We are smack dab in the middle of the best planting time of the year right now. Select small trees for one-story homes (up to about 25 feet mature height) and medium-sized trees (up to about 35 feet) for two-story homes. Shade the south and west walls and windows of a home to reduce the cost of summer cooling.
Plant trees at least 6 to 8 feet from these walls and keep applied irrigation water 3 feet from the foundation. Do not plant large trees (above 40 feet when mature) in all but the largest residential landscapes.
Most lawns are planted now either by seed or sod. The most popular lawn grasses in our climate zone are the turf-type tall fescues that are used locally for sod.
When buying seed, stay away from pasture-type lawn grass seed unless you intend it for an athletic field. It’s hardy but rough to the touch. You’ll need about 12 to 15 pounds of turfgrass-type grass seed for every 1,000 square feet of lawn area you intend to plant.
This type of lawn grass is mowed at the highest setting of the lawnmower — 3 inches. Tall fescue is oftentimes mowed too short here, which encourages summer heat damage and invasion by Bermuda grass.
It is extremely important the irrigation system is designed and installed to throw its water evenly to the neighboring irrigation heads to survive the high temperatures next summer. If the water pressure is too high, you might need to install a pressure regulator. Consider installing a pressure vacuum breaker if you don’t have one.
It’s still too early for major pruning of landscape and fruit trees. Look for pruning classes starting around mid-December.
Q: I have a 10-year-old black or Idaho locust that I planted. It was planted in amended soil and gets plenty of water. It is now about 20 feet tall, and this year the leaves only grew on one side and I am afraid it will die. One half the tree has no leaves.
A: Locust trees, whether Idaho or black locust, struggle in the heat of the desert for two reasons. First, they have trouble handling strong desert heat and sun, and second, they have thin outer bark on younger parts of the tree until these parts get older. This sunburn damage is followed by insect borer attacks, which usually kill the tree.
Plant locust trees on the east or north side of the home and out of late afternoon heat and direct sunlight. Never plant them in areas surrounded by rock mulch.
Locust trees are mesic plants, originating from moist climates. Mesic plants struggle in rock mulch, aka desert landscaping. These types of plants prefer good compost mixed in the soil at planting time, the soil moist surrounding the tree and covered with 4 inches of wood chips.
Because of their thin outer bark, locust trees do not like extensive pruning in desert climates, ever. A recipe for killing a locust tree here is planting it on the south or west side of the home and pruning limbs and branches so the trunk and large limbs receive intense desert sunlight. Intense sunburn kills parts of the tree exposed to the intense sun, oftentimes the first summer after it’s pruned.
Once the tree gets hit with sunburn, wood-boring insects attack these damaged areas in their attempt to finish it off. It might take two, three or four years, but they will kill it.
What to do? If the tree is worth saving, then enrich soil under the tree canopy with compost. If rock is present, rake it back 6 feet or more and spread an inch layer of compost on the surface of the soil, lightly dig it in and water it.
Cover this area with a 4-inch layer of wood chips, not rock. If you think the tree has borers, apply a systemic soiled trench of an insecticide following the label.
Q: I planted two 36-inch boxed African sumacs last week. How much water should I give them and how often should I water them?
A: You forgot the third question: Over what area should the water be applied? The applied water should wet all the soil inside the box as well as soil extending 18 inches beyond the box. Enough water should be applied each time it’s irrigated to wet the soil 18 inches deep. It should be watered again when half of the volume of water you applied is gone.
Before I forget, if the tree wasn’t watered thoroughly when it was planted I would water all of the soil in this area thoroughly with a hose attached to a sprinkler for about one hour. The next day I would do it again. Just twice to settle the soil around the rootball.
Water needs to be applied to the soil inside the box and outside the box. After the irrigation is finished, use a 4-foot length of skinny rebar pushed in the soil in several spots to make sure the water reached 18 inches deep.
Buy a house plant moisture meter and stick it in the amended soil in three or four locations about 4 inches deep and apply the next watering when the meter averages “five” on the meter. Repeat this about four times a year when there is a major change in the seasons.
As trees and shrubs get larger, more area under the plant needs water so the irrigated area is larger.
Q: My new home has a dead lawn in the backyard. I was considering hybrid Bermuda grass like TifTuf Bermuda since it handles the heat better. What’s your opinion?
A: I won’t tell you what to do, but I will give you the pluses and minuses. All the Bermuda grasses are warm-season grasses, which means they like the heat but turn brown for three or four months during our winter. The traditional grass grown in most lawns in our desert is turf-type tall fescue which is a cool-season grass. Cool-season grasses such as the fescues, rye and bluegrasses like the cooler months of the year but struggle during the heat of summer.
Warm-season grasses like TifTuf hybrid Bermuda use about 20 percent less water than most traditional lawns. They are prettier to look at and softer to the touch. They don’t have the disease problems that fescue has in the summer. They repair themselves during the summer when damaged by dogs.
Now the negatives. Warm-season grasses are usually prettier to look at but are more costly to maintain. They turn brown from around mid- or late November through about March. This means if you want a green winter lawn, you must overseed it with a cool-season grass for the winter months.
Most warm-season grasses require a special mower for cutting it, and these are more expensive to maintain. Maintenance costs are higher because of overseeding in the fall, periodic power raking and aerating, and more frequent applications of fertilizer to make it look good. The biggest reason why most residents of Las Vegas do not want a warm-season lawn is that it turns brown in the winter.
I thought warm-season grasses would be more popular in Las Vegas than they are because of the cost of water, but I was wrong. Most people prefer to have a green lawn during the winter that doesn’t require much effort.
Q: What varieties of figs do you recommend for the best grown in the desert? Do you have to provide cold protection? Which varieties have the lowest water requirements?
A: I have tried many kinds of figs over the years here and never had problems except with Brown Turkey. But that could have been my fault. I have grown yellow figs (white), purple, black, striped and brown types. All of them successfully produced fruit if they are given enough water.
They can be successfully grown with winter temperatures down to about 15 degrees without any damage. The most common reasons for failure are not giving them enough water during the summer months and poor soil preparation at the time of planting.
I prefer to cover the soil with 4 inches of wood chips and deliver about 30 gallons of water at each irrigation. They can handle full sun with no problems provided they are given enough water at each irrigation. Apply that water to at least half the area under its canopy or about a 6-foot-diameter basin. They are one of the few fruit trees that can be cut nearly to the ground and still produce fruit the next year.
Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.