Grass Removal Mandates and Landscape Water Use

Q. Because we are an HOA, we are mandated to remove the grass surrounding our condos.  We have over 100 mature trees. What is the best irrigation to put on these trees after the grass is removed?  We want to save as many trees as possible. My particular unit had the grass removed many years ago and I have a large pine tree.  It is irrigated with drip emitters surrounding the tree about 4 feet from the trunk.  It is doing fine.

There are lots of reasons why large pine trees do well when the lawn is removed and drip irrigation is installed. Notice shrubs irrigated nearby. They need water as well and may be feeding the tree water.

A. Yes, lawns are big water users. Some types of grass (tall fescue in particular) needs daily watering during the summer and use about 7 feet of water (7 x 12 = 84 inches of water) each year to look good and lush. Bermudagrass lawns use less; about 4 and a half feet of water (54 inches) each year. Less, but still not low enough. We want to get our total landscape water use averaging around two feet of water each year. It makes sense that lawns are targeted because of their higher water use.

Newly planted Chinese pistache in a lawn. The roots of this tree will grow more shallow to accommodate the frequent lawn watering and other shallow rooted plants growing at its base.

t is not only HOAs. Any entity that has property is required to conserve water by removing lawns.  I would also include trees too large for the area and “out of scale” with the home. Just substituting lower water use plants, and finding a lower water use irrigation system alone, does not work. You will lose some trees, particularly the large ones.

Pine trees with adequate water will be full and the limbs will be growing strong.

Do you want to choose where water is applied or have someone decide for you? Lowering total landscape water use requires finding a balance between open areas that need no irrigation with areas that require irrigation. Total landscape water use is finding a suitable balance between the two. A less complicated reduction in total water use is finding a balance where water it is needed and where it is not.

Growth of pine trees comes from the ends, terminal buds. The new growth should be, in older pine trees, average about 10 to 12 inches.

Your landscape committee should be charged with identifying zero water use areas. Filling these areas may include the use of statuary, murals, paintings, gazebos, etc. They don’t need water. Start by identifying areas where loss of plants is not as important as other places. As these places eliminate the need for water, substitute statuaries, murals, paintings or gazebos that need no water but still beautify.

Landscape art (no water) should draw your attention. It can substitute for a lack of plants that need water. Landscape art can be an investment. 

Next, shade the south and west sides of buildings to prevent overheating of these units during the summer. Use deciduous trees for solar heating during the winter. Consider removing large plants on the north and east sides of buildings that have little function in heating or cooling the home. If plants remain or you find other plants, concentrate on smaller plants (less than 20 feet tall for single story homes) that use less water. Water the remaining trees and shrubs in irrigation “clusters” for ease of water delivery and finding leaks.

Even though it may be considered a desert tree, if it's not needed or the size is too large for the spot, get rid of it of make is smaller to save water.

            Water savings come from the “averaging” of water use over the property and the creation of non-irrigated “open” spaces. You can have your cake and eat it to but not everywhere! These open spaces instead may use statuaries, murals, paintings and gazebos that don’t use water.

This west side of a hospital in Parker, Arizona, shaded the windows and walls with low water use trees that don't get all that big. The rest of the landscape uses minimal water.

Where to Get Free Woodchips in Las Vegas?

Q. In one of your previous articles you mentioned free woodchips. Where do you go to get them?

Woodchips are different from bark chips. Bark chips are prettier, but they float and blow away in moderate wind. Woodchips don't do that. They don't easily blow away (I have personally seen them withstand 70 mph gusts) or float. Woodchips should be applied at least 2 - 3 inches deep to control weeds and conserve water. Woodchips rot into the soil (where its wet) and improve it by increasing its organic matter content.

A. You have to travel to North Las Vegas, but you can get a pick up load or trash bag full from the University Orchard. Call 702-257-5555 and get an update from the Master Gardeners regarding woodchip availability and what days and hours to get them. Woodchips are usually available on Tuesdays, Thursdays and Saturdays in the mornings (except holidays). Woodchips are usually available in North Las Vegas (in the Aliante area) about 100 yards east of North Decatur and Horse Drive at the Center for Urban Water Conservation.

Bark chips or bark mulch floats in water and blows in the wind. It resists soil rotting. It is inferior to woodchips (chopped up) from the entire tree.

             Woodchips are different from bark chips. Bark chips blow in the wind, resist soil decay and are water proof. Woodchips are made from grinding the entire tree so it can be taken to the dump. Yes, it includes bark woodchips but it is a smaller percentage of the chips and it is mixed together. Woodchips includes ALL of the tree ground up into woodchips, not just the bark. 

The weed in the picture is perennial nightshade and, along with bermudagrass, will grow through the woodchip mulch. Why? Because they are perennial and push through two inch mulch. Most weeds controlled by a surface mulch like woodchips are annual weeds. Most first weeds are are annuals.

             Bark woodchips are pretty. They make a prettier looking surface mulch. If you want your surface mulch to look pretty, then use a bark mulch. Or use both separated in layers. 

Bark chip (bark mulch) doesn't rot as easily as woodchips because the bark is made to be weather resistant.

            Tree woodchips are not as pretty but functional. When laid on top of the soil in a layer at least two inches thick it saves water, controls most weeds and improves the soil.

This is what can happen if mulch is not used. Annual and perennial weeds have a field day growing. No competition for sunlight, air and water! Weeds have a field day.

            Organics in our desert soil is severely lacking. To rot woodchip mulch takes water. Water and organics in the soil are linked. More water applied, more organics in the soil. Most trees and lawns require at least 2% organics in the soil. Vegetables need more, usually closer to 8% for quality vegetables. 

Map of the US soil organic matter content (scientists call it soil carbon content) https://extension.umn.edu/soil-management-and-health/soil-organic-matter-cropping-systems

How to judge if your soil has organics in it? Use the color first. If your soil is very low in organics it will be closer to light brown or even tan in color. If organics are present, desert soils become darker and start develop some structure. The higher the ‘organic content” in the soil, the darker its color. If a soil has 2% organics in it, it has a color similar coffee with a creamer in it. If it has 8% organics, it is a “chocolate brown” in color.

Mojave desert landscape soil in Las Vegas, Nevada

Visually is how to judge if organics should be applied to Mojave desert soils or not. In most Mojave desert soils, we judge a soils “organic content” from its darker color. That’s because it starts off light tan in color. If your soil has a darker color and you can make “dirt bombs”, then adding organics such as woodchips won’t help much when planting trees and shrubs. But that organic content may not be suitable for growing quality vegetables without compost added.

A method to use to judge soil organic content is the color of the soil. This is a jar test of a desert soil.

Vegetable Seed Use and Storage

Q. I have some old vegetable seed that I planted. I was told I wasted my money and time. Do you think I did?

Vegetable seed storage for longevity depends on which seed or cuttings depending on the vegetables but maintaining an appropriate temperature and low humidity are important.

A. It depends on the seed, how it was stored and how old it was. Usually, large seed doesn’t store as long as smaller seed; maybe two or three years. Small seed might store for 5 or 6 years or longer.

            The best temperature and humidity to store seed totals less than 100. That is directly from the National Seed Storage Lab in Ft. Collins, Co. For instance, if the temperature that they were stored totaled about 70F, then the humidity should be less than 30%. If the humidity was 70%, then the temperature needs to average around 30F. Of course the best temperature and humidity for seed storage is close to freezing for temperate seed. Having them both total less than 100 is suitable for a couple of years.

            When using old seed, plant two and expect one to live is a good motto.

            When storing seed, I try to keep the temperature and humidity of vegetable seed as low as possible. I stay away from buying seed exposed to heat or direct sunlight. I use a desiccant (corn starch works okay), put them in a glass jar with a screw lid, and put them in the fridge. They will keep this way for several to many years depending on the oil content of the seed. Small seed (e.g., tomato, eggplant, beet, carrot) usually has less oil in it than larger seed (e.g., beans, corn).

Grape Bunch Diseases are Now Here

Q. I am a big fan of your (Las Vegas Review Journal newspaper) column, but I haven’t seen any answers about what’s happening to my grapes. Please advise. This the stuff isn’t on all my grapes. I have four plants and maybe 10-15% have this white stuff on certain bunches.

This is what are called collectively, "bunch diseases". But are usually either Botrytis or powdery mildew.

A. I thought this might happen mostly because of our wet spring. Bayer tells us, when treating for grape bunch diseases, that about half of the improvement is due to better air circulation and the other half using a copper-based fungicide. They are right! Collectively, both botrytis and powdery mildew are called “bunch diseases”. Warning. Grapes must be present on the label because of testing and recommendations concerning the rate of application.

Sometimes, months after we see the disease during wet weather, the bunch disease shows up as dried berries. Too late to do much about it now.

            This looks like one of the grape diseases, probably grape botrytis or downy mildew. Try removing bunches and leaves so that you have one bunch every foot. If it is tight with leaves, remove some of the leaves as well. Don’t remove too many leaves so that you get direct sunlight on the grapes or limbs. You want to improve the air circulation around the bunches and the berries but without putting the bunches (and limbs) in direct strong sunlight for any length of time.

In severe cases, the grape bunch may just dry up!

            You can apply a spray mixture of a copper-based fungicide according to the label. Copper sulfate, Liqui-Cop, and Bordeaux sprays come to mind, but any copper-based fungicide should work. You may have to repeat the application. Read the label. Remember fungicides help stop plant diseases but do not “cure” the plant of a particular disease. You are spraying to prevent the spread of grape botrytis and powdery mildew. There is some evidence that Neem oil has given some protection, but copper-based fungicides are better.

One of the copper-based fungicides. Any fungicide that contains copper in it is considered a "copper-based" fungicide. https://www.gardeningknowhow.com/garden-how-to/info/what-is-copper-fungicide.htm

            You may be too late with this application, but it is worth a try. Do it very soon and follow label directions for controlling these “bunch diseases” on grapes.

Pruning Shrubs Correctly

Q. Attached you will see my 25-year-old bottle brush bush. As you can see, it needs some attention. Can I shape it a bit by trimming it back without harming it? The only trimming I have done is clipping off brown ends each spring (none this year) caused by winter cold. It displays beautiful color for several weeks when the weather warms up.

25 year old Bottle brush shrub

A. Yes but be careful and don’t let the landscape maintenance clods ruin the plant by shearing it with a hedge shears. You may want to consider separation between branches or removing offending branches altogether. It requires either cutting the plant to the ground OR selectively removing some of the older stems. Whether it produces suckers or not will tell you which way to prune it. Either way requires deep pruning cuts, not using a hedge shears.  

         Never use a hedge shears unless you want to replace the shrub in a few years. Hedge shears are for pruning a hedge. That's why the tool used is called a "hedge shears"! If it flowers in the spring, then prune it immediately after it finishes flowering so it has time to grow and produce wood for new flowers.

Formal hedges require quite a bit of work and time. Because they are formal, attention needs to be spent on them once a month. Anything growing "out of place" is cut back with a hedges shears. https://www.hedgesonline.co.uk/formal-hedging

An informal hedge accomplishes the same thing but with far less work. https://laidbackgardener.blog/2016/06/29/a-hedge-for-laidback-gardeners/

            In your case, use a hand pruners and snip three or four branches from each side of the plant, deep inside it, and select where to open it up. Hide your pruning cuts at least 12 to 18 inches inside your shrub. Reach deep inside your shrub. There are several places to prune. Move your hand to each crotch. Ask yourself, "If I were to remove that stem, how would it look?"

           Because it’s so dense on all sides, “cut at a crotch” and remove an entire offending branch or stem. Concentrate on removing stems or branches that are growing down or up. From each section of the shrub remove a stem so the remaining branches are more open and can “breathe”. Remove no more than about ¼ of the branches every three years or so. It will not need more than that.

Pruning with a hedge shears may look okay when the shrub is young, but as it gets older the shrubs older wood needs to be removed. This requires a few well-placed cuts deep inside the shrub.

            When you are finished pruning, the shrub it should look like it was never pruned. That’s the mark of a good pruning job. Who wants to look at an ugly shrub until it grows back? Also spring is the time to apply an iron fertilizer/chelate to the soil to cure the yellowing that occurs on this plant.