If You Want it Green, You Will Like 'Australian Racer'

Q. A neighbor suggested we look closely at Australian racer. It stays low and is green. Seeing it in place, we like it. What are your thoughts about it?

Myoporum, or Australian Racer as it is known by local nurseries, was a ground cover substitute. As it got larger it would frequently die in the center after a few years. Its major problems are spider mites and root rot from watering it too often.

A. “Australian racer” (Myoporum parvifolium) works as a sprawling groundcover as long as you don’t walk on it. It spreads in every direction about 6 feet or more (space plants at least 6 feet apart) but not considered a “desert plant” (mesic, not xeric). It handles the high and low temperatures of Las Vegas and used to be quite popular. It uses less water than a lawn but should not be watered every day. Ever. Water it as frequently as a fruit tree or eucalyptus.

https://www.public.asu.edu/~camartin/plants/Plant%20html%20files/myoporumparvifolium.html

            It’s negatives? If it’s watered daily, it will definitely get root rot and die. Watch this plant for spider mites during the heat. It can also be short-lived (maybe 15 to 20 years). When it is about 5 to 7 years old, cut the long and thick stems back or it develops stems without leaves toward the center. Use three to four drip emitters and wet the roots to about 18 inches deep.

Roots of Plants Growing in Desert Landscapes

           Roots of plants do not grow separately. They grow together, all mixed up. Roots search for open spaces that are wet. They use the water for irrigated neighboring plants. Before now, we used to assess all the different plants’ water use and then add them together. Collectively they made up water needed by a landscape. But now, because we can’t separate the roots, we estimate the water use of a total landscape, not each individual plant and add them up.

I fruit tree growing in a lawn obviously has roots which are mixed with the lawn. What do we water? We water for the lawn, not the fruit tree. Consequently the fruit tree will grow roots in the same soil space lawn roots grow.

Plant roots growing in the desert follow water. Not entirely true because they're looking for air as well. Air and water. A mixture. Ask any person growing in hydroponics. But water is their principal need. With rainfall it’s a lot easier. With rainfall, spinning a circle with an established plant lying horizontally, roughly describes where you can find its roots. In the desert it’s not that easy. The first rule of plants growing in the desert is that roots will follow water! Where water is applied, you will find the roots of plants.

The roots of plants are roughly proportional to the height and width of the top of the plant if they get plenty of rain and the soil drains.
https://www.openculture.com/2022/01/1100-delicate-drawings-of-root-systems-reveals-the-hidden-world-of-plants.html

Plant roots are lazy. They use first, water that’s the easiest to get. The easier the water is to get at, the better. This is why trees growing in lawns have a mass of shallow roots! It’s difficult to get roots to grow deeper than “lawn water” but necessary. Shallow watering, as in a lawn, produces trees and shrubs with shallow roots. Tree and shrub root can grow deeper but they don’t have to. Trees and shrubs with roots deeper than the lawn are necessary. Deeper roots tolerate summer heat better.

Trees growing in lawns have a mixture in the soil of lawn grass roots and tree roots.

It's because we water for lawn, not the tree.

How to get deeper roots in Las Vegas? First, remove the lawn during cooler weather, starting in early fall and later. Use the weather app on your phone. September is usually okay but don’t remove lawns during June, July and August which are typically our hottest months. Secondly, move the irrigation emitters that are near the trunk. Soils are different but drip emitters starting 12 to 18 inches from the trunk are close enough. Emitters spaced 18 inches or more under at least half of the canopy is usually enough. As these trees and shrubs get bigger, they will require extra emitters. Space extra emitters the same as the others.

There is a river a couple hundred yards from this mesquite tree. Tree roots go after water only if the soil is wet nearby.

Avoid watering daily. It’s not necessary and it works against you. Every landscape is different, but there are normally only three types of plants that require daily irrigation in the summer: lawns, vegetables and annual flowers. Give trees and shrubs at least one day of “rest” (without water) before watering again. Do you want your plants to have shallow roots or deep roots? 

Native Desert Soil Is Productive for Vegetables

Q. My garden area is about 40 feet long x 40 feet wide. The soil is native. How much compost do I need?

You will need at least a truckload, that's 2 cubic yards. Continue to add compost as it needs it, probably every one to two years.

A. If this is a light tan native soil, you will need between about 1 inch of compost, during its first year, laid on the top of this native soil and rototilled to a depth of 8 to 12 inches. You would need to order about 3 cubic yards of compost to accomplish this. If you are ordering by weight this amount of compost totals about 4500 pounds, but its weight depends on its degree of wetness. A standard pickup truck will carry about 2 cubic yards, dry, to give you an idea. In the following years one pickup load every one or two years will be plenty to boost production.

Basil is growing with a rich compost and no extra fertilizer is needed. Straw is used as a mulch to conserve water and keep the soil cool. Native desert soil is used an enriched with compost.

Depending on how “rich” the compost is, a small bag of starter fertilizer high in phosphorus (the middle number) may or may not be needed by rototilling, or soil mixing with a shovel, compost to that depth.

These are very large plots growing eggplant in compost amended native desert soil with drip irrigation. These raised beds are without sidewalls, just the natural slope of the soil keeps it together.

After the compost has been rototilled and water applied to this amended soil, the soil will become darker brown in color. Approximately one pickup load will need to be added to this area every year, or every other year, depending upon the garden soil texture and color. During the first season of growth, the amended native soil will be productive. It will take about three seasons of growth and watering before the soil is highly productive, each season getting better.

Don’t walk on this soil except for planting and harvesting. Instead, created walkways between growing areas should be shoveled about 18 – 24 inches wide and the garden soil leveled. No sidewalls need to be constructed in this set up.

Cutting the Roots of Asparagus for Planting Among Fruit Trees

Q. I see online some people cut the roots of asparagus before planting. I did this last year. Is it a good idea? I was thinking of planting asparagus at the base of fruit trees. It makes them easier to plant, but are there consequences?

Asparagus can get 5 feet tall or taller after harvest.

A. Your question is about cutting the roots of asparagus and what consequences might occur. I must guess since I don’t have much experience with that. They are both deep-rooted, so I don’t think there is a problem with irrigation and spear production provided the roots are covered with clean (no rocks) soil when replanted. It’s best to use clean soil directly above the roots. Rocky soil covering the roots may lead to the growth of “crooked spears”. The crown of asparagus will have to grow some new roots for storage.

There is one major problem. It has to do with interference between the fruit tree and the asparagus. After the asparagus has been harvested, the shoots are allowed to “fern” up so they can gather energy for next year’s production and the roots can grow. These ferns can be 5 to 6 feet tall when they finish growing. I could see how these might grow up into the branches of the fruit trees. Ferns can be cut without any problems. Cutting the ferns will interfere slightly with the number spears you collect in the spring, but not much.

Shade can be a problem when fruit trees are grown close together. This happens after about 4 to 6 years and it may be too dark for some plants.

A minor problem (maybe??) is the amount of light available. As the fruit trees get larger, they will create more shade. The ferns will not collect as much sunlight in this location. Regarding the asparagus crowns competing with the fruit tree for “root space”, it’s true but not a huge problem if you don’t put too many crowns at the base of the tree and plant them where they will get light in the future. I think you are fine with 3 to 4 crowns planted there about 18 inches or so apart.

'Iceberg' Roses are Older But Worth Planting in Las Vegas

Q. This may be a bit too amateurish for your column, but I need help with 'Iceberg' roses. I pulled the rock away and fertilized this past spring. I thought the roses I planted in pots would do better, but they don’t.  I ask the nurseries when I go but get conflicting information. Why are there holes in the flowers?  When I see dark leaves that look diseased, I pull them off.  When I deadhead and trim back (5 sets of leaves), I sanitize the shears to not spread any potential disease from bush to bush.  Is there anything else you see?

Iceberg roses are an older rose but still valuable for planting in Las Vegas.

A. Whenever I hear roses, my thoughts go to plant location relative to the house and soil enrichment. They are the most important. Make sure that any type of rose is a good 3 to 4 feet from any hot wall. Roses grow best in full sunlight with plenty of air movement or on East or North sides of homes in the hot Mojave Desert.

            During the planting season (never summer), the soil should be amended with compost and covered with a 2 to 3-inch layer of wood chips. The best woodchips to use are those that are chipped from local trees rather than a “bark” mulch.

The true iceberg rose is a floribunda type that is worthy of containers in Las Vegas.

Here it's planted in a container but the soil must be changed, or at least renewed, every three or four years.

            The old-fashioned “Iceberg” rose is a bush rose (considered a Floribunda type), 3 to 4 foot tall and bearing medium-sized, white flowers in the spring and fall months here. Iceberg roses are pruned at the same time as other roses, usually in late January. The iceberg rose has been bred to be a climber (10 to 12 feet) in more recent years with the same color flowers and scent as the original 1958 rose.

           I don't see a problem with this Rose except a lack of fertilizer and water. Diseases and insects of roses in our Mojave desert climate include powdery mildew, iron deficiency, bacterial galls, spider mites, thrips, and cane borers. Try fertilizing 3 to 4 times each year during the cool months, in the first fertilizer application (spring) include an iron fertilizer, and water the plant twice a day during the heat of the summer months and it's in a small container. If you suspect an insect or disease, ask for a Rosarian on the Master Gardener helpline, describe the problem you are having with your roses and follow their advice.

Roots of Trees Follow the Water in the Desert

Q. You posted pictures about watering with the depth of a plants root system. How do trees survive in lawns then?

Suggested root depth of different plants and how much water to give them. This makes it easier to see that taller plants have deeper roots and need to be watered as such. As the roots get deeper they also get wider. This is why big trees use more water than little trees.  https://wateruseitwisely.com/saving-water-outdoors/plant-watering-guide/

A. Some trees survive in lawns and others don’t. As a rule of thumb, mesic (nondesert) trees will survive in lawns while xeric (desert) trees will not. For instance, ash trees (mesic) will survive in a lawn. Xeric (desert) trees will die if they receive water too often. Xeric trees such as Foothills Palo Verde will struggle in a lawn. Mesic trees are better suited for lawn areas than xeric trees.

Roots of trees will go where there is plenty of water even if it's in you or your neighbor's yard. It goes without saying that large trees should not be planted close to walls.

Plants are lazy, including their roots. Roots grow best where can get water mixed with air and get it the easiest. That concept pertains to both mesic and xeric trees. Daily watering during the summer means the roots of (mostly) mesic trees growing in a lawn area will have roots all through the soil surface. There they can get a mixture of both air and water the easiest.

Roots growing in lawns well head to the surface of the lawn because that's where they find a good mixture of air, water, and fertilizer.

Removing the lawn also removes this distribution of water and air. Instead, these trees must survive on the water provided through drip emitters. That is a change from watering the lawn to watering shrubs. Is that enough water? Is the water provided in the right distribution? Is the water provided to the tree in the right spots? You will find out usually next summer when it gets hot. By the way, surface mulch (rock or wood chips) helps stop the water from evaporating from the soil during the heat of the day.

Golf course superintendents well water new trees with a water truck even if they're growing in grass.

Besides water, roots of tall pine trees provide stability for the tree during wind. A general rule of thumb is to water deeply according to its height. For instance, tall trees growing without a lawn should be watered to a depth of 3 feet to provide the tree stability during windy weather.

How to Get Rid of Snails in a Lawn

Q. I have some snails in my lawn. How do I get rid of them?

Snails like it wet and darker than most lawns.

A. The best way to control snails (or slugs) in lawns is to give the lawn more light. Snails hate light but they like to eat!  Snails and slugs eat young plants and microscopic plants such as “large enough to see” algae.

The worst situation for snails and slugs is lawns growing under trees producing shade. The bigger and denser the tree gets, the more shade it produces.

Dappled shade produced by the branches of trees may need to be thinned if it gets too dense. Snails and slugs hate sunlight, prefer shade, and wet soil. Right now there is enough light for the lawn as well as snails and slugs....if the lawn is kept wet.

In cases like that, get rid of the lawn, or both, but in the desert never favor the lawn over the tree. A good-looking fescue lawn uses a lot more water than nearly any tree and usually requires daily applications of water in the summer. Fescue lawns in the shade of a tree might still need 6 or more feet of water annually to look good. Many of our trees in full sun will need anywhere from two to 5 feet of water applied under their canopy. Xeric trees like acacia need less water, annually, than mesic trees like pistache or vitex.

Snails and slugs in lawns

There are baits made for snails and slugs. Those baits usually contain iron phosphate which is low in human toxicity. But it is a pesticide.

Sluggo is the old tried and true chemical control for snails and slugs.

If you are into organics, then you might not want to use Sluggo. Your only options are to increase the light and trapping. During times of high light levels snails and slugs look for places to “hide” so laying out boards or other places so they can hide during the day provide places where they “collect”. Their numbers can be reduced if you are willing to dispose of them after they collect during the day such as under something.

Temperate Fruit Trees Like it Colder and Moist

Q. I was in Moab, Utah, when I ran across this apricot tree. It’s doing very well. I'm guessing the reason they are doing so well is because of the high organic levels in the soil and cooler temperatures?

Temperate fruit trees like apricot, peach, nectarine, plum and apple prefer cooler weather that elevation provides, organics in the soil, and watering like any other mesic tree.

A. You're right. Fruit trees prefer to grow in soils with higher organics than most desert soils unless those desert soils were “farmed” and extra water was needed for farming.

Fruit trees also prefer to grow in cooler temperatures than provided by hot deserts. At about 4000 feet of elevation, the Moab area is higher in elevation, so it has cooler temperatures than our 2000 to 3000 foot elevations.

Growing of citrus though, in either location, is borderline. Moab is still worse than our 2000 feet of elevation. Neither place is like Yuma or Riverside for citrus.

Vitex or Monk's Pepper is Not Xeric but Mesic

Q. Our vitex has done well for over 20 years but it is starting to thin out. What gives?

Vitex or Monk's Pepper tree is mesic in its water use. Similar to oleander, it prefers to grow under mesic conditions (can handle a lawn for instance) but can also handles dry soil, to an extent. It prefers a fruit tree water environment so it can handle a  well-drained lawn.

A. Hard to get blue flowers anywhere. Well Vitex, or Monk’s pepper, is a mesic tree that can have blue or white flowers. Yes, it is a mesic tree and not from the desert but it still is considered low in its water use. It is from Mediterranean regions like oleander and European olive. But it’s one of those strange “cats” that doesn’t like poorly drained lawns. It can’t handle drainage problems very well.

20 foot tree for the Phoenix area

That may be the source of your problem with that tree. If the tree was planted in a low spot and, if all this rain added even more water to this low spot, on top of your irrigations, then water-soaked roots during the heat may be the source of your problem. Summer heat is more of a problem than cold weather regarding rotting roots.

Recommendations but be careful planting in the desert, its different

I was reading recently that vitex can be a short-lived tree. 20 years was the maximum life it was given in this reference. I don’t know if I agree, but you can winter prune it and extend its life. Trees, particularly small trees like vitex, can have an extended life by heavily pruning it in the winter. Many trees have a “root to shoot” ratio and the new growth will come back like gangbusters until that old root to shoot ratio is reached.

Contrasting the information above, adding some compost to the soil at planting time can will make this tree live longer. Don't be afraid of doing this. Amend the soil with compost at planting, water it like you would any other landscape tree. Prune it so that the trunk shades itself.

Lightly fertilize it in the early spring with a fertilizer containing lots of nutrients including nitrogen.

Japanese Blueberry in Las Vegas Landscapes

Q. A local tree guide does not recommend planting Japanese blueberry because of “environmental challenges”. We had one at our old house and it was fine. It is the right size and shape for a spot we are considering.

Young Japanese blueberry. It does not like the heat and isolation in Las Vegas landscapes. It prefers to be on the north or east sides of a home and surrounded by other plants that need water. The burlap bags on their head is to prevent them from getting sun damage.

A. It gets pretty big over time. There are some things that favor it and some things that are not in favor of it. Let’s explore.

Water use. In the desert this should be a concern with any plant we are thinking about. The fewer but important plants the better. It is mesic in its water use. It should be watered at the same time as other mesic plants. Try not to water xeric plants at the same time as mesic plants. Xeric (or desert) plants are watered less often than mesic (nondesert) plants. That is one of the reasons xeric plants use less water.

Size. It’s slow growing but gets about the same size as European olive; 35x35.

East side. It doesn’t like afternoon sun. Too hot for it on the South and West sides. Likes the east side with afternoon shade and surrounded by other plants that need watering. That and its mature size are probably the reasons it is not liked much.

It is a low water using plant/shrub but not xeric. If you have the room for it and can afford the water then plant it. Put it on a water valve for mesic plants.

Recommended plants for the Phoenix area.

Wormy Apples a Problem with Honeycrisp Apples

Q. I have had wormy apples in our 'Honey Crisp' apple tree. Last year we had the same problem. I was told to spray a fungicide. I also sprayed Neem oil. I waited until the apples started to form. I still have these worms in every apple on my tree. HELP!!! 

This is codling moth stuck on the sticky side of a pheremone trap. It is about 3/8 inch long and a true moth. Since the adult is a moth, the juvenile or immature form is a "worm" or larva. When populations are large they produce "wormy apples".

 A. I am guessing that you are dealing with codling moth. This is a common pest of apples and pears. They appear as "wormy apples". They are creamy white and about 3/8 inch long when they are mature. Usually, they have a brown head. They start getting into the fruit when the fruit is small and may continue to feed as the fruit gets larger. You can read more about codling moth control by searching for "codling moth" and "IPM". 

https://ipm.ucanr.edu/PMG/PESTNOTES/pn7412.html

The most reliable site is from the University of California. If this is codling moth, then picking and get rid of small fruit which is infested is the first step. 

When the codling moth is flying, the moth will "sting" a small fruit causing it to drop. If it happens when the fruit is larger, it may stay on the tree. Look up for "stung" fruit or look at the ground for fallen fruit. Fruit produced later will have a larger percentage of stung fruit. Look for fruit tree species that are produced and harvested early. 

Otherwise, their population continues to increase as the apple stays on the tree longer. Apples that stay on the tree longest are the most heavily infested. On the flip side, apples harvested early are the least infested. Populations of this pest increase with each generation produced. In our climate, expect codling moth to have three or four generations each year so start getting rid of infested fruit when the fruit is small. With each generation the numbers of these moths will increase and increase as the year progresses. 

Start picking and getting rid of infested fruit starting about six weeks after it flowers. You can recognize infested fruit because of the brown frass coming out of it. The places where frass coming from the fruit are called "stings". Stings are egg-laying sites by the female moth. Fruit that has frass coming from it will either fall from the tree or stay on the tree and get "wormier". When you remove this fruit early, the population of “worms” has a better chance of staying low. 

As fruit gets older, the "worms" get bigger and tunnel into the fruit deeper. They might feed on the seeds of these fruit before they pupate into a moth.

 I have had good luck spraying either Bt or Spinosad several times over one season. Follow label directions. I have also had good luck if I use pheromone traps and get rid of them using these traps. I use one trap for every three or four trees. 

This codling moth has already exited. Notice the "frass" left behind when it exited.

Usually, pheremone traps are used for timing the application of sprays but when populations are low, I have had good luck “trapping them out”. Those traps should be put in the trees when the trees begin flowering or at least a couple weeks after they start to flower. Pheremone traps for codling moth can be bought from several places online. Look for them. The pheromone must be replaced regularly as per the instructions. Those wormy apples you got probably came from a neighbor who did not control them.

This is a winged trap. More popular are the three sided "delta traps". The winged traps, in my opinion, are better for repelling the moths. That is, better for using pheremones to keep fruit free of "worms". The pheromones have better air circulation in those kinds of traps, the pheremones must be changed out more regularly, and the traps more concentrated. The delta traps are best for monitoring moths and telling you when to spray pesticides.

When to Fertilize Cacti

Q. I have some cacti in my backyard.  Should I fertilize them and when?

When cacti flower they need high phosphorus fertilizer. A rose or tomato fertilizer should work.

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 cacti grow slowly, and other plants may or may not, depending on their “genetics”. For cacti, it depends on the fertilizer level, watering and soil mix besides their “genetics”.

There is one fertilizer exception and it is a bit tricky. Nitrogen fertilizers increase the speed at which any plant, including cacti, get larger but you must be careful. There is a danger from “growing too fast” for all plants including cacti. 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 cacti are growing well without it, then don’t use it.

How Does 'Little Miss Figgy' Perform in Southern Nevada?

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 which in the summer gets full sun, but which now is getting a lot of shade. Is that a dealbreaker for the fig?

I have never grown Little Miss Figgy in our climate but, like most figs, it should do well. It is smaller and may be suitable for container growing. The trend now is for smaller plants and earlier production. 

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 to 10 feet tall by 4 to 8 feet wide) and develops dark purple fruit with red “pulp” or interior. 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 it often enough when it starts into its second batch of fruit and temperatures are higher and therefore its water use is higher as the season gets warmer. Because it’s smaller, it should use less water (but not watered less often) when planted in the ground and can rely on other sources of water that the soil might provide.

Saving Water Through Landscape Design

           Designing a landscape for only energy conservation (an example is lowering the cost of running the air conditioner) is quite simple. All you must do is ask yourself, “Which sides of the home are the hottest?” Create shade on the walls and windows close to the house for these hot sides. Try not using plants when you do this. Use them if you must. Creating shade that doesn’t use water requires more “brainwork” but may be necessary in the desert. Usually, the hottest areas are the exposed South and West walls and windows of a home.

If you don’t know which sides are hot, use a “temperature gun” (infrared laser for measuring temperature) during the hottest times of the day. You can buy an inexpensive but accurate gun for less than $25. The hottest areas are typically handled by shading the walls and windows on these hot sides rather than shading the roof. Roofs are usually better insulated than the walls and, in particular, windows.

Selecting plants to save summer electrical cost is quite simple since shading the south and west walls and windows is most important. Select plants that are “winter deciduous” so that the sun warms the house during the winter months. If water is plentiful, how much water these plants use is not important. To lower electrical costs, regardless of water, always shade the hot walls and windows of a home.

Irrigation design is important. I can’t stress the importance of using “hydrozones”. Hydrozoning is when the valves control when to water plants. Xeric (desert) versus mesic (nondesert) plant water use relies on how frequently each are watered. Use mesic plants when water is provided to them at the same time. How deep plants are watered is adjustable by adding or subtracting drips. How frequently they are watered is not. 

Xeric plants are not watered as often as mesic plants if you want to conserve water. This means plants are matched to a specific irrigation valve; xeric plants are put on one valve and mesic plants are put on a separate valve. This means you must know the difference between xeric (desert) and mesic (nondesert) plants. Xeric or desert plants will grow more rapidly than mesic, or non-desert plants, if they are watered like mesic plants. That's just they way they are. Xeric plants are more “adjustable” in their growth if they are all watered at the same time, and you can adjust the frequency of watering. When mesic and xeric plants are placed on the same valve, mesic plants will signal you to water and not the other way around.

When water is scarce, xeric plants (desert plants) tolerate dry soil better than mesic plants. They have capabilities of saving water through many different traits including leaf drop, changes in leaf and plant size, as well as changes to the plant at the genetic/molecular level. Xeric plants handle water shortages more efficiently than mesic plants. Being from the desert, xeric plants have evolved to soil drought. Water xeric plants less often. This means watering them with a separate irrigation valve (hydrozones). Because of this, xeric plants can get by (and often benefit) when watered less frequently than mesic plants.

For instance, foothills (not Blue or ‘Desert Museum’) palo verde (Parkinsonia microphylla or Cercidium microphyllum, depending on the source of its scientific name) is a true xeric, desert, or low water use plant. It grows in flat, dry areas throughout the Sonoran Desert of the American southwest. It can survive in dry soil for long periods of time. They can’t survive without any water, but they will require watering, deeply, less often.

When water is limited, xeric plant growth first begins to slow or stop. That can be hard to see. Controlling their size, controls their water use. If dry soils continue, xeric plants start dropping their leaves. That is easier to see. Fewer leaves mean there are fewer leaves present to lose water. The canopy begins “thinning out.” It’s time to water! If the soil continues to remain dry, then remaining leaves begin scorching and branches begin dying. Plants are starting to look bad. In the case of cacti, their stems may begin to shrivel. You don’t want limb dieback, or cactus shriveling, in a landscape. That’s not pretty. On the flipside, they may not look the best when that dry spell is over, but at least they have survived! In a landscape, deeply watering these plants once every 4 to 8 weeks is usually enough. Observing xeric plants regularly (once a week in the summer) will tell you if it’s time to water or hold off.

Branch dieback in palo verde and other trees (mostly mesic) can be confused with the palo verde root borer. Occasionally a single, isolated branch will begin dying back to the trunk during the summer if these insects have been feeding on the roots. In cases like these, a systemic insecticide for borers might be the only solution available. As with other plants, apply this insecticide only after flowering to avoid the risk of hurting pollinators like honeybees.

How much water is applied is controlled by the size of the emitters (two-, three-, four-, or 5-gallon drip emitters) or a moat surrounding trees and shrubs. For 10- to 12-foot-tall trees, flat moats about 6 feet in diameter, and 2 to 3 inches tall, will work. Figure that in most level soils, 1 inch of water will wet roots about 15 to 18 inches deep. My experience tells me that at least half the area under the tree’s canopy should receive this water. Once the roots of a tree are watered deeply enough, the only changes that need to be made to an irrigation timer are seasonal.

If you try grow deep-rooted, xeric (desert) trees in a fescue lawn (called a mixed landscape which I don’t recommend), the tree frequently dies, or “wiggles” in the soil. This is because it is watered every day the tree may have a fungal disease called “root rot.” Xeric trees don’t need daily watering, like a lawn, in the summer. It’s watered every day because fescue lawn needs it, not because the trees need it. True xeric plants are very susceptible to root or collar rot.

Not true of Chinese pistache or bottle trees. We don’t know how much water these trees use but both trees are mesic (nondesert) in their water needs, not xeric. This means they can survive dry soil very well. However, both bottle trees and Chinese pistache, because they are used to handling more frequent watering, will do okay in lawns. Their roots will grow shallower because of the lawn, but they will survive.          

If you want to control the other applied to your landscape (or about 70% of the water used) then take control the irrigation timer. Once control is gained of the irrigation timer, the next steps are easier.

Black Spots on Octopus Agave Leaves

Q. Is there something we need to do for these spots on the leaves of my octopus agave?

A. I think this is a fungal disease that favors a higher humidity than we normally have in the desert. The disease was caused and spread by the rain and wind that we had earlier. You don't want any fungal disease spreading to the mainstem. To prevent that, you can apply a common landscape fungicide to the cactus after you have a repeat of the rain and wind event. Watch your weather app. If your weather app says the rain is returning, apply the landscape fungicide the day after it occurs.

Broad-based landscape fungicides are meant to prevent the spread of many different types of disease.

Fruit and vegetable growers use copper-based fungicides as a protectant for many different kinds of foliar diseases. To be used effectively, and like most fungicides, they must be applied before the presence of disease. Organic fungicides are the only organic option worthwhile against diseases such as late blight and downy mildew. Think tomatoes, peppers, eggplant, and potatoes. These diseases have the ability to kill plants. Copper is also an essential nutrient for plants but use it sparingly.

Copper fungicides, like this one from Bonide, help prevent widespread infections of many more diseases when they are caught early enough. When used occasionally, copper is also an essential minor element for plants.

In the meantime, prune out any black “spots” or lesions that you see in the stems. I think these are fungal lesions with dormant fungi waiting for the next rain event to make it active again. Sanitize between any cuts to eliminate re-infecting the plant. Use 70% ethyl alcohol to sanitize a knife or pruning shears. Using both the fungicide after wet weather and cutting out the black spots helps eliminate future problems.

Make sure you're not overwatering it and improve soil drainage around its roots. Octopus agave originates in the Sonoran Desert of Mexico therefore it doesn’t like getting watered too often. For instance, it will not survive in a lawn. Take it off the irrigation controller and hand water with a hose. Watering these plants once with a hose only gets the water 3 or 4 inches deep. Water these plants five times a year; only three or four times during the summer and once during the winter. The soil must be dry between waterings!

Fertilizing in the Fall?

Q. Is it too early to fertilize now my oleanders, lantana, rosemary, and chase tree?

This could be temperature, nitrogen or iron. Try different fertilizers. If you find the right fertilizer it will become darker and greener. That's how you know its a fertilizer problem.

A. You can fertilize now (October) and skip the spring application. Woody plants put nitrogen fertilizer (whatever is "left over") into “storage” until spring. The only plants you want to skip are the so-called “winter tender” plants which you don’t list (except the tops of lantana which are damaged at 32F). Those are the plants which are sensitive to winter cold damage and include most of our citrus and freeze tender plants like bougainvillea. You don’t want to stimulate new growth that could be damaged by freezing temperatures. This might include the more tender dwarf salmon colored flowered oleanders (5 foot and tender at 20F) but not the traditionally big ones like the reds and white flowered types (18 foot) which are cold hardy to about 10F.

            Skip fall soil applications of iron fertilizers and wait to correct yellowing due to iron in early spring. Plants will respond to soil applied iron fertilizers best in the early spring. Fall applications of iron fertilizers are best when sprayed on the leaves. Use liquid detergent like dishwashing soap or (best) use a spray surfactant such as a wetting agent when you spray. Also it is best to use distilled water so the pH is not alkaline or acid. Better for iron uptake by the plant through its leaves. Makes more iron available.

Different Types of Sago Palm (Cycad)

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 this.  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?

Even if sago palm (cycad is a better term, Cycas revoluta) is located on the north side of a home it still has a browning on the leaflet tips because of our low humidity. This sago palm can handle colder temperatures than other types.

A. First of all, the sago palm is not a palm at all. It is just called a type of palm which its not. Each sago palm has evolved different strategies to handle where they are from.

There are different types or species and even genera of sago palms. These are based upon 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 them small enough to qualify as an “indoor plant”.

This is a queen sago palm (Cycas circinalis) is from a large nursery in central India. It is native to southern India and grows about 12 feet tall and 12 feet wide in hot, humid climates.   https://www.naturenursery.in/product/queen-sago-palm/

            Sago palms come from a variety of climates but mostly tropical or semi tropical. Lots 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 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” or speckled light. They also prefer to grow in amended soils and not in rock mulch. Some of them like warmer climates than others. Each one has evolved differently.

            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”. I don't know which type you have but some are meant for interiors and not the winter cold outdoors. Be careful unless you know what you are looking for. Use the scientific or Latin name when possible. Sometimes nurseries will confuse them and sell you one that you are not expecting. Even the pros get it wrong sometimes.

Do Pine Needles Make a Good Compost?

Q. Should I leave the pine needles around the basin of the 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 on top of the needles.  My part-time gardener says I should keep them around the trees so that they act as a mulch.  Which is correct?

In the desert, pine needles mixed with other ingredients for compost, add nutrients to the soil. 

A. Your gardener is correct but in a reverse sense you are too! If you can stand leaving the pine needles in place, (they do not make the soil more acidic, and if they did, what’s wrong with that?) 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 nutrition and soil organic content. If there is 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.

Pine needles make a good compost even if they don't rot as easily as some other ingredients and, in desert soil where a lack of acidity is a problem, can maybe help to pH lower! A common problem reported has been that they create acidity when they rot. In the desert, who cares? Our soil needs it.

            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 ten 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).