Eight-week class to offer landscaping tips

A: I have a weekly class on designing your own home landscape starting July 7 for eight weeks on Saturday morning. The class size is limited. If you do the homework I lay out, in eight weeks you will have a finished landscape design that you can be proud of and totally functional for our desert climate.

Sign up for this class on Eventbrite by Googling the words “Eventbrite” and “Landscape Design With the Desert in Mind.”

Expect to pay somewhere between $3 and $10 per square foot to have someone install a finished landscape. These creations will be “decorations” around your house and do not create much usable space outside.

My design class shows you how to create usable living spaces, based on your needs and wants, outside of your home. Essentially this outside space becomes part of your functional living area and increases livable square footage of your home.

I promote the mini-oasis landscape design concept where water is used to enhance outside living spaces and reduce air conditioner power consumption.

Q: My 4-year-old Thompson seedless grapevine has scarring on the fruit and white spots on the leaves. What causes this, and how do I prevent it?

A: The scarring on the fruit is caused by very tiny insects called western flower thrips. If their populations are heavy, they also may attack new grape shoots as they are growing. Later they can attack the berries in the grape clusters, causing them to scar.

These insects begin feeding on the petals of flowers as soon as they open, as well as the ovary inside the flower. When the fruits begin to form, they attack the tender skin of hairless grape berries. Repeat feeding of these insects on fruit causes scarring as the fruit surface heals and the berries get larger.

I have not seen this insect reported before on grapes growing in Southern Nevada, but they are somewhat common in California vineyards growing Thompson seedless, perlette, red globe, Italia and other dessert grapes. It doesn’t seem to be as much of a problem on wine grapes.

I think this insect was a problem primarily because of our cool, wet spring this year. I don’t think it will be much of a problem in years to come if spring weather is warm and dry. But watch for it in future years if the spring is cool and wet.

This same insect attacks the petals of rose flowers, causing the flowers to open poorly and look shabby. We can see the same type of fruit scarring on nectarines. In extreme cases, nectarine fruits are unusable.

Western flower thrips are not easy to control, but a spray that has been effective with repeat applications is Spinosad. Be sure to read the label directions. Alternate this spray with Neem Oil or soap sprays. Avoid spraying flowers with anything when they are open and if honeybees are in the area.

The nice thing about using Spinosad on grapes is it can control three different insect problems with repeat applications starting at the end of March or early April: western flower thrips, leaf hoppers and skeletonizers.

Q: Female African sumac trees are a pain in the neck. They produce seed that goes everywhere and sprouts up all over the landscape. I would prefer male trees. How can you tell the difference at the nursery?

A: Gender is very complicated in the plant world. With trees that have male and female flowers on separate trees, asexual propagation such as grafting or budding is frequently used to produce new trees. Knowing the gender of a tree, if it has one, can be important if you want a tree that does or doesn’t produce seed or fruit.

Asexual propagation takes plant parts such as buds, stems, leaves or roots from a desirable tree and basically clones a new tree. The tree resulting from asexual propagation is identical to its parent. If the parent was a male tree, it will be male. If the parent was female, it will be female.

Trees like fruitless mulberry and seedless ash are produced by asexual propagation.

If a tree is grown from seed (sexual propagation), the new tree has a 50/50 chance of being male or female. We don’t know which gender it will be until it produces flowers or seed. Some trees take several years before they are old enough to produce flowers.

African sumac is grown from seed. Most people don’t know or care when they buy it if an African sumac tree is male or female. Several years later, when it begins flowering and producing seed and suckers, they might care, but at the time of purchase, it isn’t important. It’s an African sumac.

When selecting African sumac, if you want a male tree, try looking for a lack of suckers at the base of the tree. Male African sumac trees typically produce fewer suckers than female trees.

Also look for seedlings that might be sprouting from the soil surrounding the tree. If the tree has been flowering, seedlings are produced by female trees only.

Q: I’m an avid gardener from Colorado. I had a large vegetable garden there with pretty good success. This spring I built a raised bed and planted a variety of vegetables from starters. They are really struggling. They get plenty of water and have been fed regularly.

A: The keys to successful vegetable gardening here is starting with a decent soil, installing a good irrigation system, not hand watering and planting at the right time of year. I don’t need to tell you it’s important to visit that vegetable garden every day. It’s not a grocery store.

As you already know, this is not Colorado. Colorado is a dry, arid state but nothing like the Mojave Desert. I feel bad for people moving here from San Francisco, Seattle or Portland and gardening here for the first time.

Starting with a decent soil is critical. I have amended Mojave Desert soil with compost and had no problems growing vegetables in it. However, there are some very bad soils in the Las Vegas Valley. If you have this kind of soil, then your only alternative is to install raised beds and fill these beds with a good soil mix.

What most gardeners forget to do is add compost to the garden soil every year before planting. Not much compost is needed, but about a 1-inch layer on top of the soil and mixed into the top 8 inches is enough to keep vegetables growing strong.

Irrigation is a must, and drip irrigation is the only way to go. The installed drip irrigation should be a closed loop design with one location to flush the lines once a month.

I prefer ½-inch drip tubing with embedded emitters 12 inches apart and drip lines 12 inches apart. The drip irrigation system should have a pressure regulator and screen filter feeding water to the drip emitters.

Correct timing for planting is essential. The bible for vegetable gardening is Dr. Sylvan Witwer’s publication, “Vegetable Gardening in Moapa and Virgin Valleys,” available from the Nevada Cooperative Extension. He was the vegetable specialist for Michigan State University before retiring and growing vegetables in Overton, Nevada, for eight years. It is a free online publication available from UNR Cooperative Extension.

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.