second major bloom period.