Improve Garden Soil
Garden beds with flowers and vegetables need nutrient-rich, organic soil. Desert soils contain scant organic matter (less than one-half of one percent) so it is important to incorporate it before each planting season. Layer 4 to 6 inches of compost on top of beds. Add a nitrogen and phosphorus fertilizer at the same time, and dig it in to a depth of 12 to 18 inches. There is usually plenty of potassium in desert soils so it doesn't need to be added. If time permits before planting, water the soil and let weed seeds sprout so you can remove them.
Fertilize Deciduous Fruit Trees
Apply nitrogen to deciduous fruit trees, such as apple, apricot, peach, and plum trees, as temperatures warm and new growth begins leafing out. Wait until the last frost date passes because tender new growth is easily damaged if temperatures dip unexpectedly. March 15 is an average last frost date in the low desert, but it can vary depending on elevation changes and microclimates. Not sure what your frost date is? Check with your county cooperative extension office.
Plant Tomatoes and Peppers
Set out tomato and pepper transplants after the last frost date in your area. Mix nitrogen and phosphorus into the bottom of the planting hole. Last frost dates vary considerably even within a short distance, so it's a good idea to protect these tender vegetables for an extra week or two, just in case there is a late frost. Enclose in chicken wire (or tomato cages) and wrap burlap around them.
Most navel and sweet oranges should be harvested by now as their season comes to an end. Valencia oranges and grapefruit are still viable and sweet on the tree. Mature citrus trees can produce enormous quantities of fruit. If you can't eat it all, organize your friends and neighbors to have a gleaning party. Donate the excess to a food bank.
Winter rains have produced an abundant and healthy crop of annual weeds. Yank those interlopers quickly before they use up soil nutrients and moisture, and don't let them go to seed. Seeds can lie in wait for years in the soil, and germinate when conditions are to their liking (like this year's heavy rain). Their green foliage is a good source of nitrogen for the compost pile, but only if seed-free.