The young prickly pear pads are edible. They are high in nutrients such as vitamin A, vitamin C and calcium, so you'll get the added benefit of balanced or reduced blood-sugar levels. Prepare and cook them like most vegetables. The large red or purple fruits are delicious and sweet. Remove the spines and skin them carefully -- they are indeed prickly -- then slice and eat.
Ironwood flowers are edible raw, as are the seeds -- but the seeds are better if boiled or blanched and can be eaten much like edamame or green soy beans. The seeds can also be sprouted by soaking for 10 to 12 hours, then rinsing every day until they split open. Cook lightly and add salt if permitted in your diet. Dried seeds can be warmed or heated in a skillet. They pop as they cook.
Mesquite is quite versatile. You can make syrups or mill the flour to use in different recipes. Use this high-protein food for tortillas or bake it into cornbread, crackers and dozens of sweet treats. Adding mesquite meal to other foods helps reduce the glycemic index, too, so you'll have reduced carbohydrates as a benefit. A form of tea can also be made from the meal, while jelly can be made from the pods.
Many other desert plants provide nourishment. Research which parts to use, such as leaves, stems, flowers, buds, roots and tubers. Items to check out include jojoba, wild onions, panic grass, palms such as the date palm, agave and desert amaranth. Studying them will prepare you for a wilderness survival episode, but use caution when choosing any plant you do not recognize or haven't eaten before.