Why Desert Soils Kill Plants

Q. I really didn’t understand the “soil” here, did not dig large enough holes and didn’t amend the dirt when I planted my oleanders. It’s been 5 years and I’ve tried to correct their scrawny growth by adding plenty of mulch and fertilizing regularly but the growth continues to be weak.  Any suggestions how to encourage stronger growth?

Its like backpedaling when you try to amend the soil after planting. Do it at the beginning and save yourself some grief and hard work.

A. As a friend of mine would say, “Pay me now or pay me later.” At some point you will pay the price for good plant growth and modify the soil at planting time or later when it is more difficult.

Amend Soil at Planting Time

            Whether it is raw desert soil or imported “soil” brought into the development by the developer, soils in developments are typically horrible in the Las Vegas valley. Constructing planting holes at the very beginning and using amendments are extremely important for good plant growth. Its cheap insurance.

Look at the size hole this guy dug for a 5 gallon mesquite tree. The brownish soil tells me it probably has 2% organic matter already but this mesquite tree will LOVE it. Just remember to mix the amended soil with native soil at the perimeter so there is no "hard edge" for roots to grow through.

Oleanders like Wet Winters and Hot Dry Summers

            Oleanders are Mediterranean plants. They grow well in a Mediterranean climate and soils but need some help when grown in the desert. The help is in the form of constructing a decent planting hole, using soil amendments that encourage good growth when the plant is young, and adding supplemental water. They love the heat and low humidity of our desert environment.

Oleander is tough. If given enough water they can survive just about anywhere.

            Now you have the job of amending the soil after it has been planted. Hopefully, your oleanders were planted with at least six hours of full sun every day. If not, prune any interfering trees so that they receive enough sunlight.

Fixing Trees After Planting

            Auger holes 12 inches deep around these plants so the holes occupy about half of the surface area. Fill these holes with a rich compost or make a rich compost by mixing a granular fertilizer like 16-16-16 with standard compost at the rate of two Grande coffee cups full for each cubic foot of compost.

            Construct a donut around the plant for containing the irrigation water and hand irrigate for about two weeks filling the donut each time. After that, let your irrigation system take over. Prune it after about three to four years of growth and fertilize lightly each spring.