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Tuesday, June 18, 2019

Uses of Gibberellic Acid

 I put this on my blog in response to a question I recently received

Uses of Gibberellic Acid
Robert L. Morris
March 10, 2009

Gibberellic acid (also called Gibberellin A3, GA, and (GA3) is a hormone found in plants. Gibberellic acid is a very potent hormone whose natural occurrence in plants controls their development. Gibberellic acid promotes growth and elongation of cells. It affects decomposition of plants and helps plants grow if used in small amounts, but eventually plants develop tolerance for it. Gibberellic acid stimulates the cells of germinating seeds. Since GA regulates growth, applications of very low concentrations can have a profound effect while too much will have the opposite effect. It is usually used in concentrations between 0.01-10mg/L.

Gibberellins have a number of effects on plant development including rapid stem and root growth and increase seed germination rate.

Gibberellins are used in agriculture for various purposes. GA-3 is sprayed on seedless grapes to increase grape size and yield, and it is used on navel oranges, lemons, blueberries, sweet and tart cherries, artichokes and other crops to decrease or increase fruit set, delay rind aging, etc. These effects are highly dependent on concentration and stage of plant growth. GA is used to trigger flowering of sweet potatoes in breeding programs, to help tomatoes set fruit at high temperatures in the tropics, overcomes the need for chilling or long days to trigger flowering, and so is used in the tropics for breeding.

Developing seeds are active sites of containing GA and studies have found increases in GA levels in seeds during germination. The germination of old seeds has been improved with use of GA. Applied GA-3 may trigger dormant seed germination, in many cases overcoming the need for special or prolonged dormancy-breaking conditions such as cold treatment, light, after-ripening, etc.
  1. Overcoming dormancy. Treatment with high concentrations of GA is effective in overcoming dormancy and causing rapid germination of seed.
  1. Premature flowering. If a plant is sufficiently developed, premature flowering may be induced by direct application of GA to young plants.
  1. Increased fruit set. When there is difficulty with fruit set because of incomplete pollination, GA may be effectively used to increase fruit set. The resulting fruit maybe partially or entirely seedless. GA has increased the total yield in greenhouse tomato crops both as a result of increased fruit set and more rapid growth of the fruit.
  1. Hybridizing. Pollination within self-incompatible clones and between closely related species may sometimes be forced by the application of GA and cytokinin to the blooms at the time of hand pollination.
  1. Increased growth. GA applied near the terminal bud of trees may increase the rate of growth by stimulating more or less constant growth during the season.
  1. Frost protection. Spraying fruit trees at full-blossom or when the blossoms begin to wither can offset the detrimental effects of frost.
  1. Root formation. GA inhibits the formation of roots in cuttings.
ml (cup)
2400 (10 1/2)
Early flowering
600 (2 1/2)
Early flowering
160 (2/3)
Blossom set
60 (1/4)
Seed germination
1% paste
5 ml (1 tsp.) lanolin
Growth promoter
Table 1. Preparation of bloom or sizing sprays of gibberellic acid for use on various table grape varieties

Gibberellic acid is sometimes used in laboratory and greenhouse settings to stimulate germination in seeds that would otherwise remain dormant. It is also widely used in the grape-growing industry as a hormone to induce the production of larger bundles and bigger grapes, especially Thompson seedless grapes. In the Okanagan and Creston Valleys of Canada it is used in the cherry industry as a growth regulator.

Effects of Gibberellic Acid

Although GA is not listed as a "poison", the following precautions should be observed: Flush with water any GA that may get into the eye. Avoid skin contact if possible. If skin contact is suspected, wash with soap and water. Do not re-enter an area after spraying until the GA spray is fully dry. Avoid ingestion of GA. The powder may be dissolved as specified below to give the desired concentration.

Thinning and Increasing the Size of Table Grapes

In varieties like Thompson Seedless, Flame Seedless, Perlette and a few other varieties (seedless grapes primarily) GA3 (gibberellic acid) is used for either thinning out the number of flowers which set fruit, a bloom thinning spray, or for increasing the size of the berries (referred to as a sizing spray which is applied about one week following bloom). 
In some varieties both a bloom spray and one or two sizing sprays are generally applied. Not all varieties respond to bloom sprays for thinning. These varieties may use a gibberellin spray only for increasing the size of the berry. Grapes which produce seeds are generally larger than seedless grapes because seeds produce natural gibberellins which increase the size of the berries.
One must be extremely careful when using GA3 on grapes. Each variety has a different tolerance level and one should not ‘experiment” or use more of the material than is recommended for any given variety.
The gibberellin produced for commercial use in grapes is manufactured by Abbott Laboratories, Merck, and Agtrol. It is produced in both a powder formulation and a liquid formulation. For most home owners, the 4% liquid formulation (containing 1.0 gram/fluid ounce of formulated product) is the easiest to use. Before applying gibberellin to your vines, refer to the gibberellin product label and the variety write-up for levels which each variety will tolerate. Do not exceed the recommended dosages. Higher than recommended levels can severely injure the plant. Do not apply gibberellic acid to grape varieties not listed on the product label.
The spraying guide put out by the companies for the use of 4% liquid on grapes refers to actual grams of gibberellic acid applied in the finished spray per acre. Conversion for only a few grapevines is often difficult; so, refer to Table I below in which the values have been converted to parts per million (ppm) in a one gallon water solution. One gallon of solution is enough to treat two mature grapevines.
The rate of gibberellin used increases as the season progresses. Bloom sprays are generally much lower than sizing sprays which are applied about one week later.

J. L. Hudson Seeds website. http://www.jlhudsonseeds.net/GibberellicAcid.htm
Norton, Maxwell. 2007. Presentation at the University of Nevada Cooperative Extension Orchard Workshop.
Riley, John M. Gibberellic Acid for Fruit Set and Seed Germination. 1987 CRFG Journal (vol. 19, pp. 10-12). And can be found at http://www.crfg.org/tidbits/gibberellic.html
Wikipedia. Gibberellic Acid. Found at http://en.wikipedia.org/wiki/Gibberellic_acid

Monday, June 10, 2019

Leaf Color in African Sumac Speaks Volumes

Differences in trees can be because of their genetics and how they were propagated in the nursery, differences in soil in very small areas and management.

Q. We had 3 African sumac trees planted in our backyard 1½ years ago. We treated them the same during this time but the tree the farthest away has large dark green, healthy leaves and the other 2 trees have lighter color leaves and they are curled. 

A. African sumac is propagated from seed so there is a lot of variation among trees. They also come in male and female trees so let’s remember that as well.
Seeing seed pods in African sumac is a good indicator the tree is female.

            Lighter leaf color can mean the trees are not getting enough nitrogen fertilizer, they are watered too frequently, or the soil does not drain water quickly enough. Because these trees were not planted by you, it’s not known if the soil where these trees are growing drains water similarly or not.
            Let’s tackle the fertilizer issue first. Apply a high nitrogen fertilizer in the basin of the trees just before an irrigation. Let the irrigation water transport this high nitrogen fertilizer to tree roots. If nitrogen fertilizer is the culprit, you should see a change in the leaf color before one week.
Moisture sensors like this inexpensive type used for houseplants can tell you the approximate time to water. Push the probe into loose soil in several places to get a rough idea when the soil is wet or dry.

            Inexpensive soil moisture meters, such as they use for house plants, can give you a rough approximation if the soil is wet or dry and when to irrigate again. Water these trees only when the soil is beginning to dry, never while the soil is still wet. If trees are watered too soon and the soil is still wet, leaves can discolor and become yellow rather than dark green. But the differences in leaf density between the trees indicate a difference in the amount of water they are receiving.

Leaf Drop on Apricot Reasons Why

Leaf drop on any tree can happen if the flow of water from roots to the top is interrupted.

Q. We have a five-year-old apricot tree. Previously, it’s always seemed happy but this year it leafed out beautifully, then it started dropping its leaves. Apricots are still on the tree but not developed yet. Then this week ½ of the branches on one side are leafless.
Another angle of the same tree.

A. Pictures were sent to me of this tree so let me explain what I saw. The apricot tree is 6 to 8 feet tall with a similar spread but leaning strongly toward the light but away from some taller shrubs on one side. Leaves are on the ground and have dropped from the side away from the light. The week it dropped its leaves was a hot week and then it got cool again.
Apricot sap dripping from limbs or the trunk can be a sign of borers particularly if you see it when it gets hot.

Trees drop their leaves because they are not getting enough water. They also drop leaves if it’s too dark, but I think in this case it’s a water issue. A lack of water can be from not enough water applied to the soil under the tree, borer damage in the trunk or several large limbs or a disease problem.
Sap dripping from the trunk can indicate wet soils. Add lots of water and then hold off watering until the soil has begun drying.

            I’m going to rule out the disease possibility because it is highly unlikely in the desert. Borer damage is a possibility except the leaves are dropping at the wrong time of the year and from half the tree instead of a branch. Borers cause leaf drop during the heat of the summer, June or July, frequently affecting an isolated branch or two. So, let’s rule out borer damage.
Wood chip mulch applied several inches think is good for fruit trees planted in desert soils but keep the wood chips a foot from the trunk for the first few years to prevent collar rot. Collar rot on fruit trees looks alot like drought.

            It is possible this tree had gotten larger and was not getting enough water. Along with a shortage of water, the distribution was not over a large enough area under the canopy to satisfy its roots. As trees get larger, they require more water distributed to a larger area under the canopy.
            To test this idea, use an inexpensive sprinkler on the end of a hose, connected to a mechanical timer at the hose bib or faucet. Put the sprinkler about 2 feet from the trunk of the tree and turn on the mechanical timer for two hours so it wets the soil deeply in an area about 5 feet in diameter. Do the same thing to the other side of the tree. Do this twice a week for the next two weeks and let’s see if the tree responds.
            If I’m right, you will see new growth coming from the limbs that are bare and where there are leaves, you will see new growth. If this is the case, increase the number and size of the emitters. Place one drip emitter scattered about every 2 feet under the canopy of the tree. The water should penetrate the soil about 18 inches deep after an irrigation.

Magnolias Need Special Locations and Management

Q. I have two dwarf magnolia trees in my courtyard in front of the house. They started dropping leaves and they’re kind of scarecrow looking. What do I do?
The Mojave Desert is not the easiest place to grow magnolias. Magnolias, Southern Magnolias in particular, will have difficulty growing in a desert climate.

A. Let’s get something out of the way early. This is not magnolia country so they will require extra care and attention here. I hate to sound like a broken record, but it is either water or soil improvement or both.
            Is it planted in rock? That’s a mistake if they are. These are not desert plants so they will not like rock. The soil around them should be covered with a 4-inch layer of woodchips instead.
Find the perfect spot, like planted in a lawn, and they may flourish for a few years. But don't plant them in a desert landscape.

How many emitters do they have? They will need at least four if they are four or five feet tall. These will be placed in a square pattern about 18 inches from the trunk. This will be enough until they get about 10 feet tall and then you will probably have to bump it up to about six or eight emitters spaced evenly under the tree canopy.
            Making sure these trees get more water will stimulate more leaf development and a denser canopy. The water should be on long enough for it to drain to about 18-24 inches deep after each watering. Use a steel rod like a 3-foot long rebar to judge the depth of irrigation.

Asparagus Planting Among Trees

Q. I put in a lot of effort into planting asparagus. I have a large planted area but no asparagus! I planted Mary Washington this year and many times in the past, but I have had no luck. Are the trees nearby this area competing with them too much?   
Asparagus trials in 2008. About 15 varieties of asparagus were trialed in the Mojave Desert and evaluated by chefs for quality. All 15 performed well but those bred for the hot desert could be harvested for a longer period of time.

A. There is a lot to cover regarding asparagus growing here. First, there is no problem planting asparagus among trees if there is room. I will post a primer on growing asparagus in the Mojave Desert in here.

Make Sure There is Room for It

Asparagus gets 5 feet tall after harvesting the spears so make sure it has room to grow to that height. I have had asparagus planted among fruit trees, as well as alone in rows, since 1996. I planted asparagus in 2019 and they are coming up nicely. This is a great climate for asparagus if it’s planted and managed correctly.
Sometimes you will see advice to "snap" the spears off instead of cutting them. I tired it and don't like it. The remaining stubs above ground interferes with operations. I prefer to cut them about one inch below ground with a sharp knife or asparagus knife.

Just make sure the asparagus gets at least 8 hours of sunlight.

Variety Trials

            I have grown about 15 varieties of asparagus for comparison purposes in our Mojave Desert climate. They have all done well but there are some differences among the varieties. Stay away from heirloom varieties such as Mary Washington because they don’t produce enough spears in any climate. There is nothing remarkable about them.
I trialed a purple variety called Purple Passion years back and liked it. The spears were sweeter but the variety didnt produce as many spears as UC157. Choose improved varieties over the old standbys like Mary Washington. I prefer the UC varieties over Rutgers Jersey line.

            Expect an asparagus bed to last about 20 – 25 years if managed correctly. They do well with drip irrigation. I would use drip tubing with emitters spaced about 12 inches apart or plant them in containers for small spaces. In rows using drip tubing, plant in a triangular pattern so that crowns are 12 to 18 inches apart on either side.
Asparagus grows well with drip irrigation. Make sure you find a balance between soil moisture and drainage. If the soil is too wet, the roots will rot. If the soil is too dry, they don't produce well.

Asparagus Loves Manure or Compost Applications

            Asparagus loves rich soil and water but they also like their roots and crowns to “breathe”. Mix with desert soil an equal volume of rich compost at the time of planting about 12 inches deep. Buy two or three-year-old, all-male crowns and plant them 8 to 10 inches deep. Make sure the soil in the asparagus bed is free of any rocks or they will produce crooked spears.
Asparagus spear emergence in early spring after a rich compost application.

Asparagus Must Have Water Drainage

            The soil must drain water easily in a few hours after an irrigation. Irrigate thoroughly after planting but don’t irrigate again until the soil is slightly moist at 6 inches deep. If you’re not sure about when and how much to irrigate, follow my blog, Xtremehorticulture of the Desert, my YouTube video or podcast on how to irrigate. If watered too often, asparagus roots and crowns will suffocate and rot.

Differences in Varieties

            Plant ‘UC 157’ developed by the University of California for the hot desert and plant them from mid-January to early February. Stay away from planting by seed unless you are an experienced gardener. If you want some variation in spear colors, mix in a variety called ‘Purple Passion’ but keep in mind they don’t produce as many spears as UC 157, but they are sweeter to the taste.
Abnormalities do occur like fasciation but they are rare.

Don't Forget to Fertilize

            Each year, before the beginning of the growing season just after the Christmas holidays, apply about 1 inch of rich compost on top of the soil above the crowns and water it in. If the soil has plenty of organics in it already, then use a mineral fertilizer such as 16 – 16 – 16 in early spring.

Wednesday, May 22, 2019

They're Here!!!

Q. Do you know what these bugs are? They don't seem friendly to me.
Leaffooted plant bug seen now on pomegranate, one of their favorites.
A. They are out there now and multiplying fast. Immature of the leaf footed plant bug. A very nasty bug and will feed and multiply on lots of stuff in your fruit trees, nut trees, vegetables and herbs. If you look in there you will see the Mom protecting them from predators.

Leaf footed plant bug adults and advanced juveniles on citrus.

Vacuum with a cordless vacuum cleaner when young like this. If you don't mind pesticides then try pyrethrins and synthetic pyrethrins. If that doesnt work then carbaryl (Sevin) insecticide but it is hard on honeybees so spray at dusk when the bees have returned to their hive because they cant navigate without sunlight.

Leaffooted plant bug later in the year on pomegranate.
Watch out for them on pistachio, almond, tomatoes, and other vegetables, fruit and herbs.

Tuesday, May 21, 2019

Not All Cacti Can Handle the Mojave Desert

Q. I have a cactus garden that faces west. Every summer I hang sheets on a clothesline to shade them so these cacti dont burn from the direct westerly sun and heat. The sheets get stuck in the cactus when the wind blows and pulls the small ones out of the ground. If I don't protect the cactus this year, will they die?
Some cacti like barrel cactus can handle the Mojave Desert environment with no problems as long as you don't water them too often. Photo taken at Las Vegas Springs Preserve.

A. It depends on the cactus and where it comes from. Many people don’t realize that not all cacti require the same type of environment. They are as individualistic as we are.
Watering a Joshua tree too often will kill it. It is a Yucca.

            Cacti are found in a variety of climates, from our harsh desert Southwest conditions, to shade-loving cacti to drought tolerant cacti that survive on moisture from ocean fogs. For this reason, some cacti may thrive in your Western exposure while others need protection.
This is Yucca pendula or soft Yucca and is native to the southeastern United States. It cannot handle intense sunlight so it should be planted in an area protected from strong sunlight in the afternoon.

             You should know by now which cacti are struggling and which are not. Yellowing or turning white on the west sides of these cacti is sunburn. Move these cacti to new locations with filtered light or an eastern exposure. They will recover. Leave the ones which seem to handle the intense sunlight, alone.
Watering a cactus too often or fertilizing it too frequently can cause it to grow faster than it can support itself.

            Learn their common and scientific names and where they come from. Sometimes the presence of a covering of dense spines or “fur” can provide a clue about their sensitivity to direct sunlight and their need for protection.

Growing New Cactus from Cactus Pads

Q. I am growing new cacti from pads cut from the mother plant. You recommended I amend my soil with either compost or manure before planting the pads. I used a local planting soil which was cheap but not a good decision, I discovered. Can I amend this soil and “fix” it?  
When planting cactus pads, make sure pads are planted north – south so that one side of the pad receives morning sun and the other side of the pad receives afternoon sun. Add manure or compost to the soil. Don't water too often. Use a soil moisture sensor like the one pictured to gauge when to water again.

A. You probably can. However, the soil should not be “fluffy” but firm after it’s been watered. If it’s “fluffy”, the cactus will fall over when it gets taller. It will also fall over, or possibly die, if watered too often, watered frequently with small amounts of water, or if water is applied only around its base. Use native desert soil whenever possible, mix in a small amount of manure and build a three-foot basin around the plant for containing enough water applied to it. Water it every three or four weeks in the summer, filling the basin to its brim.
The area around the pads can have a basin built to keep the water from getting away. Monitor the soil moisture to know when to irrigate again.

            Make sure all cuts have healed before planting the pad or it can become infected and rotten. To be done on the safe side, apply a copper fungicide like Bordeaux to the bottom fourth of the pad before planting. This helps keep wounds from rotting when it first get started.
If laid flat the pads will curl over night. Stack them vertically until they are used.

            Plant the entire pad so its flat surfaces are facing east and west and one third of it extends below the soil. Water the entire basin and let it soak into the soil 12 inches deep. The roots will form from the pad using stored water taken from them.

Take Plants Out Of Containers When Planting

Q. I see landscapers putting new plants in the ground without removing the black plastic pots.  I see these same plants thriving and doing a whole lot better than some of my own which I have planted in amended soil and surrounded with mulch. And that really ticks me off.

A. Sometimes it doesn't seem fair. You do everything right and your hard work doesn't seem to pay off. At least in the short run. Plants will grow in water if it has air bubbling through it and fertilizer available. That doesn’t mean it’s a healthy environment for their long-term survival.
            Soils used to produce plants in containers are inexpensive to make, lightweight so they are easy to carry and transport and drain water quickly. Plants growing in containers must be watered often and “fed” with regular applications of fertilizer. Container root environments encourage fast plant growth but are not intended for the long haul.
            Recently, I saw one-year old Western Redbuds in containers for sale at a local box store. The soil was sawmill waste plus fertilizer mixed in it and they were four feet tall! However, the trees were poorly rooted in the container, they had trouble staying upright, but they were big for one-year old trees!
            Plants in containers will continue to do well after planting in the ground, container and all. This is because the containers, together with the plant roots, are surrounded by cool soil and no longer punished by intense sunlight and high temperatures. After planting, plant roots grow through the bottom of the container and into the surrounding soil in just a couple months. The top of the plant grows quickly but its roots are surrounded by the plastic container, impeding its establishment.
            Vigorous plants survive through this ordeal, but more delicate ones will struggle and probably not. Landscapers are long gone by the time plants begin struggling. Some become weak and struggle after a couple of years growing with this plastic container surrounding its roots.
            Plants always perform better over the long term if planted into the soil and cared for properly. Some may struggle for the first few years. But most plants perform best if our soil is amended at the time of planting, giving them a good start. Stake larger plants the first year and water so that at least half the roots under the canopy are getting water as they continue to grow.
            Apply enough water so it infiltrates into the soil 1 foot deep for small plants and 2 feet deep for small and medium sized trees. Wood chips on the surface of the soil improve it so that the majority of its “feeder roots” are growing in the top few inches which they love but takes a season or two before they “catch”.

Desert Landscapes Require Water

Q. I'm transitioning to a landscape with only Mojave Desert native plants.  Cacti, yucca, agave were planted early last spring and are doing well. Will this type of landscaping ever be free from irrigation like they are in the open desert?

This is the Mojave Desert, unglorified, about 20 miles north of Kingman, Arizona. Notice the size of the plants. Notice their density. Notice what type of plants they are. This type of landscape requires no extra water. Is this really the type of desert landscape you want?

A. That’s a tricky question because it assumes you’d be happy with this type of natural landscape. There is not much shade in the open desert. If you prefer larger plants to create shade in your landscape, then having additional plants might be worth the extra water. If you like the open desert and retreating into your house for shade then yes, you can probably achieve a landscape without extra water. It might not be very pretty, but you can do it. If not, then it will take extra water to get what you want.
With some wisely placed irrigation water using a bubbler and basin, some compost at planting time, some wood chip mulch and annual applications of fertilizer and iron you can grow Crape Myrtle like this one at our research site in North Las Vegas.

            Water use in landscapes is driven by the number of plants growing there, their mature size and if they are desert adapted or not. Water use increases as the number of plants increase, the mature size of these plants and if they originate from the desert or not. Wise placement of these plants can create very pleasurable outdoor living spaces.

The Sonoran Desert has larger plants and more of them because it gets 250% more water than the Mojave Desert. Many people consider it a "prettier" desert because it has many more plants and the plants it has are more diverse in size, numbers and the kind growing there. More water means more plants and larger plants = prettier landscape and better soil.

            For every plant that survives in the desert, perhaps 1000 or more die because they don’t get enough water or are not established in the best location for their survival. Homeowners expect every plant in their landscape to survive.
            Plants make the air cooler. They transpire water from their leaves. This water loss from the leaves cools the air. And don’t forget the comfortable shade they produce as well.

A beautiful desert landscape that is also functional requires water but the water needs to be put in the right locations to get the desired results. An example is this landscape finished by one of my students in my landscape design class from several years ago.

            Water and comfort are trade-offs. To get the cooling shade from a tree requires extra water. If you want trees to shade your home during the summer months, then this requires water. Do you want a garden? Butterflies? Hummingbirds? These add to our quality of life. This is not a frequent occurrence without occasional extra water to support this kind of habitat.
Insects like this mantid in one of my Sweet Acacia requires some refrain from applying pesticides to your landscape. Yes, those are my fingers and my friend.

            Good looking plants require water unless you like the look of our native plants growing with the limited supply of water. Trees like mesquite and acacia can look a little sad growing in the open desert. But in a wash with a perennial water supply from rain runoff, they can be full and beautiful to look at.
Desert plants are beautiful like this opuntia flower growing at the University demonstration and research Orchard years ago. But it requires some water.

            So, I doubt if you can have a good-looking, even sparse, landscape without some additional water. But you can certainly reduce the amount of water needed in your landscape by carefully selecting the plants you grow in your landscape and supply applications of water judiciously and at the right times.

Monday, May 20, 2019

Contorted Jujube Will Produce Fruit on its Own

Q. I have a Contorted Jujube, which is partially self-fruitful. I acquired a Lang Jujube, which needs a pollenizer tree. I don't really have space to plant the pollenizer tree close to it. What is the maximum distance I can plant a pollenizer tree from the other?
Fairly young contorted Jujube during the summer months. It is considered partially self fruitful which means it will produce fruit without another tree for pollination but produces more if a pollenizer tree like Lang jujube is nearby.

A. Jujube performs extremely well in our hot desert climate. It is also called Indian fig or Chinese date. It’s a good fruit tree selection if you like the fruit. Even if you don’t like the fruit, it’s a vigorous landscape tree if it is irrigated.
Fruit of contorted Jujube in both fresh and dried forms on the same tree. Both forms are desirable depending on your own tastes.

            The term “beeline” is a good one to remember. It’s more important to have the pollenizer tree in a “straight shot” from the other tree and not around a corner. Bees travel in straight lines for the most part.
Contorted jujube in winter after leaf drop.

            These trees are pollinated by honeybees and other insects during the early spring and summer months. So, if you don’t have pollinators actively working your landscape then fruit production will be low even if you have a pollenizer tree. Attract pollinators into the landscape by planting flowering herbs like rosemary and provide clean water they can haul back to their hive. Birdbaths work with some rocks placed in the water as landing pads for the bees.

Different Cacti Require Different Exposures to the Desert Sun

Q. I have a cactus garden that faces west. Every summer I hang sheets on a clothes line in front of the cactus because it always looks like they are starting to burn up from the direct sun and heat.  If I don't protect the cactus this year, will they die?
Young Joshua tree, a Yucca native to the Mojave Desert, will handle tough landscape exposures with direct desert sunlight. Photo taken at the Las Vegas Springs Preserve.

A. It’s difficult to say without knowing which cacti you have. Not all cacti are the same and handle the Mojave Desert with ease. Cacti available from retailers are from a wide range of habitats. Some of these habitats are not as environmentally extreme as our own Mojave Desert. 
Cactus garden at the Las Vegas Springs Preserve

These cacti may show signs of stress when plunged into our Mojave Desert climate and soils. Cacti that originate from other areas may be more tender to Mojave Desert conditions. Discover which cacti you have and their place of origin.
Although not a cactus, this yucca is native to the dry sand dunes of the southeastern US and is damaged by the intense sunlight of the Mojave Desert if planted in the wrong location in a landscape. Yucca is oftentimes grouped with cacti.

Of course, cacti native to the Mojave Desert have a much better chance of survival without protection than cacti imported from other deserts with a milder climate. I would recommend using these if available. 

You might have to relocate some of your more temperamental cacti into a milder microclimate in your landscape. Find an exposure on the east side of the home or under some light shade. Most cacti can be relocated during the heat of the summer months.

Rescue Native Desert Cacti from Destruction

Q. Is it possible to transplant chollas and wildflowers? I live in a subdivision that will be excavating these beautiful plants to pave streets so I was wondering if it’s possible to transplant them and if they will survive after transplanting.
These "Teddy bear Cholla" can be rescued from construction sites with a little bit of advanced planning and careful management.

A. Yes, it is possible to save many of them but it will be a challenge and you have to know what you're doing. Years back I worked with a former NDOT landscape architect in preserving native plants when the road to Searchlight was widened. They attempted to rescue valuable native plants prior to construction by excavating and placing them into a nursery until they could be relocated.
Smaller cacti and succulents are easier to save than the larger ones.

            Contact your state’s Bureau of Land Management, Native Plants Program for information about native plant rescue. Native plants are protected and permits may be needed.

NDOT Native Plant Rescue near Searchlight, NV

            It’s not an easy task and requires specialized knowledge. Not all the plants will survive after being rescued. Be prepared for that. There will be some plant mortality regardless of how careful you are. Native plants have extensive roots that developed for survival under extreme desert conditions of low rainfall and high temperatures.
NDOT Revegetation project near Searchlight, NV

            A local landscape company called Trident Landscape Management has experience relocating native plants into residential landscapes. It’s the only one in the area that does, to my knowledge. The owner has experience and knowledge about rescuing and using native plants from our Mojave Desert and has participated in relocating them. I would recommend involving them so they have the best chances for survival.
Pete Duncombe and Trident Landscape Management 

Annual wildflowers are probably best saved by collecting seed. There are a few Mojave native woody plants and perennials available in local nurseries. The Nevada State Division of Forestry has a nursery in Floyd Lamb State Park that propagates and sells many native plants to the public. Consider supplementing your landscapes with these plants if they are not available through local nurseries.

Water Droplets on Grape Leaves May Be Pearls

Small water droplets can sometimes be found on well watered grapevines early in the season. These are not insect eggs but "grape pearls" as they are called.

Q. Early in the growing season I saw small clear droplets on my grapevines. Would you happen to know what is the source of these drops?  I have had leafhopper issues in the past and I was concerned they might be insect eggs.
Grapes early in the season can develop small balls of water droplets on the leaves and stems called grape pearls. They may resemble insect eggs but they are not and can be ignored.

A. Not too many people see what you saw. We are too busy to notice. These droplets are tiny and difficult to see. Not all kinds of grapes seem to have them. You might see them on Concord or Thompson seedless. Nothing to worry about but it is an interesting phenomenon.
            They are called “grape pearls” or “sap balls” and not related to insects or diseases. However, they do look like insect or mite eggs.  Leafhopper females lay their eggs inside the leaf veins so there are no eggs of this insect to see on the underside of leaves.
Leafhoppers are tiny jumping insects found on many plants including grapes. When they feed on the leaves, the leaves develop a yellow mottled look and black spots are left behind from their feeding with heavy infestations. At this point there is nothing much to control and except for hard pesticides.

            These droplets are pushed outside the leaf when the vine is full of water and experiencing rapid new growth. They are usually found on the undersides of leaves or on young stems. It reminds me of the water droplets pushed out of turfgrass through hydathodes in the spring during cool weather. There is so much water present on grass leaf blades that golf course superintendents would send someone out with a bamboo pole to “whip the greens” and remove the “dew” on the grass.
            Don’t be concerned and ignore them. If your grapevines are dense, shake the vines so water drops to the ground. Otherwise they will dry normally and disappear as the daytime air gets hotter and drier.

My Opinion of Pines for the Hot Desert

Q. What is your opinion of pines as landscape trees in our desert climate? We have quite a few planted in our complex and our HOA is discussing whether we should get rid of them or not because of their liability and water use. Our landscaper tells us they have borers.

A. I’m a little suspicious of the borer diagnosis in pine trees since it is rare for them. Have that diagnosis confirmed with a second or third opinion. Aleppo Pine gets a blight that causes browning of needles and entire branches.
Probably Aleppo Pine blight

            From a distance this can look like borer damage. So far no one has discovered the cause of Aleppo Pine Blight or how to control it but it’s thought to be related to irrigation and not resulting from a pathogen or borers. Aleppo Pine Blight is so common in the Las Vegas Valley that if a pine tree has brown branches, it is an Aleppo Pine, not Mondell.
Eldarica or Mondell pine will get dieback in some branches as well but not as well documented as afghan (halapensis) pine blight

            My opinion of pine trees used for landscaping in the desert is mixed. I don’t think large pine trees should be planted here but I do understand their light shade value once they have become established and mature. What makes me hesitate is their removal I’m not sure if the shade they produce is worth the extensive deep watering needed to keep them healthy and upright against strong winds. In some lower elevations in the Valley, these large pine trees with extensive roots may have tapped into shallow groundwater which could help with irrigation and staying stable.
Japanese black pine has a distinctive look that attracts many landscape designers and architects. But in my opinion it is not a good choice for desert landscapes because of it doesn't seem to survive to maturity in our hot desert.

            Removing existing, mature pine trees from the property will increase the resident’s electrical costs used for cooling during the summer months. I would recommend that you transition your landscape to smaller, desert adapted trees that shade the south and west walls of your buildings and then possible pine removal. Once established, their shade will substitute for the pine trees and help reduce residential energy consumption.
Pine trees receiving adequate amounts of water develop a full canopy of needles and demonstrate good growth. But large mature trees need lots of water to stay healthy and deep irrigations to develop deep roots to withstand strong wind.

            It would be far better to plant smaller pines such as pinion and Italian stone pine if a pine tree is desired. Japanese black pine is sometimes recommended but look around. Do you see any older Japanese black pine in the valley? Many have been planted here. It doesn’t survive in the desert for any length of time so I would discourage planting Japanese black pine here.