Answer: There are two distinct growing seasons in the low desert with different annuals 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 good reference book 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." ISBN 0-9651987-2-3. You can also download the Flower Planting Guide for the Low Desert from the University of Arizona Cooperative Extension publication website. http://ag.arizona.edu/pubs/
Here are the best planting periods for the flowers you asked about.
Hollyhocks Sept-Oct, and Feb-March.
Sweet peas Oct-Feb
Q&A Library Searching Tips