Answer: There are two distinct growing seasons in the low desert with different annual vegetables and flowers thriving in each season. There's a cool season from approximately the end of September through April. Annuals can be installed from late September to February. Some gardeners prefer to wait until October, as cooler temperatures also help kill off whitefly populations which can quickly decimate plants.
The warm season starts with planting in mid to late February. Some plants will make it through the summer's heat; others will end their growth when the heat arrives in May or June.
A rule of thumb for cool-season vegetables is that we eat parts of the plant itself, such as leaves (lettuces/greens), stems (kale, broccoli and other cole crops) and roots (beets, carrots, turnips, onions). In the warm season, we eat the seeds and fruits (tomatoes, peppers, cukes). The major exception is peas. Although we eat the seeds, we plant them in the cool season.
Lots of flowers can be planted for enjoyment from late September through April. Some of my favorite easy-to-grow annuals include calendula, bachelor's button, pansies and violas, nasturiums, stock, snapdragons, alyssum, dusty miller, poppies and dianthus to name a few. Wildflowers are also seeded in the fall for spring bloom. October is a good month for that.
Warm-season annuals include sunflowers, tithonia, zinnia, coreposis, cosmos, gaillardia, black-eyed Susan, coneflower, lisianthus, and vinca. Low-water-use desert-adapted perennials are another good source of color, such as desert marigold, chocolate flower, angelita daisy and others.
Contact the Phoenix City Water Conservation Department for a free copy of Landscape Plants for the Arizona Desert. It is a color guide listing more than 200 low-water-use plants, including annual and perennial flowers.
A good reference book for sale that contains planting calendars for the low desert is called "Desert Gardening for Beginners: How to Grow Vegetables, Flowers and Herbs in an Arid Climate." It is written by local Master Gardeners. ISBN 0-9651987-2-3. Good luck!
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