Phoenix has two growing seasons. The first is from mid-February through the end of May, and the second growing season is from September to mid-November. January is Phoenix's only winter month. Summer heat can be brutal to roses. For the avid gardener, summer is like the desert's winter, as most plants are near dormancy due to the heat. Understandably, gardening calendars are unique to this area.
January is the best time to plant bare-root roses; roses are dormant during this month, and mid-February marks the beginning of the growing season. Plant bare-root roses so that they are established before the brutal heat of summer transcends upon them (summer begins in May in Phoenix.)
Container-grown roses can be planted practically year round, due to their established root system--although it is best to avoid planting them during the summer months. Temperatures begin to cool down in September, which is also the start of the second growing season. If you are going to plant roses during September, wait until the night temperatures fall into the 70s. In October, as the weather cools down even more, nurseries will be filled with container-grown plants, including roses.
Summers in Phoenix can bring triple-digit heat and scorching winds, presenting a real challenge to growing roses. However, if you follow some basic procedures, your roses will survive and prosper in this extreme desert climate.
According to Marylou Coffman, a Gilbert, Arizona rosarian and All-America Rose Selection Committee judge, "If there's a problem with your roses, nine times out of ten, it's related to water." Remember to water often and deep. During the hottest months, Coffman suggests watering at least three times a week (using at least 3 to 4 gallons of water per plant during each watering.)
It is very important to mulch in order to keep the roots of the rose cool, and keep moisture in the soil. Mulch also helps to keep weeds to a minimum, and enriches the soil as it decomposes.
Your roses will need some afternoon shade during the incredibly hot summer months. If this isn't possible, spray your plants down two to three times a week. Spraying increases the humidity and cools down the plant's leaves.
A regular fertilizing program will produce strong plants with beautiful blooms and glossy leaves.