Amend the soil in the planting area so that it is well-drained, if necessary. Add 3 to 4 inches of coarse sand or grit and use a gardening fork to combine it with the top 6 inches of soil. Lavender thrives in sandy or gritty soil.
Top-dress the soil around the lavender plant with mulch. Compost is the ideal mulch material for the desert-grown lavender since it supplies nutrients while keeping the soil cool. Spread the compost on the soil completely around the plant and out to its widest point; you will not need supplemental fertilizer.
Stick your finger into the soil to determine the moisture content. Water the lavender when the soil is completely dry. Saturate the soil and then allow it to dry again before you water. If the lavender is planted in all-day sun, keep an eye on the soil as it may dry out quicker during the hottest part of the summer in the desert.
Cut off all the flower heads when they die back. In the spring, cut off 1 inch from the tip of each stem. Do not prune the lavender at all after September as it may promote new growth which can be killed in an early frost.
Protect the lavender from high winds in the winter by mounding mulch over the plant or erecting a shelter around it with burlap attached to wooden posts.