When to Prune Wisteria Depends

Q. I read your blog on pruning flowering shrubs but want to know if this information also pertains to wisteria vines? I’ve read that flowering occurs on new growth, so I am not sure about trimming it.

A. In my blog I was telling people to differentiate between plants that flower early in the spring versus those that flower later in the spring. Bottom line, always prune flowering trees and shrubs any time after they finish flowering if flowering is important to you.

Let me first give you a textbook answer. Wisteria falls into two major groups; the Asian varieties and the western varieties. The Asian varieties of wisteria flower on last year's growth (early spring flowers) while the American or western varieties flower on current season growth (late spring or summer flowering).

Something interesting about wisteria is the amount of time the plant needs to begin flowering. It's usually quite a while. Some people say 10 years to initiate flowering, others say 15 years and I have even seen some people say 20 years! That's actually quite old for a woody plant to start flowering. Typically unimproved woody plants begin flowering in about 6 to 8 years. 

Plant breeding and producing hybrids that flower earlier can address this problem. When you're pruning try to leave as much older and larger wood as possible. Prune its structure the way you want it as early as possible. A few things that can affect how soon or at what age the plant begins flowering can be removing too much larger wood, using a lot of high nitrogen fertilizers, how much shade it's growing in to name a few. It will flower when it's good and ready to flower. Just remember prune after it finishes flowering and you won't go wrong. Fertilize once a year in the very early spring with a “rose fertilizer” and not a “lawn fertilizer” or apply compost in the early spring.

Fig with Yellow Leaves

Q. I am reaching out to you to see if you could offer some advice on my established fig tree. I noticed that some of the leaves have turned yellow with browning at the end and are drying off. The tree seemed to be healthy up until the last couple of weeks. The fruit seems to be in good shape. 

 A. The fig tree appears to be okay except for a few yellow leaves. The picture you sent shows the yellow leaves in the shade or interior of the tree. That could be normal if the leaves are not getting enough sunlight they will turn yellow and drop. The most important thing is the growth of the tree and fruit production. You haven't mentioned it's growth but the fruit production seems to be good from what I understand, another indicator that the tree is healthy. There doesn't appear to be a problem except the yellow leaves in the shade in the center of the tree. For those reasons I would tell you that there isn't a problem.

I would suggest however that you keep the grass away from the base of the tree two or three feet. Dig out the grass from this area and cover the soil with wood chips. Rock would not be a good idea there. Do not plant annual flowers in that area but you could put a circle of edging around the tree to contain the mulch. I would not plant anything in the mulch area but keep it free of weeds. The fig tree will get plenty of water and fertilizer because of the lawn. 

It will not need anything extra. Make sure that the lawn is not getting so much water that it harms the tree.

How to Grow Roses in the Desert

 Growing roses in the desert is not as hard as one might think. It follows alot of the same principles of growing other mesic plants. 

Landscape Fabric or Deeper Rock Mulch?

 

Q. About a year ago your newspaper column had a clip about stopping annual weeds & it’s in your column in the RJ this past Saturday. I had my yard re-rocked & took your advice over the advice of the landscaper who wanted to put down a screen to stop weeds. I paid extra to have him put down a 3 inch layer of rocks. I believe last year you said 3 inches & this year 4. So, now I have a lot of weeds in all of the rock areas! What happened?

Black plastic mulch under a rock mulch and eventual unsightliness.

A. Great questions and I apologize for any misunderstanding I may have created. I don’t have any pictures to go on so I’m using my imagination. Let me tell you my thoughts about this.

Do you know that the time (and money) spent to control weeds beats out time (and money) spent to control insects or diseaseor both of these combined? It's true in agriculture, too. Weed control is timely and expensive.

Here plastic is applied under rock mulch bordering a lawn. The plastic is suffocating the roots of Italian cypress and causing it to yellow.

There is some research done on the use of thicker rock mulch versus using a landscape fabric (sometimes called a weed barrier and you call it a screen). There are a number of recommendations about what to do when laying down any type of much whether it is rock or wood. The information I see on using both is either from marketing and sales of landscape fabric or from landscaping companies promoting it. 

Landscape fabric starting to poke its head out from under rock mulch in a couple of years.

Using landscape fabric under rock or woodchip mulch looks good in the beginning.

Pro landscape fabrics

The Spruce - How to install landscape fabric

Bob Villa - Landscape Fabric 101

There are some sites that are against its use. This can be from informational sites or landscapers. Its not a "magic bullet" when it comes to controlling landscape weeds.

Con landscape fabrics

Linda Walker-Scott - The Myth of Landscape Fabric

Garden Rant - Is landscape fabric ever not horrible?

Plenty of contradictory information out there and I think the main reason for using landscape fabrics AND mulch is hope. This includes landscapers as well.

Black plastic under rock mulch and planting.

First of all, don’t ever expect total weed control from anything whether it’s by mulch, a weed fabric or both. Wherever water is applied there will be weed growth. The most common places whether there is fabric applied are not is where the drip irrigation is applied. Weed barriers do nothing to prevent bermudagrass, nutgrass and many other weeds from growing. 

Whenever installing mulch, whichever method you use, take the time to kill weeds first before using landscape fabric or not.

Spray marker (paint) is used to mark where weed control spray is applied to a landscape to reduce spraying weeds twice.

Origin of Landscape Fabrics

Weed control barriers had their start in commercial agriculture. It was then adopted to landscapes.

Here black plastic mulch is used as a temporary mulch for weed control and warming the soil early for lettuce production in Kosovo. Straw is used between the beds as a temporary mulch.

The most effective depth for rock to cover a surface is at least 2 inches deep. Nothing is gained by having the rock deeper than four inches. The problem in making a rock mulch two inches deep. evenly, is it takes precision. Higher areas are one inch deep and low spots are three inches deep. The best choice is probably three inch depth but certainly not more than four! That's a waste of money.

Best depth for rock mulch

Hence, landscape fabrics are not recommended for weed control practices in landscape planting beds. 

Non-chemical Weed Control Strategies for Nurseries and Landscapes: Part I

Reason for Justifying Landscape Fabric

A reason for applying landscape fabric is weed control. One reason for applying a mulch is weed control. They are supposed to do the same thing. Why apply two things for the same reason? 

Applying rock mulch is a permanent layer. Landscape fabrics or weed barriers are temporary weed barriers. You are applying a temporary weed control barrier under a permanent layer. Do you see the problem that will arise if the temporary barrier fails? This doesn’t make sense to me. Using two things for the same purpose? And applying something temporary under something permanent?

What to do? 

If you have it under rock or wood mulch then it is there. Nothing you can do about it but it will be a big job if it has to be removed because of unsightliness. Hopefully it is not a solid sheet of plastic but a fabric that allows air and water to plant roots. That's better but it can still be unsightly over time.

Hand weeding. Most, probably about 90% of the weeds that you see at first will be annual. They can be easily removed with some hand labor and a hoe before they flower. Another option (one that I use with rock mulch) is a fire weeder like Red Dragon and propane. Make sure your municipal ordinances allow its use first.

There are weed control chemicals you can use to control weeds around your landscape plants without hurting them. Try applying fusilade weed control products for grass control growing in non grassy landscape plants if bermudagrass is the problem. Look for fusilade (fluazifop-p-butyl) to be listed in the active ingredients on the label. In some cases the product is simply called Fusilade. (I agree its a lousy name to remember). 

Permanent Weed Control

Permanent control of weeds is impossible but you can reduce the amount of time you spend weeding. Persistence. 

1. Never let weeds flower. This makes seed. "One year weeds, seven years of weeding." (old gardening adage). Remove them before that happens.

2. Remove weeds when you first see them. It will begin starving your worst weed problems out and you will see a reduction in your efforts the first months of your efforts! If you do this, the amount of weeding time spent on your property will become less. It will never be nothing, but it will be less.

Bottle Tree, Leaf Drop and Sun Damage

Bottle trees (Brachychiton populneus and locally called Kurrajong) are Australian native trees found in the northern tropical and subtropical climates there. They are classified as “drought deciduous”. Drought deciduous just means they start dropping leaves when the soil gets dry from September through December every year. For B. populneus the swollen roots are thought to store water for dry periods.

The other common Bottle Tree, (Brachychiton rupestis), does this as well and has a trunk with more of the traditional "bottle" shape. Both grow too tall and large for most home landscapes. They can be grown in lawns if not overwatered and you make sure the soil will drain fast. If these trees are watered too often or the soil does not drain well, the roots of the trees can suffocate and the trees die.

Bottle tree with horizontal limbs and thin bark gets sun damage and can drop its leaves if the damage is severe. This tree has thin bark that should be protected from intense sunlight and vandals.

They are thought of as "desert trees" but they aren't. The intense sunlight of the desert can burn their horizontal limbs and, if enough damage is done by the sun, the leaves will drop. 

Use Florel to Eliminate Fruit You Dont Want

Q. I have a 25-year-old fruitless cherry plum tree in my backyard. It is a beautiful tree, and has grown wonderfully through the years, however it has not been fruitless.  Some years have had more fruit than others, but the last few years it has been covered, with tons of fruit, making a real mess and attracting ants and rats. I was told that there is a spray that will stop it from bearing fruit. I found something called Florel, which you apparently spray on with a hose, at the perfect time between mid and full bloom in the spring. Will this work? Will it hurt bees?

This is a cherry plum called 'Sprite' , a Myrobalan plum used for fruit production. The fruit has a very high sugar content but very sour. Some types of Myrobalan plums are used as ornamentals.

A. You did some good investigating. It must be applied when it is flowering. It is safe to use around honeybees and other pollinators that might be present during the flowering time. 

For any of these "fruit eliminator sprays" it is important that the flowers are open so the spray can reach inside the open flowers and cause the ovary to abort. 

This is a fruit eliminator product, Florel, that can be used as a spray to eliminate fruit and seed of plants. The spray will not hurt bees.

Yes, Florel will work. It is best to spray when the flowers are starting to open (20% of the flowers are open) and repeat the spray when the first flowers that open are shedding their petals (80% of the flowers are open). Flowering can take two to three weeks for all of the flowers finish. The first flowers to open are those in the warmest parts of the tree (usually south, west and tops of trees) and the last to open are on the north side and those in the shade. Follow the label directions for mixing the spray with water. It won’t get all the fruit 100% but most of it. 

It is sometimes called flowering plum and it is a fruit tree. It has been selected as an ornamental because of its beauty. In the fruit tree industry it is sometimes used as a rootstock for fruiting plums and peaches and called Myrobalan plum or just plain old Myro. The fruit has wonderful flavor, very tart but full of sugar and makes a wonderful jam or jelly. 

Choosing the Right Vegetable Varieties are Important and Other Tidbits

Q. Can you also guide regarding quality of seeds and plants and recommendation for places where to get them from? Any guidance how I can improve my crop for next season?

A. Use tried and true vegetable varieties that have performed well in desert locations in the past. Make sure your vegetable seed and transplants are in good shape at the outset. Avoid purchasing seed from open locations unprotected from the elements. Dont buy transplants that appear sickly or have a problem. You are not a plant "rescuer" when it comes to problem plants. They wont perform very well. Usually the east side of walls or buildings in full sun give the best protection from late afternoon damage from sun and heat.

I get emails from newcomers to vegetable growing in the desert that try vegetable varieties with marketing claims of "amazing results" from newer varieties. Introduce newer untested varieties in small numbers and notice which do well. 

Some suggested varieties to start with include:

Vegetable Varieties

Asparagus - UC 151

Beets - Detroit Dark Red

Bush Beans - Contender

Broccoli - Packman

Cantalope - Hales Best

Carrots - Chantenay

Cauliflower - Snowball

Cumber - Straight Eight

Eggplant - Thai Long Purple

Garlic - California Early

Hot Pepper - Jalapeno

Kale - Russian Red

Lettuce - Red Sail

Onion - Yellow Granex

Peas - Knight, Cascadia

Sweet Corn - Sweet Rhythm

Sweet Pepper - Red Beauty

Potato - Red Pontiac

Radish - Cherry Belle, French Breakfast

Spinach - Melody

Tomato - Sweet 100, Roma

Watermelon - Bush Sugar Baby

Zucchini - Black Beauty

Windbreaks

Desert climates can be finicky. High and sometimes erratic temperatures can be a problem along with wind and low humidity. Probably the most overlooked climate variable that will improve production and vegetable quality the fastest is controlling the wind. 

Did you know the best production occurs just downwind of a windbreak? They slow wind speed down considerably to a distance of about five times its height. 

Four foot tall chain link fence with PVC slats work well if installed downwind of the growing area's prevailing wind and doesn't require much maintenance or any water! 

Windbreaks made of chainlink and PVC slats slow the wind enough to qualify as a nonliving and waterless windbreak in desert climates.

Grow in Containers

Growing vegetables in containers makes it easier when there is a problem.

Five gallon containers and larger give the plants enough soil volume to hold water in the soil for at least one day during the summer. When you want to increase your growing area try containers first. They are best located on the east side of a wall or building and the container shaded from the hot sun by the raised bed, other plants, or double potted. 

No crop rotation is necessary. Just use the soil from the container for a different crop or cropping season and reuse the soil somewhere else and clean the container, if you use it again, when it gets "worn out", full of diseases like Verticillium or nematodes.

Conks Can Tell You Disease Severity

 Q. A friend has a beautiful, large, old (and productive) fig tree on a property she owns in an older neighborhood. She just observed for the first time large conks. Is there anything that can be done to save the old guy? She loves the tree and is pretty devastated, and is willing to invest to save it if possible. She would definitely have you out to consult if that could be productive. Thank you, and I have been loving your blog for years!

Conks, or bracket fungi, can be diagnostic on trees as to which disease is present and how aggressive it might be.

A. Nice pictures. My presence there wont help her or the tree I think. It is possible this "rotting disease" was brought to your tree on dirty equipment. Your decision to remove the tree is probably necessary at some time. When, I am not sure. If the tree develops weaknesses that could lead to damage or other safety issues, it is time for pruning or removal.

The conks are because of some internal rotting. The color, shape and size of the conks may be an indicator of what disease it has and how aggressive it is. To my knowledge, there is no armillaria root rot locally. To me it looks more like oyster mushroom type of internal wood decay.  Presence of conks low on the tree can mean the rotting is in the roots or crown of the tree. In this case they seem to be higher on the trunk. Try identifying which disease it is by the conk.

Figs regrow very easily from new suckers coming from the base if it has to be cut down. The internal rot CAN be an indicator of a problem and how serious it is. If you an invite an arborist to look at it, of course they will recommend removal. If the tree looks otherwise healthy, then I would knock them off if not wanted and watch the tree for safety weaknesses. It would be a loss to lose fruit but it could be fruiting again in a fairly short time after cutting back.

Make sure any pruning is done using sanitized equipment. Eventually, most likely, the tree will have to be removed. How soon you have to do that depends on how aggressive the disease is. (think cancer, some are more aggressive than others). Maybe removal as soon as a few months to a few years.

Drought Can Substitute for Winter Cold in Asparagus

Q. I am trying to figure out when asparagus goes dormant in the desert. I have been doing some research, but I can’t find information about how to handle the dormancy period in the desert. Any ideas?

This is what you hope will happen in the winter to asparagus. In warmer climates it stays green. Turn off the water to force the plant to go dormant.

A. The usual information about asparagus says it turns brown, or goes dormant, as weather gets cold. That’s true in Michigan or Washington state. Sometimes asparagus grown in warm deserts doesn’t turn brown. It might stay green all winter long.

            Wait for the coldest part of the winter, cut it down like it was brown and turn off the irrigation. In about a month, irrigate and fertilize again to push a new crop of spears. For some plants, drought can sometimes substitute for the dormancy of winter cold.

            Not irrigating can “trick” the plant into “thinking” it just got through its dormant period. In the tropics, we let asparagus “dry out” for a month during the dry season and then start up the irrigation again. Cut it back during the coldest month, turn off the water until the soil dries, put manure, compost or fertilizer on top of the soil and then start watering again. 

When to Harvest Pistachios

Q. When should I harvest pistachio nuts from my five-year-old tree? In October the nuts were yellowish green with a red blush covering them.

The red blush on the nuts means they are close. Harvest after the "meat" has filled the kernel and start to split open.

A. The red blush is an indicator that your harvest season has arrived or perhaps even late. It’s better to look at the number of split nuts on the tree. The general time for harvesting may start as  late as late August or early September and extend through the middle or even end of October.

The nut will start to split when its ready to harvest. Turning red may be a bit late.

            The time to harvest is when the nut inside the husk fills the shell and can be removed. Commercial growers look at the number of split nuts on the tree and whether it might rain or not. Rain will mold pistachio nuts if they are split open. Pistachios are grown in arid or desert parts of the world where, like dates, rain is considered a foe. When harvest time is near nothing beats taking a few nuts off the tree and see if the “meat” is plump and separates easily from the shell.

In some parts of the world there is enough rainfall to grow "wild" pistachios which means they are grown, usually on government land, without supplemental irrigation.

            Drying the nuts off the tree enhances flavor, causes more of the nuts to open and the “meat” to separate further from the shell. If rain is predicted soon, harvest them before they mold on the tree.

Asparagus Growing is Easy with Compost or Manure and Water

Q. My asparagus attempt resulted in five out of 10 crowns dying.  I did as you suggested and dug down as deep as my tiller would dig about 13".  For better drainage I drilled holes another 12" deeper and filled them with gravel. I ordered Jersey Knight asparagus and planted as per their instructions as well.

'Purple Passion' asparagus has purple stems which turn green when cooked. To get long straight spears requires plenty of nutrients, water and cool temps starting to warm up.

Asparagus planting done in late fall or very early spring with amended soil with compost or aged manure. Drip irrigation can be used but watering should follow a similar pattern to watering fruit trees.

A. The usual reason for asparagus dying or growing poorly after planting is because the plants are watered too often, and the crown or roots drown. Asparagus must be planted in soils that don’t hold water. If the soil holds water easily or there is poor drainage then consider planting asparagus crowns just below the surface of the soil and mound the soil eight or 10 inches above it. Mounding the soil provides better drainage in heavier soil.

Asparagus crowns like this one can give you 100% male plants which produce higher yields. Taste is the same.

            Don’t water deep rooted asparagus the same as other annual vegetables. They could be watered with other perennial vegetables such as artichokes or even fruit trees or landscape trees and shrubs! If in doubt, use a soil moisture meter with the tip inserted at about 4 to 6 inches deep in the soil. Never trust a dry soil surface to tell you if the soil where the roots are growing is dry or wet. Water again when the average needle measurements register midway or around “5” on the moisture gauge.

Asparagus can be started from seed but its better if grown from crowns. Seed results in a 50/50 stand of male and female plants. Female plants are not the heavy producers that male plants can be.

            Asparagus grows in the wild near the edges of irrigation ditches in the desert. But not in the ditch. This means they like to get their “toes” occasionally wet but not submerged. These locations are similar where palm and fig trees like to grow. I had good luck growing asparagus between fruit trees when they were young and there is enough light. When fruit trees get older and dense, it is more difficult to grow asparagus because there is less light. Move the crowns to new locations during the winter months where there is moisture and adequate light.

If the winter is not cold enough to kill asparagus tops then cut them back, turn off the water for a month and resume production.

            Adding rock beneath the crowns doesn’t help drainage at all. It’s the same story with sand. To get any kind of soil improvement requires additions of 80 to 90% sand above and below where the plant roots are growing. Research has not looked at gravel but I assume it is the same. But additions of rock above the crowns cause them grow crooked spears. Straight spears require soil above the crowns without rocks.

            In my trials over the years, all varieties of asparagus (12 different varieties) produced spears but the longest and most saleable spears were produced by UC151 hybrids bred by the University of California in Riverside for the hot, dry desert. All the “Jersey” varieties, bred by Rutgers University (New Jersey), didn’t yield as well in the Mojave Desert. You get quality spears with other varieties, but the spears must be harvested earlier than UC151 and this makes them shorter. This holds true for old-fashioned varieties like Martha Washington and most purple types.

            I fertilize asparagus in midwinter with a layer of manure or compost applied once a year and watered in. You can also use a high nitrogen fertilizer, but it will not improve the soil like manure or compost does.

Ideal Time to Plant Anything in the Desert

Q. Is it too late to plant new plants?

Yes, thats my shoe on a soil we will soon plant to vegetables. But not without adding compost at a rate of about 1/3 to 1/2 by volume to that soil.

A. October and most of November are good times to plant in the Eastern Mojave Desert. The ideal time for planting is in the fall and spring. No one argues that but plants are for sale 12 months of the year. Early fall is when I encourage people to plant. Late fall and winter is not the “ideal time” for planting but you can still plant. When planting, always avoid the intensely hot summer months of the desert.

Always Better in the Ground

It is always better to plant in the ground rather than wait for a better time. Just make sure the planting area is suitable for the plant. Plants do not establish their roots in soil as quickly when the soil is cold. One growing season is all that is necessary when staking most new plants.

Know Your Plants Ancestry

If it’s genealogy is the Mediterranean region or arid parts of the world, it most likely performs best with wood chips covering the soil surface rather than rock. Plants originating from the desert Southwest tolerate rock and poor soils better but don’t necessarily grow to their full potential in that type of soil.

Should I use Rock?

Plants that perform best surrounded with rock mulch covering the soil surface are plants that originate from the deserts of the Southwest. If the soil is poor to begin with, covering it with rock will not improve it. 

Be Sure the Soil Drains

All plants perform better with additions of organics like compost mixed into the soil surrounding the roots when its lacking. Some, like cacti and succulents, require less but they all of them grow better with amended soil provided there is good drainage. All plants that originate from deserts prefer soils that drain water. Plants that originate from wetter places, but can handle the heat, are usually more tolerant of wetter soils.

Fungicides Protect Plants, Just Like Insurance

            Do you have insurance? Companies selling insurance are betting you will not have a problem. You, on the other hand, are betting you might. Fungicide use follows the same reasoning. Fungicides, unlike most insecticides and weed killers (herbicides) protect the new growth of plants and keep diseases from starting or spreading. Because the disease doesn’t occur, you may not be convinced it did any good.

            We collectively use the term “fungicide” to describe any pesticide aimed at preventing a disease from fungi, bacteria, virus or mycoplasma like organisms (MPO). Most diseases are caused by fungi but there are a few, like fire blight, which are caused by bacteria and others like Ash yellows or Ash decline caused by MPO’s.

            Desert climates like ours have a low humidity so plant diseases aren’t frequently seen unless we do a poor job choosing plants for the wrong landscape spots, planting, watering, or managing them. Agriculturally Las Vegas is isolated and that also works in our favor. We have far fewer fruit and vegetable diseases here than in agricultural hotspots.

            What can you do to prevent plant diseases? Clean and disinfect tools and equipment. Whether you are doing it or someone else, make sure these tools are clean and sanitized. Make sure supplies you are using are clean. Clean any used pots and containers with bleach and let them air dry for 24 hours before reusing them. Don’t compost diseased plant parts or reuse them. Instead, securely wrap them in plastic and put them in the garbage. If the disease is known to be virulent such as fireblight, get diseased plant parts off the property as soon as possible. Thin out dense plants to improve air movement through their canopies. Whether you are growing tomatoes, fruit trees or shrubs, when they are dense they need to be thinned by selective pruning and growing vigorously to prevent diseases.

Some diseases (biotic, coming from pathogens) I have found in the desert include:

Fireblight – Asian pears, European peers and apples and including many ornamental plants in the rose family including Pyracantha

Fireblight on Asian pear

Root rot and collar rot – many different fruit trees and ornamental trees and vegetables

Chokes the tree or plant at or beneath the soil because the soil is cold or too wet, poor drainage or all three

Ash decline – most ash trees

Limbs dying in established ash trees

Other suspected plant diseases probably encountered are: oleander leaf scorch, Pierces disease on grape, Verticillium wilt on vegetables and, Fusarium wilt on palms and vegetables, white rot on onion and garlic, summer patch on tall fescue, to name a few.

Always use sanitized equipment and sterile soil and containers when possible. By the way, my favorite sanitizer is alcohol after everything has been cleaned with soap and water.

Where to Get Sabadilla for Insect Control

 Q. I have been looking for replacement of my sabadilla dust that is just running out now. I have been unable to find it.

Pyrethrum (Chyrsanthemum) grown on a farm in Kenya and sold to a European company who makes natural pesticides (pyrethrum powder).

A. I did an extensive search for sabadilla as an insecticide. It is now sold mostly as a homeopathic treatment for sinus congestion. As you know it has been around for decades. I remember it as an "organic" pest control measure before the organic movement began. It is made from the seeds of the sabadilla plant (Schoenocaulon officinale). Others in that old group of plants that served as sources of insecticides include rotenone (aka, derris, from seeds and stems of several legumes) and pyrethrum (extracted from chysanthemum flowers). 

Pyrethrum is now being synthesized industrially (called pyrethroids) and has morphed into manufactured insecticides like permethrin, resmethrin, and others. Pyrethrin morphs are used mostly by the interior pest control industry to control termites, ants and mosquitoes. Some claim the morphs were over profits and others claim it was for effectiveness and the targeting of specific insect pests.

Sabadilla is now sold mostly as a homeopathic medicine for allergy symptoms. 

It has come full circle and is sold for outside pest control use only by one supplier (to my knowledge) and the formulation has changed over the years from a dust (D) to the more popular wettable powder formulation (WP). https://www.mgk.com/product/veratran-d/

Nopal Cactus (Copena varieties from the Sonoran Desert) Grown for Food Elsewhere

Q. I am a special education teacher and gardener in Sonoma County, California, and I've been searching for Copena V1 or F1 cacti to cultivate here in Santa Rosa. I have been doing some research and learned from Everardo Zamora at USON that you had acquired some specimens of this variety some years ago. I would like to pick your brain about their cultivation and potential as an easy-to-grow food source in my area.

Copena flower and fruit production in the Mojave Desert at UNR Research and Demonstration Orchard in North Las Vegas

Bob Morris (Xtremehorticulture) and Everardo Zamora (USON) talking about Copena nopal cacti growth and production in the Mojave Desert

A. 

Bird damage to copena nopal cacti fruit (tuna).

Flower from Copena nopal cactus.

Winter freeze damage to Copena nopal cacti.

Cochineal scale damage to Copena cacti pads

A. Nice to hear of your interest in the Copena nopal cactus. I consider Everardo a good friend. Copena cacti are very easy to grow but it's just too cold during the winter in Las Vegas.  They will have freeze damage a little bit below freezing temperatures (maybe about 30F). Regardless, they produced high quality fruit and pads to use as fresh vegetables, fruit and for livestock feed even after a freeze event. Freeze damage was our biggest problem in the eastern Mojave Desert. These are high quality eating cacti (nopalitos and tuna) from the Sonoran desert and developed by the University of Mexico.

The biggest problems I experienced with them are:

• Cold (freezing) damage from winters colder than the Sonoran Desert
• Bird damage because they are so sweet (may require netting)
• Rabbit damage during the winter because they are spineless and not much out there for rabbits to eat in the winter (may require rabbit protection)
• Constant spraying with streams of water to keep the cochineal scale at bay (no commercial insecticides were applied)
• Controlling leaf-footed plant bugs (a growing problem in the Mojave Desert)

I irrigated them about every 3 weeks with a bubbler in basin type of irrigation to push new growth for harvesting and fertilized them for production once a year in the spring. Plants were established by pads donated from USON. They start flowering in their second or third year after planting.

Narcissus for the Mojave Desert

Q. I accidentally cultivated up a bunch of daffodil bulbs. When is the best time to replant them in Las Vegas? They show no signs of green.

A. If these daffodils have been in the ground in your landscape for several years then chances are you can just replant them and they will continue to flower next spring and probably every year thereafter. If they did not flower last year, or they flowered erratically (some years you got beautiful displays and others were disappointing), then you should read the rest of this information. 

To get consistent flowering year after year, you may need to put them in the refrigerator through the rest of the winter to get consistent flowering. You can also opt to buy "prechilled bulbs". But be forewarned: this refrigerator treatment may need to be done each year to get reliable blooming. This is also true of tulips and some other very popular cold climate bulbs. 

Replant them on the east side of the house so that they get morning sun but are protected from late afternoon heat. Amend the soil with about 20 to 30% compost when planting. Never cover them with rock. Woodchips are okay but not rock. They will not grow well in total shade or in hot bright locations. They will also not grow well in rock.

It takes the right variety of daffodil for it to bloom every year here. Local nurseries rely on their suppliers to sell them the right daffodils for this climate. Las Vegas, climate-wise, is halfway between a tropical climate (think Hawaii) and a cold climate (think Minnesota). Las Vegas lies in the northern belt of climates termed loosely “semitropical”: Cold winters to the north and warm winters to the south.  It lies in the transition zone between the two. Did you see flowers from them before? If you did, then just replant them.

There is never any advertising on my blog. It runs off of donations so here is stuff I found helpful.

Here is another article about this topic.

Here is a source for daffodils that will do well in warm climates. Just enter your zip code.

A second source of bulbs for warm climates.

A third source of bulbs for warm climates.

Desert Horticulture Podcast: When to Prune Flowering Trees and Shrubs

 It's very simple. Prune flowering trees and shrubs after they finish flowering. Now learn why and how to prune these plants in the desert.

Texas Ranger on the right was pruned with a hedge shears in June.

Looking for Sabadilla?

One reader looking for sabadilla and having no luck finding it. Sabadilla was very popular maybe 40 or 50 years ago as a "natural" pest control product. You can read more about other natural products including sabadilla by clicking here. Since that time other products (insecticidal soaps, Neem, spinosad products, pyrethrum, Bt and others) have grown in popularity. At one time sabadilla could not be found for sale in the US. It is back and growing in popularity. 

 It might have some potential against the leaf footed plant bug since it has been very effective in the past on squash bugs. But like any label for an insecticide, the crop you are spraying MUST be on the label in some way (even if it says vegetables or fruit trees!) and preferably the insect you are trying to kill as well.

Leaf footed plant bug

 

Squash bug on the underside of a squash leaf. About the same size as the leaf footed plant bug.

Q. I have a small amount of sabadilla dust leftover from about 30 years ago. It was the only thing I found that was very effective on squash bugs. I am having trouble finding it. Do you know where I can get more?

A. Sabadilla was made from the ground seeds of the sabadilla plant (S. officinalle). Sabadilla was not available in the US for a couple of decades but it is back. I remember it from my past but I had never used it. Now it is sold mostly for homeopathic treatments for allergies and runny nose. 

I did find one source (I think it might be the only one) online here available from MGK as a "USDA organic" insecticide. It is now a wettable powder (WP) and not a dust (D) anymore (dusts for the most part went by-by years ago and now you can find a few available to homeowners) so it must be mixed with water and applied as a suspension (some sort of agitation of the WP solution is required to apply it evenly). Suspension can sometimes be achieved if you stop and shake a hand sprayer regularly (keep the solution in motion) when you apply it.

Remember, "dose makes the poison" so anything considered "natural" or organic can be lethal if used the wrong way. I figure that if something can kill bugs, then it can kill me. That's true of anything including soapy water and table salt! So use any so-called "natural" or organic product with the same caution you would use with anything that can kill. Wash your clothes and take a shower right after you apply it. That is true of your dust product as well. And wear gloves at least! Always apply insecticides on a still, warm day.

Desert Horticulture Podcast: Confused About Pomegranates?

 There are over 600 varieties of pomegranates with all sorts of flavors and colors that make this a unique and hardy fruit tree for desert climates. 

Yellow pomegranate near northern Tajikistan

Protecting Orange Fruit from Freezing Weather

Q. My oranges haven’t ripened on my two-year-old tree. Some are green and others yellowish with very hard skin and last year’s fruit wasn’t very sweet or soft.  Should I cover them tonight? It will be freezing.

Its possible to get oranges in Las Vegas if the weather cooperates, you have a warm microclimate in your landscape and we dont get a hard freeze.

A. The fruit of many oranges attached to the tree are damaged at temperatures of 30°F or a few degrees lower.  The type or variety of sweet orange is highly variable to freezing temperatures. If you think winter temperatures will drop low enough for damage, then throw a sheet or blanket over the tree to protect it from cold and wind.

Go outside at night and look at the sky. Clear skies are more likely to contribute to lower temperatures than cloudy skies. If there is wind combined with freezing temperatures, fruit damage is worse.

Even though these oranges are ripe they are green. Thats because they are in the Philippines, a tropical country.

Your oranges may not be ripe yet. Ripeness depends on the variety and when it’s supposed to be harvested. Cold weather will get them to turn orange as they ripen. Oranges grown in tropical climates never turn orange when they are ripe. Consumers know this and their green color is acceptable. If they are ripe enough, put them in a paper bag with a few ripe bananas for a day and they will soon turn orange.

My guess from their color is they should stay on the tree longer. If they are sweet, they may handle some temperatures down to about 28F or so. Citrus grown in US commercially are found in in Yuma, Arizona, Rio Grande Valley in Texas, mid to south Florida and southern California. These places seldom freeze.

            Ripe fruit handles temperatures a couple of degrees lower than unripe fruit because of their natural anti-freeze; higher sugar content. The sweeter the orange, lower temperatures by a few degrees are needed to freeze them. If you want to measure the sugar content, follow my blog and type in the word “refractometer” in the search line.

            Our desert climate creates winter temperatures too low for growing and producing citrus. You might have a couple of warm winters in a row followed by low winter temperatures that may wipe out the citrus.

Will citrus grow in Las Vegas? Some years, depending on where they are planted and your choice in citrus. Will they produce fruit here? Sometimes, depending on when they flower and the temperatures just before and after flowering. 

Talk to your neighbors and look around your neighborhood. If your neighbors were lucky at growing oranges, you might have the same luck. Be suspicious of neighborhoods that have no citrus growing in them at all. There might be a weather and climate related reason for that or you might be the pioneer who starts something.

Pay attention to the type or variety of orange you have. You call yours an “orange”. This orange has a name or variety besides just “orange”. These different varieties of oranges flower and are harvested at different times. Some perform better here than others.

The “University of Arizona” published a fact sheet that you can retrieve online called, “Low Desert Citrus Varieties”. If this link is broken, use your favorite search engine and type in these words in quotations and look at the last two pages. This fact sheet tells you the harvest time for different varieties of citrus. Avoid varieties that are ready to harvest in the middle of December or later in the season.

 

 

Tree-Like Photinia Damage after Landscape Conversion

Q. We did a landscape conversion, removed the lawn and now our tree-sized specimen, multi-trunked photinia, is declining. The trunk has cracks, it’s gray and looks ugly. We bought Tree Secret fertilizer and applied water per the directions and it seems to be better. We added more lines around the basin to increase the amount of water and have mulched around the tree. When is the right time to trim it?

Tree-like photinia after landscape conversion

Grey and cracked trunk of photinia due to sunburn and possibly borer damage.

A. The photos you sent regarding the photinia were eye opening. I will post them on my blog as well, Xtremehorticulture of the Desert. These cracks in the trunk and gray color are from intense desert sunlight shining on the tender trunk. This might also include borer damage under that grey, cracked area of the trunk. The grey cracked bark is covering the dead side of the trunk so go ahead and remove the bark and see.

This is sun damage (advanced sunburn) to the trunk of a locust tree and the tree is surrounded by rock. Very similar to the damage on your photinia trunk.

In my opinion, you would have improved the plant by just applying water to a larger area under the canopy and not an expensive fertilizer. Applying a quality compost to that area gives the same benefit as any well-balanced fertilizer. In fact, a well-balanced fertilizer is formulated to substitute for what a compost does naturally. There are no “secret ingredients” when growing plants, just marketing and “time savers” similar to “Hamburger Helper” used in some kitchens.

This intense sunlight shining on a tender trunk results in sunburn, then death to the part of trunk that faces this intense sunlight. This damage is oftentimes followed by attacks by boring insects starting the same year as the damage. Sunburn is known to attract boring insects which has been the consequence of sunburned plants over and over for eons. Desert plants like palo verde and mesquite do the same thing if their tender trunks are exposed like your photinia.

What does photinia look like in a milder climate?

There are two problems going on. Photinia, native to Japan, is not a desert plant and its trunk sunburns easily when exposed to intense sunlight. The other is the landscape microclimate, i.e.,  where it is planted in the yard.

What to do? Obviously, this plant can’t be moved to a cooler microclimate in the yard. And it appears to have done well in that spot before the landscape conversion. I would expand the area irrigated to as much of the area under its canopy as possible. Ideally, irrigating the entire area under the canopy is best. 

Secondly, root prune the plant to the edge of its canopy by slicing into the wet soil at the canopy edge with a sharp shovel. The photinia has this fall, winter and spring to grow new roots just inside its canopy before it gets hot again. These new roots will find the water.

The direct harsh sunlight caused significant damage to the exposed trunk. Microclimate. I think exposing the tender trunks to direct sunlight may have burned them. Not much you can do that looks nice. You could paint the trunks with a very light coat of paint (light colored latex diluted half and half with water) but that might look kind of weird considering. If there are suckers that are growing from that area then leave enough to shade the trunk until it heals. Plant other plants in that area to shade the trunk. 

The trunk will heal in a year or two if this problem hasn’t already strangled the trunks.  You might consider planting something tolerant of the heat to shade the trunk and give it a chance to heal. You might consider lightly draping some burlap between the sun and the trunk to shade it until it can provide its own shade. But whatever shade you can create to keep the sun from damaging the trunk will help.