Improve Soil in Garden Beds
To get the garden ready for fall crops, add organic matter, digging a 4- to 6-inch layer of compost into the soil to a depth of 12 to 18 inches, add fertilizer containing nitrogen and phosphorous (desert soils have plenty of potassium), and add soil sulfur (3 pounds per 100 square feet) to enhance drainage and reduce alkalinity.
Plant Cacti and Succulents
Propagate jointed cacti such as prickly pears and chollas by cutting them with a clean, sharp knife at the joint. Separate aloe and agave "pups" from their parents, retaining as much root as possible. Allow the open cuts to callus for a week before transplanting into well-drained soil. Their roots will rot if kept too wet.
Fall Plant Selection
Late September and October are prime planting months in the desert. Decide what types of plants you want in your landscape, what cultural requirements they have, and what conditions your landscape provides. Look through plant books and Web sites for growing information and prepare a list of possibilities. This will help prevent \"impulse buys\" of plants not suited to your needs.
As fall temperatures begin to decline, watering can be cut back. Monitor your plants' water needs and continue to look for signs of stress, such as wilting, wrinkling, or yellowing leaves. Adjust the timer on automatic irrigation systems accordingly and continue to water slowly and deeply to soak the entire root zone, regardless of temperatures.
In high-elevations areas you can start planting spring-blooming bulbs now until about mid-October. Plant in a rich soil and add a phosphorous source such as Bulb Booster to the bottom of the planting hole. If rodents are a problem, encase bulbs in wire mesh baskets. People in low elevations should chill tulip and hyacinth bulbs for about 6 weeks before planting. Other spring-blooming bulbs, such as daffodils, don't require pre-chilling.