Improve Garden Soil
If you have not yet done so, layer 4 to 6 inches of compost or well-aged manure on top of vegetable and flower beds and dig in to a depth of 12 to 18 inches. This addition is essential before each planting season (fall and spring) because desert soils contain very little organic matter, and what there is disappears quickly. Organic matter improves drainage in clay soil, holds moisture in sandy soil, and adds nutrients as it decomposes to all soil types. Over time, improving soil with organic matter will create a rich, dark, workable soil that's home to an army of earthworms, who will continue the soil-building process for you.
Sow seeds for cool-season veggies including beets, bok choy, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, chard, lettuces and salad greens, kale, kohlrabi, green onions, peas, radishes, and turnips.
Add Trees and other Landscape Plants
Fall is perfect weather for transplanting native and desert-adapted trees, shrubs, ground covers, vines, perennials, ornamental grasses, cacti, and succulents. Any tropical or cold-tender plants should be planted early so they can establish before potential early freezes.
Sow seeds or transplants for borage, chamomile, chervil, chives, cilantro, dill, fennel, horehound, lemon balm, parsley, salad burnet, and French sorrel. Lavender, lemongrass, lemon verbena, oregano, mint, sage, santolina, and thyme are easier to get growing from transplants.
If agaves have rotted and collapsed, that's a sign that agave weevils have done their worst. Dig up what's left of the plant and root system and discard it in the trash. If agaves have bloomed, leave the towering flower stalk to dry in place as a perch for birds.