Drawback to Woodchips: They do attract vermin

Q. My backyard has several planting beds containing roses, rosemary, mock orange, euonymus, pyracantha, lantana, sago palms, and other plants. I added rock to the soil surface eight years ago and these plants started to decline in about five years. I decided to remove the rock and put woodchips down instead but afraid of roaches entering the house from the woodchips.

Irrigation valve box amongst plants receiving water. When you combine woodchips, water and a valve box it is normal for cockroaches and spiders to live and enter there. Spray the inside of these boxes with an insecticide once a year to help reduce these numbers. But this will not stop them from helping to decompose the woodhips.

A. Insects such as cockroaches like water and something to eat. They live in the woodchips exposed to water because they help break down debris from the wood chips. Cockroaches, unpleasant as they are, are decomposers. Their favorite place to congregate in the landscape is in irrigation boxes where it stays wet. They are attracted to these wet areas and warmth of your home when it gets cold so they may come inside as their populations get larger.

Keep landscape areas close to the home dry. Apply water to landscape plants no closer than 3 feet from your house exterior walls. There isn’t a good reason to apply water closer than this. In a desert climate where there is limited rainfall, plant roots follow irrigation water. Irrigating foundation plants on the side away from the home causes their roots to grow in that direction. Keeping the soil dry surrounding your home also reduces water damage to the cement as well as reducing insect problems inside the home.

After removing the rock and before you apply woodchips, sprinkle the wet areas around plants with a rich compost to help feed the plants, enrich the soil, and start the decomposition process.

Pittman Area of Las Vegas and Managing its Soil

Q. I am a young gardener (25) in Henderson, specifically Green Valley, near the Pittman Wash. I am interested in the cultivation of plants not only for their aesthetic value, but their benefit to wildlife as well. This has steered my interests to pedology and edaphology as well as horticulture and botany.

From what I have gathered from the USDA soil survey of the Las Vegas Valley (published in 1985), my residence (and therefore garden) lies near a boundary between the ‘McCarran’ and ‘Jean-arizo’ soil series. 

From direct observation, it seems I am situated more so in the McCarran series area. With massive soil in the lower C horizon, and sticky and plastic qualities throughout, how does this effect irrigation protocols and amendments types and amounts? The reason I ask is I recently purchased some premium compost from Viragrow (thanks for the rec), and want to make sure I use the correct ratio of compost to native soil to prevent reinforcing any drainage issues associated with clay soils. The bare, native soil I am about to cultivate drains moderately slowly (some areas 15 minutes, other areas up to an hour). The only plants that have ever been in there were some poorly pruned Texas Sage (Silver and Green Cloud varieties) which have been removed. This area was not irrigated for many years, with the plants subsisting on incidental precipitation and irrigation diffusion from neighbors’ lots. The irrigation to this area has been repaired, and a large ornamental and small productive garden is now planned to be planted there. Are there any good resources, preferably more up to date than 1985, that can provide more information on local soil series and how to mitigate the inhospitable qualities of such?

A. You live in the Pittman area of Las Vegas and Henderson. 

Description of the Pittman soil series in Las Vegas and Henderson, NV.

Most native soils in that area are classified usually as “heavy” which means they have quite a bit of clay and smaller silt particles. Water drainage can be a problem in these soils if the soil is irrigated too often. For this reason, I tell people that if all the water in a hole on the property drains overnight, it’s okay. If this were Wisconsin or Iowa then it would be different. Those soils are beautiful compared to the Mojave Desert soils.

The soils for subdivisions oftentimes are imported or man-made and may not represent the native soils in those areas. If you have in imported soil on your property, then it may not be representative of the soils map. I am very familiar with NRCS soils maps for Southern Nevada and Northern Arizona, and I know the McCarran soil series quite well. It represents a huge area. So, make sure you are actually dealing with the native soil and not one that’s imported. You should be able to see that from the soil horizons. But overnight drainage for landscape soil would be okay for most landscape plants. This may not be true of Mojave native plants. If you are growing Mojave natives then I would suggest either not using an irrigation controller or using it only to water manually and not leave it on a schedule.

As far as more information is concerned, Dr. Dale Devitt (soil science researcher) and I are in the process of publishing a book that you might take a look at. It’s available on Amazon in digital form. If you want a hard copy or digital it is also available from the publisher. Dr. Devitt teaches in the biology department at UNLV. Dr. Devitt is a “hard” scientist and I consider myself a “soft” scientist who focuses mostly on transferring difficult information in terms more easily understood. Together we have published about 40 peer-reviewed scientific research articles in various journals. 

Dr. Devitt is the local soils expert and knows more than anyone about soils and water movement and plant use in the Mojave Desert. But honestly the book takes much of this difficult information from an urban tree perspective and tries to simplify it as much as possible. It’s really rehashing a lot of the same information but puts it into one book.

Any of the Cloud series of native plants (Green Cloud, Silver Cloud, etc.) will be sensitive to soils that drain poorly. Their roots will tend to die due to poor drainage. In soils like that, consider planting them on a hill or berm about a foot tall and perhaps about six feet wide. This will give the roots a chance to grow in a raised soil that will drain better.

Selecting Plants for Shade

Q. What plants can I plant in my front and backyards? I want plants that grow large enough to produce shade.

No shade on this south facing wall of this home. Wow, its hot! Shade the walls of this house to reduce electricity use in the summer. If they are deciduous then the sun can warm this house with sunlight in the winter. Shade the walls and windows. That is all that is needed, Not the roof.

A. Shade only what’s needed. This is usually the West and South windows and walls. A single-story home only needs, at the most, 25 foot-tall trees or shrubs. A two-story home can handle trees to about 35 or 40 feet tall maximum. Selecting trees taller than needed just looks “funny” when they are mature. Big trees need big spaces like parks and malls to look good.

Select Trees by Low Temperature

Winter low temperatures should be the deciding factor for permanent trees and shrubs important to the design of the landscape. There are plants used for “fun”. Fun plants can be selected for any low winter temperature. But expect damage or lose them during cold winters. In the Las Vegas Valley, use a winter temperature around 20°F minimum for the most important trees and shrubs in a landscape.

               To see which plants are available. There are three choices; buying from a local nursery or garden center, taking a road trip to buy plants, or purchasing plants online. Buying online starts around October with shipments beginning in January for spring planting of winter hardy plants. Plants bought online won’t have any soil around the roots so more care at planting time is needed.

            To aid your search for the right plant, use two places online; the plant database from the Southern Nevada water Authority or Arizona State University’s (ASU) plant database by Dr. Chris Martin. To access ASU’s plant database, type in the plants “common name” followed by “ASU”. To access Southern Nevada Water Authority’s database, start by typing in “SNWA” and “searchable database”. Pick 3 to 5 different plants in the case the plant you want is not available.

Interpreting Mojave Desert Soil though Native Plant Growth

Q. If anything, what can the different species of weeds tell someone about the soil conditions they’re found in. For example, do dandelions only grow in certain pH ranges or does puncturevine thrive only in certain sodic concentrations etc. etc.? I want to understand the most about my land via the plants that grow on it unassisted.

I apologize for the lousy picture. I took it from a slide I had made a long time ago. This is Lake Mead and showing the change in native plants (weeds) that occur with a change in soil moisture. Plants are very different closer to the Lake than further away due to less available soil moisture. As soil moisture changes, the plant communities change as well as their numbers (density) and sometimes even their height depending on the plants.

A. Which weeds are growing on native soil or disturb soils can tell you a lot. It can give hints about the chemistry of the soil and it will tell you a lot about its structure, if the soil has been disturbed or not, suitability for different plants and availability of water. 

I look at the type of weeds growing, the number of weeds and how tall they are. Wherever there is subsurface water there are a lot more plants per square meter and they are usually taller. Native soils high in phosphorus tend to favor those plants that flower more and produce seed. Crappy local native soils don’t grow much of anything. 

Dandelions for instance like disturbed soils, high phosphorus soils and they are very good at competition that’s one reason they can survive in lawns while common Bermudagrass does not. How the local plant community and the soil is managed influences which weeds grow. There are plants such as salt cedar which does favor growing in soils high in salinity but I’ve not seen a reference to sodic soils. That could be a question you could pose to Dr. Devitt. 

Some research questions I wanted to ask include different amounts of irrigation applied to a soil and how it influences native plant management and the value of soil amendments such as compost in influencing the management of native and exotic plants. To my knowledge none of those questions have been answered. Our soils typically are not classified as sodic soils but there are pockets (areas) of them in the valley. There are also pockets of high boron (a soil salt).

What Does "Winter-Deciduous" Mean?

 Other terms used besides Winter Deciduous include semi evergreen. It just means when it gets cold enough, it might drop its leaves because they get damaged by freezing weather, In warmer climates than Las Vegas, or if Las Vegas gets a winter with little to no freezing temperatures, then the leaves aren't damaged by the cold and they don't get damaged or may not drop. 

A change in leaf color to a "bronzing" yellowish brown can also occur. This is also a signal that it got cold. 

To reduce the chance of freezing damage, stop applying fertilizers to plants by around July 1.

This winter air temperature became so cold in this North Las Vegas location that this mesquite tree leaves were damaged, but not the tree, and they dropped. This tree, sometimes also called semi-evergreen, became deciduous.

If it gets cold enough, plants like this Star Jasmine will get yellow or bronze leaves and may even get deciduous.

Sago palm can also get cold damage during the winter if temperatures get low enough.

Bottlebrush can also get damaged from cold if winter temperatures are low enough.

Cold or freezing damage can also occur to some plants like this myoporum (locally called Australian Racer). It depends on how cold it got and for how long.

Part Time Vegetable and Herb Gardener Wanted in Las Vegas

 

Orchard at Ahern in Las Vegas

The Orchard at Ahern, located 1 ½ miles from Las Vegas Boulevard near the Center of Las Vegas, is looking for a responsible, experienced gardener, part time, to care for its vegetable and herb growing area. Ahern also owns and operates the Ahern Hotel in Las Vegas. The successful candidate would report to a Senior VP at Ahern and be responsible for the planting, growing, harvesting, and distribution of vegetables and herbs from its garden. Hours are flexible and the salary is negotiable. Interested individuals should contact Bob Morris at Extremehort@aol.com with their contact information and experience.