Both warm-, cool-season grasses grow in Las Vegas

My class on creating a desert orchard will be held in November for four Saturday afternoon sessions. It begins Nov. 3. You can sign up for it on Eventbrite or contact me and I can arrange it for you.

Q: Are there other lawn grasses beside tall fescue and Bermuda grass that will grow here?

A: Many different lawn grasses will grow in Las Vegas, but the problems are availability and which cultivars or varieties to use. Most people want what’s available currently in the Las Vegas markets because they are in a hurry and that narrows your selection to mostly tall fescue, sometimes called “fescue” by some.

Las Vegas sits in, using landscape lingo, the “intermediate” zone for growing lawn grasses. There are three identified zones in the United States for lawn grasses: cool season in the Northern states, warm season in the Southern states and the intermediate zone.

We sit in the intermediate zone, which means we can grow both cool season and warm season grasses. That can be an advantage, it can also be a problem. Our climate is not clearly cool season and not clearly warm season, and so we have problems with both.

The major delimiting factor is winter low temperatures that can kill some lawn grasses.

The warm season grasses include all the different varieties of Bermuda grass but also zoysia, St. Augustine, buffalo, centipede and others. The cool season grasses include tall fescues but also Kentucky bluegrasses and perennial ryegrass. All warm and cool season grasses grow here, but heat tolerance is very important with bluegrass and ryegrass lawns because of our high summer temperatures.

Cool season lawns stay green 12 months of the year here. Warm season lawns turn brown during the late fall and winter months. Some can handle overseeding in the fall with ryegrass if a green lawn is wanted through the winter, but some do not.

The predominant lawns in Las Vegas during the 1980s and earlier were Kentucky bluegrass for high-end lawns and common Bermuda grass for low-end lawns. Heat tolerant perennial ryegrass started making appearances in the late 1980s. Annual ryegrass was used for overseeding common Bermuda during the winter while managed back to common Bermuda in midspring.

The variety of a plant chosen, whether it’s a lawn grass or a vegetable, can be just as important as the kind selected. This is an important concept to learn.

Q: I bought an Anacacho orchid tree at the Springs Preserve plant sale. Everyone tells me it needs rapidly drained soil, so I will use cactus soil. Should I put a couple inches of compost on top to enrich it?

A: That’s an interesting plant you bought. It’s not used much in the Las Vegas area because it’s not available, but it is a bit more popular in Arizona and Texas. Native to the Chihuahuan Desert, it’s a good choice for a desert landscape here.

It’s a small tree, roundish up to about 12 feet but can get 20 feet tall if well-managed and planted in rich, moist soils.

Drainage is correct. The soil must have good drainage so with no drainage problems in your soils it should be fine. Avoid layering soil as this impedes drainage. A cactus soil is not necessary, but amended soil throughout the planting hole will provide enough good drainage.

Mix maybe 20 percent compost with the soil used for backfilling around the roots or use a ready-made soil mix. It is native to the Chihuahuan Desert which has more organics in the soil than soils in the Mojave Desert.

Compost amendments improve drainage through the soil. Rich compost provides fertilizer. With a rich compost, no need to fertilize for about two years.

Make sure the soil at the bottom of the planting hole drains water. That’s important. The hole should drain water overnight or sooner after filling it. If not, plant it on a mound.

Avoid extremely hot locations in the landscape such as south-facing exposures near hot, radiating walls. The southern exposure is OK, but don’t put it close to a hot wall.

This plant grows in desert canyons in the wild. What does that tell you? It needs deep watering, open spaces surrounded by desert soils and rock and possible protection from late afternoon sun.

Most cold winters, it should be deciduous in Las Vegas, unlike places with warmer winters. It’s not terribly pretty during the winter months, but it should give you good floral displays if pruned during the winter.

Q: Our water bill gets high in the summertime. I suspect we’re overwatering but don’t know for sure. What strategy can we go through to determine when plants are getting just enough water? More than enough is hard to determine.

A: This requires a small investment on your part in the beginning. The two questions that need answering are when to water and how long (minutes) to water. You will need some sort of moisture meter that measures soil moisture and a steel rod for determining how long to water.

There are two types of soil moisture meters available. One is inexpensive, and you can buy it at box stores for houseplants for less than $10. A better one can be bought online for $40 to $75, can be pushed into more difficult soil and lasts longer. Manufacturers are Reotemp and Lincoln.

All of them have the same scale for moisture readings, 1 to 10. After calibration, recently watered soil will read 10 on this scale. Irrigate days later when the scale reads six. The expensive one lasts longer and can be used in more difficult soils, but it gives you about the same reading as the inexpensive one.

How much water to apply or how many minutes on an irrigation controller requires a steel rod about 3 feet long. Use a 3/8-inch diameter steel rebar that is 3 feet long. They can be purchased at the major box stores for about $1. Shortly after the irrigation, push the steel rod into the wet soil in several spots.

Steel bars slide easily through wet soil until they hit dry soil. Trees and large shrubs should have wet soil down to at least 24 inches. Twelve inches is usually enough for most other plants, including lawns and vegetables.

Water long enough, or apply enough gallons, to make the soil wet to the desired depth for all the plants on that circuit or valve. If some plants aren’t getting enough water while others are, add more emitters to those that aren’t.

The first two seasons you might have to measure soil moisture and use the steel bar five or six times to get a “feel” for when to water. But after the second year you will start recognizing a seasonal pattern to irrigating plants in your landscape and you will not need them as often.

Q: I have oleanders in my backyard and noticed some yellow bugs on the flower stems. What are they and how do I get rid of them?

A: These are highly specialized yellow aphids simply called “oleander aphids” because they have adapted to feed on the toxic plant juices of this plant. They might be poisonous themselves because they drink so much of the oleander fluids.

Aphids can be red in color, green, brown, black and, in your case, yellow. Some aphids are general feeders like the green peach aphid and can be found sucking plant juices on a variety of plants while most are very specific, like yours, only feeding on oleander.

Control is the same for all aphids. The products with the least impact on human health are soaps and oils like Safer’s Insecticidal Soap and Neem Oil.

Other more potent and specific chemical controls are the general garden insecticides like pyrethrin products. These products last longer after you spray so they give long lasting control while the soaps and oils must be sprayed more often and only when the problem occurs.

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.