Transplant Warm-Season Vegetables
To get a jumpstart on the season, tomato, pepper and eggplant can be transplanted now, but they must be protected from possible frost. Plant where they receive 6 to 8 hours of full sun daily. Incorporate plenty of compost in the soil, and mix a source of phosphorus into the bottom of the planting hole. Phosphorus promotes flowering and fruiting. Water well immediately and keep soil moist, but not wet, until the root system establishes.
If you didn't feed citrus trees in January, now's the time to provide one-third of their total annual nitrogen requirement. Fertilize should be applied at the edges of the tree's canopy or dripline where feeder roots are actively growing. The amount to apply varies depending on the tree's size and how long it's been planted. A mature tree requires about 1 1/2 pounds of actual nitrogen per year, so apply 1/3 of that, about 1/2 pound of nitrogen.
Protect From Late Freezes
Monitor the weather forecasts and protect annuals and frost-tender tropicals such as citrus, bougainvillea, hibiscus, natal plum and lantana. Cover plants at sunset with frost cloth, burlap, or old sheets. Remove the protection in the morning before 10 am, so it doesn't heat up too much underneath.
Roses start their major bloom cycle in the low desert in April. Fertilize bushes now to help prepare them. Use a fertilizer formulated for roses or an organic fertilizer that contains nitrogen and phosphorus. Most desert soils have sufficient potassium. Add one-quarter cup of epsom salts (magnesium sulfate) per bush to help prevent magnesium deficiency. Water soil well before and after applying fertilizers to prevent root burn.
Recent rains have promoted a quick flush of green weeds. Pull them as soon as they appear so they don't compete with your plants for nutrients and water. Never let weeds go to seed. One of the reasons weeds are so successful is they produce a few zillion seeds per plant. Weed plants are a good source of nitrogen for the compost pile as long as they haven't gone to seed. You can also let them lay on top of the soil after pulling, as they will decompose and release their nutrients over time.