On Oct. 14 from 9 a.m. until noon, the Center for Urban Water Conservation in North Las Vegas (where the University Orchard is located) will host an educational event for homeowners and HOA members who want to save water on their landscapes. Educational presentations will focus on our water shortage, search for beautiful desert plants for low-water-use landscapes and where to plant them. Desert natives and seeds grown at the center or found at local nurseries will be available for purchase.
This event is free to the public. Sign up through Eventbrite at https://www.eventbrite.com/e/722428331587?
Speaker sessions will cover summer pruning, 9 a.m.; honeybees, 9:30; palms, 10; edible landscapes, 10:30; native plants and landscapes, 11; and grapes, 11:30.
Q: Caterpillars are on most of the plants in our neighborhood. Do you know what it is and what we can use to get rid of them?
A: A caterpillar explosion has occurred all through Las Vegas and Arizona where it’s been raining, and because of the water, food supply is abundant. Caterpillars can be a common sight where there are summer monsoons and rains such as those in central and southern Arizona and this year as far north as Las Vegas. Southern Arizona (Sonoran Desert) gets more than double the water than the Mojave Desert so there is a lot more food to sustain caterpillars.
They should be easy to control with soap and water sprays, Neem oil and any commercial pesticide available such as Sevin. It’s important to follow any label directions for the right dosage when you spray these immature insects. After they die from any kind of pesticide, then there’s always the cleanup.
However, this year’s hatch has been particularly large compared with previous years. The conditions must be perfect; several large rains following each other that cause plants to grow and provide food and coverage. Sometimes this food might be our vegetables, landscape plants and fruit trees. Sometimes this food is found only in the desert.
These caterpillars are typically the white-lined sphinx moth (hummingbird moth) painted in a lime green or yellow with black longitudinal stripes, with or without a spine on the end. These insects sometimes act as pollinators just like butterflies, flies and other flower-loving insects.
After they have gained the right size, they drop to the ground and develop into the sphinx moth in moist soil. On the negative side, we might see a burst of pest problems in our tomatoes and grapes due to their munching. So be prepared.
Q: Should I leave the pine needles around the basin of their trees, or should I rake them out and pick them up? I feel that cleaning them from under the trees helps the water penetrate into the soil quicker and not sit atop the needles. My part-time gardener says I should keep them around the trees so that they act as a mulch. Who is correct?
A: Your gardener is correct, but in a reverse sense, you are, too. If you can stand leaving the pine needles in place, they will decompose (provided the soil is kept moist) more slowly than fine woodchips. But they will decompose.
These decomposing pine needles add to the soil’s nutrition and soil’s organic content. If there are enough of them (2-3 inches deep), they conserve soil moisture, add organics to the soil as they rot, keep the soil cooler and help prevent annual weeds.
Rake the pine needles so they are 2-3 inches deep under at least half of the canopy of the pine tree. If the trees are not yet 10 years old (or bark has not started to develop on the trunk), then keep them away from the trunk 6 to 12 inches (keep that soil uncovered and dry).
Q: Have you ever seen a sago palm that has different types of leaves and fronds? I can’t find any pictures of a sago that look like mine. Also, mine grew extremely fast — in a matter of weeks. I purchased the sago with the original fronds that are dark colored. The tree had been living about 6 feet from a windmill palm tree. Do you think it could have crossed?
A: There are different types or species and even genera of sago palms. These are based on their appearance, how big they grow and where they are available. Most are classified as the king sago palm, queen sago, queen sago palm and (a totally different genus and species) and the true sago palm, to name just a few.
The king sago palm, or Cycas revoluta, is the most widely grown type and most commonly available. The king sago palm is quite small, growing only to about 8 feet tall and 8 feet wide, making it small enough to qualify as an indoor plant.
Sago palms come from a variety of climates but mostly tropical or semitropical. There are a lot of different kinds to pick from if you can search online or buy them from out-of-the-way places.
I occasionally look at Lowe’s and Home Depot’s garden centers for occasional deals, but you have to know what you’re buying or at least be willing to take a loss if you don’t.
Rare sago palms can also be purchased from nurseries online as well as eBay.
All the information is the same regarding the fast-growing sago palms. They prefer to grow on the east side away from direct sunlight or at least in what we call “filtered light” or speckled light. They also prefer growing in amended soils and not in rock mulch.
Be careful of fast-growing sago palms or cycads. It usually means they become larger than most others. Most sago palms are characterized as slow growers.
Q: I just purchased a dwarf fig tree (Little Miss Figgy) at the fall plant sale at the Springs Preserve. I was planning to put it in a planter on the north side of my house. In the summer, it gets full sun but now is getting a lot of shade. Is that a deal breaker for the fig?
A: It should be fine with that amount of light on the north side of a home. All fruit trees require at least six — and prefer to get a minimum of eight — hours of sunlight every day when in production. That includes fig trees.
It is a small tree (suitable for container production, 6 feet tall by 4 feet wide) and develops dark purple fruit with red pulp. It was a chance mutation of Violette de Bordeaux’ fig from South Carolina.
I have not grown that variety, but all varieties of figs seem to do well in our climate. At that size, a 15-gallon nursery container should be adequate.
Most people growing fig trees in the ground don’t water them often enough when they start into their second batch of fruit. Because it’s smaller, it should use less water (but not watered less often) when planted in the ground.
Q: I have some cactuses in my backyard. Should I fertilize them and when?
A: The standard answer is to fertilize them lightly in the spring of each year. That is the standard answer.
The purpose of fertilizer is to give the plants what they need or what is lacking in the soil. Once plants have what they need, stand back and give them a chance to grow. Giving more fertilizer than they need and watering plants more often does not necessarily make them grow faster.
Fertilizers are not a magic “on and off” switch; you can’t force plants to get larger and bigger by giving them more fertilizer than what they need. All plants have a genetic maximum at which they can grow. That is why most cactuses grow slowly, and other plants may or may not, depending on their genetics. For cactuses, it depends on the fertilizer level, watering and soil mix.
There is one fertilizer exception and it is a bit tricky. Nitrogen fertilizers increase the speed at which any plant, including cactuses, gets larger but you must be careful. There is a danger from growing too fast for all plants. The fancy term is “luxury consumption.”
To maximize growth, apply nitrogen fertilizers no more than twice during their growing season. Be judicious when watering them and don’t let the soil stay wet. But if your cactuses are growing well without it, then don’t use it.
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.