Grape Diseases and Bunch Rot

Q. Two years ago I had grape bunches that were shriveling up in the middle of summer while they were still green. I think it was a disease, but it spread and killed off nearly all my grape bunches. How can I prevent this in the future?

Grape diseases can be divided into two main groups; those that attack the fruit and those that attack the vines. This is a bunch rot disease of grapes in Las Vegas. The link is only for Botrytis bunchrot disease. There are several kinds.

A. Grapes don’t typically get borers, but they can get diseases that attack the bunches or young stems. Another disease attacks the new growth. The other problem commonly found on grapes growing in the desert is damage from our intense sunlight.

This was unofficially diagnosed as Eutypa disease on table grapes, a trunk disease of grapes.

            The most common diseases of grape bunches are the so-called powdery and downy mildews. You will not see them, but the disease is flourishing, invisible, right under your nose. This might be a problem later with grapes when there is snow or rain falling on the new growing vines in the spring. It will cause the bunches, all of a sudden, to die green.

During February and March, hope for dry weather when grapes are first starting to grow. If this kind of weather is present then, it’s a good idea to spray a fungicide two or three times during the growing season to prevent bunch diseases like these from becoming a problem. Spray the first dose when bunches are small to protect them from infection. The usual fungicides for homeowners are copper fungicides like Bordeaux. And for heaven sakes, when you are pruning, sanitize your pruning shears

Damage to the bunches or older stems from intense sunlight is not a big problem if grape stems and fruit are grown in the shade of their own leaves.

About the only chemical protectants you can spray as a homeowner are the copper based fungicides, Bordeaux probably leading the group. Remember, fungicides like Bordeaux are protectants and much more effective at protecting new growth from infections. Watch for wet or rainy weather during new growth. If this happens, it is much more likely a disease will occur. Spray with Bordeaux mix after new growth has started and then again as the berries start to enlarge.

Getting Larger Berries in Your Grape Bunches

 

'Flame' table grape growing in Las Vegas.

How do those grape berries get so big in the grocery store? Yes, its true they sometimes use hormone sprays to increase their size but you can do it naturally. Whether you are growing wine grapes or table grapes, it is important to "thin" the fruit to get larger or more flavorful berries. In table grapes the result is larger berries. In most wine grapes, the berries will not necessarily get larger (berry size is ultimately regulated by genetics) but they will get more flavorful.

Here is how.

Fewer Bunches Make Larger Berries

"Balance the fruit load." It is important in wine grapes as well as table grapes. That is a common moniker but what does it mean? It means to reduce the total number of bunches growing in each vine. The minerals taken up by the roots are divided up into fewer bunches and consequently fewer berries. Figure one good sized bunch every 6 to 8 inches.

Reduce Bunch Size

This is done by "pinching" or removing the bottom of the bunch when very young. Sound familiar? You do the same thing to peaches, plums and apples. Then it is called "thinning". The concept is the same. Fewer "mouths to feed" results in larger fruit. The same is true in grape berries. If you reduce the number of bunches AND remove the bottom third of each bunch, the remaining individual berries get larger.

Pinching or removing the bottom third of the grape cluster results in fewer berries and the remaining berries can get larger.

Variety Determines Results

The ultimate berry size is governed by its genetics. The variety 'Italia' is a seeded white grape that grows well in the desert and can be used for fresh eating or making wine. It can get very large berries. While the variety 'Pinot Noir' doesn't seem to get a much larger berry size by thinning but the flavor is more flavorful!

Fertilize and Increase Watering as Grape Growth Appears

Q. I have a grape, with dark colored fruit, growing on my established trellis. It’s already pruned. What should I do to it now?

Fantasy table grape growing in Las Vegas.

A. Of course your grape plant will need water and fertilizer when it starts growing in March. I would apply the fertilizer the first week of March and begin watering weekly during February.

As new growth appears, you should already be watering once a week and have any fertilizer applied. to help push new growth.

Which fertilizer to use? Any fertilizer used for fruit trees will work. It’s applied where the water is delivered to the plant but at least 12 inches away from its trunk. I prefer using a rich compost as a fertilizer instead, but it must be watered beyond any surface mulch so it comes in contact with the moist soil underneath it.

Whether you apply compost or mineral fertilizers to help new grape growth push, do it just before new growth appears for best results.

Grapes grow better in the hot desert if there is “plant litter” (surface mulch) on top of the soil where they receive their water. This surface mulch of 3 to 4 inches deep helps keep the soil surrounding their roots moist and cool. Woodchips from landscape trees make an ideal surface mulch for grapes and fruit trees because they easily rot and decompose into the soil.

Wood, whether its from "forests" or urban forests is a valuable and rare commodity in the desert.

Here woodchips are being dropped at the Ahern Orchard in Las Vegas to be used for soil enhancement around fruit trees and grapes.

It’s helpful to determine if your grape should be “spur pruned” or “cane pruned”. Bunches of grapes are always produced along last year’s growth. The difference when pruning different types of grapes is where the fruit is produced along this new growth. Spur pruned grapes produce their bunches at the base of last year’s growth. Cane pruned grapes produce their bunches from buds further out from this. Buds that produce grape bunches further out, when spur pruned short, are void of grape bunches. Pay attention to your variety of grape and whether it prefers spur or cane pruning.

Grapes and fruit trees grow much better and with fewer problems when NOT grown in bare soil but the soil covered in woodchip mulch.

Simplest way is to delay pruning until you see grape bunches starting to form. I know it can be heart-wrenching, just like thinning peach trees, but removing extra bunches will make each of the berries in the grape clusters larger.

When it’s an unknown grape variety I’m not sure about, I look for old grape clusters, remnants, produced last season. (I will take a few shots of this and insert later. I dont have any shots of this yet.) These can be subtle differences and not obvious to the casual observer. Count back the number of bumps or “buds” where these remnants were attached to older growth. Do this in several locations and get an “average” distance from where it grew. This tells you where you can safely prune last years growth and how much can be removed. Doing this can insinuate if a grape should be spur pruned or cane pruned in the future.

Delay Pruning Grapes in the Desert to Prevent Losses

            

Spur pruning of grape delayed until just before new growth occurs.

Whether you are growing wine grapes or table grapes, it’s a good idea in our climate to delay the final pruning until you are confident freezing, dry and windy weather has passed. The reason for this is to minimize fruit loss because of cold, windy and dry late winter and early spring weather. If you get eager and make your final pruning early, it’s possible that cold, dry windy weather later might eliminate some or all the fruit you intended to keep.

If grape pruning seems a bit daunting, go ahead and prune last years growth long (canes) even if your grape should be spur pruned. As the time approaches for new growth to occur, finish pruning with a second cutting of last years growth to the proper length. This avoids potential losses from the cold and dry winds that can sometimes happen in the desert.

All grape bunches come from buds on last year’s growth. In this way, fruit is produced much like fruit is produced by peaches and nectarines. But this is where the similarity stops. Some grape bunches (Zinfandel, Syrah and Muscat for instance) grow from buds very close to where last year’s growth began. These types of grapes are “spur pruned”; leaving less than an inch of growth remaining from last year.

Leave the canes a bit long and finish pruning when fruit clusters appear to "balance the load".

Other varieties of grapes (Thompson seedless and Concord grapes for instance), their bunches grow from buds several inches further out along last year’s growth. These types of grapes are “cane pruned” because last year’s growth is left longer; 6 to 10 inches in length. This allows the unproductive buds to grow without producing any fruit.

Grape bunches appearing in early May in Las Vegas.

            I delay pruning grapes in our cold desert climate as late as I can. Sometimes even after new growth is well underway. Delaying the pruning this long delays the chance of fruit loss because of freezes and cold drying winds. In the Las Vegas Valley, final pruning may be delayed until late February up until the first week in March. If you want to be doubly sure and a bit lazy about it, delay final pruning until fruit bunches show you where to prune. This might be as late as mid to late April or early May!

You can delay the final pruning of grapes until you actually see fruit clusters (bunches) appearing. Doing this can help balance the load of fruit and make larger berries in the clusters.

            This doesn’t mean you can’t do some pruning earlier. Just be careful and not remove too much of last year’s growth. It’s okay to leave last year’s growth about 12 inches long and cut it shorter than this when you are confident new growth is about to begin or later.

Cancer-Like Growth on Peach Trunk

Q. I have a woody cancerous growth coming from my peach tree trunk. Should I remove it or leave it alone?

Crown gall on peach tree

A. Judging from the pictures you sent, this woody growth looks like the early stage of bacterial crown gall disease. When the tree is older, this cancer-like growth can get quite large but it’s nothing to get overly excited about. It’s not a deadly disease like fire blight can be, but it does cause a gall-like growth of woody tissue near the point of infection.

Crown gall at the actual crown of a tree.

Sometimes it’s seen as a gall on the trunks of infected trees that were “nicked” with a dirty shovel that contacted the soil. In any case, break off this ball from the tree when it gets larger. It will grow back again.

Crown gall on the limb of a peach tree.

Fruit Tree Pruning for Beginners

            If you haven’t pruned your fruit trees yet, it’s not too late. Prune grapes as late as possible; toward the end of February or first week of March in the Las Vegas valley. More will be coming on grapes in the coming weeks. Final pruning of fruit trees for less experienced pruners is best delayed until flowers appear. It’s a lot easier then to see where fruit will be produced when actual flowers are seen.

If you wait to prune until flowers appear or start to swell it can be easier to see what to prune and what to leave behind.

Pruning fruit trees is a two-step process; the first step controls the size of older trees and trains the developing major limbs of younger trees to eventually support smaller branches and fruit. The second step in pruning focuses on spreading fruit production throughout the entire tree’s canopy. The first step is done any time after leaf drop in the fall but before flower and fruit production in early spring. As soon as the tree is pruned for size and major limb selection is established, apply dormant oil sprays for preventing many different types of insect damage in the coming months. Do this before flowering starts. These two steps can be done separately or at the same time. I suggest two separate steps for the less experienced.

Prune tree structure to either open center like this peach tree or modified central leader.

During the first three years after planting the focus is on developing the tree’s structure. While the tree is in its first three years, major limbs are trained by directing the limbs to grow at 45° angles from the ground. Ninety percent of pruning efforts during the first season focus on establishing the overall tree structure; about 50% the second season and about 10% the third season. Once the overall structure of the tree is established, very little of this type of pruning needs to be done in in the future. From that point forward, pruning is focused on fruit production. Pruning to control its size is done when the tree is over four or five years old.

This apple tree is pruned into a modified central leader structure because it wants that kind of structure. Peach grows more like a bush so it lends itself to open center pruning structure. No hard and fast rules to follow.

On peach and nectarine, fruit production should come from all parts along the scaffold limbs, not just the tips. Pruning for fruit production focuses on developing young, newer growth horizontally like a feather, with plenty of space between branches to allow indirect light inside the tree canopy. This means removing most upward and downward growth.

In the Mojave Desert because of our hot, bright summer sun, focus is on finding a “balance” between shading the limbs inside the tree as well as its trunk and opening the canopy for more light. This balances the trees need for sunlight with its potential damage.

Pruning and Painting Peach After Limb Breakage

Q. I pruned some fruit-laden heavy branches from my semi-dwarf nectarine tree during the hot summer months last year. I think I've damaged the tree. The leaves on a few branches turned yellow/orange while 80% of the other leaves look dead. Should I do some heavy pruning, or wait and see?

Limb breakage of peach due to heavy fruit load. Thin and prune. This opening can lead to sunburn on the branches and subsequent borer damage to the limbs.

A. Leave the tree unpruned this season to protect itself as much as possible. Let it send up lots of new growth this spring and hope for the best. Right now, the tree needs to shade its larger limbs and trunk to help prevent sunburn and prevent borers from attacking the tree. Scientists report that borers love to attack peach and nectarine trees where intense sunlight has damaged it. Borers are not controlled by winter sprays of horticultural oil.

Peach tree painted with white latex paint right after planting.

Paint the upper surface of exposed large limbs and the south and west sides of the trunk with diluted white latex paint. Painting or covering these areas helps reduce sunburn. Sunburn results from intense sunlight shining on exposed areas. Painting exposed surfaces of the tree with any light-colored latex paint mixed half-and-half with water helps reduce this damage. It won’t eliminate its possibility, but helps to reduce it.

Ready made white tree paint. It can be made by diluting white latex paint with water, 50/50.

As a precaution, drench the soil around the tree with a systemic insecticide for borer control. Do this immediately after the tree finishes flowering this spring. Don’t eat the fruit, produced this season, from this tree because the insecticide is systemic and likely inside the fruit. Most of it will be gone from the tree by the next growing season. Follow the label directions exactly.

Next season remove major limbs only during the winter months and always remove fruit from your tree when it’s tiny so as to reduce limb breakage.

Meyers Lemon Tree Needs Some Training

Q. I have a Meyers lemon tree that needs pruning. How do you suggest I should proceed?

A. Older citrus, including Myers lemon, needs little pruning once it’s over about four or five years old, if it’s been trained properly. When young, it should be trained to grow into a tree.

If your Meyers lemon looks more like a shrub than a tree, then prune it to one central trunk.

            The same structure used for training other fruit trees is applied to citrus; the central trunk has limbs removed from its trunk or multiple trunks up to about knee height. Limbs are removed from the trunk so that heavy fruit still attached to the remaining limbs doesn’t wind up sitting on the ground. Fruit touching the ground is more likely to spoil.

            While it’s still young, develop the main scaffold limbs that support new growth and fruit. These scaffold limbs should grow from the trunk or trunks “like spokes on a wheel”. Make sure these major limbs have at least 6 inches between them, originate in a spiral pattern from the trunk, and they are not growing on top of one another. When limbs grow on top of one another then shading and light distribution throughout the canopy is a problem.

            I always start inspecting the trees for good limb distribution at the bottom, usually on my hands and knees. First, I inspect the trunk up to my knees and make sure it’s “clean”. Next, I inspect the limb structure from my knees to my waist and make sure these scaffold limbs are well distributed. I fix any stems that are crossing over each other, broken, or creating too much shade.

If the tree is too tall, I remove upright branches that contribute to its height. These pruning cuts are made inside the canopy at “crotches” where two or more limbs come together.

Finally, I inspect the tree up to its top, looking for the same types of problems as before. After the structure of the tree is inspected, I then fix any problems with light distribution inside the canopy. After the fourth or fifth year, little pruning of citrus is needed.

How Often to Sanitize Pruning Equipment

Q. How often do you sanitize your pruning shears and what do you use?

Loppers are sanitized with an alcohol wipe before pruning begins for the day.

How to sanitize pruning shears

A. The primary reason I start my pruning day with an alcohol spray or alcohol wipes applied to pruning blades is for sanitary reasons. First, I clean the blades with soap and water and then sanitize them when finished. Chances are probably one in 500 that it’s not needed, but it’s that one case in 500 where sanitation is important because of diseases.

            I usually only sanitize the blades of my hand shears and loppers. I sanitize the saw blade only when it’s needed which is seldom if I prune every year. I start pruning with loppers first and finish pruning with my hand shears. Once the lopper blades have been sanitized, they are never placed on the ground again. There are at least five plant disease problems found in soil. Instead, they are hung around my neck or on a limb of the next tree I will be pruning.

            If a tree looks like it may have a disease problem, I sanitize equipment that I use after I finish pruning. If it’s a highly virulent disease like fire blight, the blades are sanitized between each pruning cut.

See the whole video on sharpening, adjust and sanitizing pruning equipment here.

Citrus Fruit Production in Southern Nevada

Orange tree growing in southern Nevada

Winter Low Temps

First of all, citrus production is not commercially done in southern Nevada. There are two good reasons for that. Citrus are subtropical and range from fairly tolerant of winter freezing temperatures (kumquat, Myers hybrid lemon, grapefruit and mandarins) to citrus that can barely tolerate freezing temperatures at all (sweet oranges like Washington Navel, limes, true lemon). Commercial citrus production occurs in Yuma, Arizona, and parts of southern California where it is warmer. 

Whether citrus survives the winter depends on the type of citrus, how cold it gets during the winter, if these minimum temperatures occur in spring, midwinter or fall, and how many hours it lasts. 

Sweet orange is tender to winter low temperatures in Las Vegas. Here the sweet orange died back to the more tolerant sour orange rootstock and it grew replacing the sweet orange.

The second reason citrus fail to produce fruit here is, like any fruit tree, due to late spring frosts when it is flowering. Flowers, unlike the tree, can't handle any freezing temperatures or the flowers die and dont produce fruit. 'The tree might be able to but the flowers can't. 

Flavor Supreme pluot in full bloom. The flowers of flavor supreme pluot and when they bloom make this tree irregular in consistent fruit production, year after year, in southern Nevada. Citrus like Meyer lemon can be the same.

If a light freeze occurs once during its flowering time, there is a chance some fruit will be produced. If light spring frosts occur repeatedly over a couple weeks of flowering then it is likely there wont be any fruit produced. If a heavy spring freeze occurs then the whole crop is lost and maybe even the tree!

Flowering is Triggered by Stress

Draping burlap over citrus tree for cold protection in Las Vegas. Draping burlap over the tree keeps the wind off of the tree and may help reduce flower freezing by a couple of degrees.

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But homeowners buy citrus from Las Vegas nurseries, plant them and wonder why they die or don't produce fruit. Flowering in citrus is triggered by stress, whether it is from cold or drought. The plant doesn't care. Both are forms of stress for the plant. In southern Nevada orange, grapefruit and mandarin characteristically flower for 2 to 4 weeks following winter dormancy or cold. Flowering starts just before a spring growth flush of leaves, commonly seen here in March. Out-of-season flowering is occasionally seen in June or August following a dry period. 

Sucker growth from trunk of Cara Cara Orange in southern Nevada

Lemons and limes also flower in the spring but may flower intermittently throughout the year. Kumquat does not produce flowers or have a spring leaf flush of growth until about May so it typically will have fruit regardless. On top of that it is one of the more cold hardy citrus you can grow in southern Nevada. Flowering will occur after a rain similar to a drought-induced dormancy in the tropics. There is often a main flowering period with the onset of rain after a long dry season and a small flowering period following the end of a rainy season when there are intermittent short periods of drought and rain.

Citrus leaves yellowing due to intense desert sunlight

Drought and Cold are Both Stressors

In Nevada orange, grapefruit and mandarin characteristically flower for 2 to 4 weeks following the winter dormancy. Flowering starts just before a spring growth flush of leaves, commonly seen in March. Out-of-season flowering is occasionally seen in June or August but that is following a drought and then and rain or irrigation. Lemons and limes also flower in the spring but may flower intermittently throughout the year. Kumquat does not produce flowers or have a spring leaf flush of growth until about May. Flowering will occur after a rain similar to a drought-induced dormancy in the tropics. There is often a main flowering period with the onset of rain after a long dry season and a small flowering period following the end of a rainy season when there are intermittent short periods of drought and rain.

Hobby St. Denis and grapefruit tree in Las Vegas, 1995

Flowers Produced at Different Ages

Orange and grapefruit trees require 6-12 years to flower and fruit after planting young trees. Pistachios will be about the same. But grafts from the flowering portion of an older tree takes only three or four years! But the lower, older portion of that young seedling tree remains juvenile forever in exchange. Mandarins take only 5 years to start flowering, limes only 2-3 years and Key lime 1 to 2 years. 

Once fruiting, most citrus are notorious for producing a smaller yield the following year after a full load of fruit. An example is the Murcott variety of mandarin. I tell people to not delay harvesting fruit from Myers lemon when ready because keeping fruit on the tree for a long time can result in smaller yields the following year. Myers lemon is ready to harvest in Las Vegas at the end of December to mid-January. When it is sweet to the taste, harvest the fruit.

Pruning Citrus and Fruiting

Pruning may delay flowering and fruit to the following year if its severe. It depends on the variety and how much pruning is done, but expect little to no flowering when trees are heavily pruned. Pruning citrus is done commercially to oranges and necessary for controlling the size of the tree and producing fruit regularly. But prune citrus with caution. Pruning can commonly result in reduced fruit and flowering on pruned portions of the tree. Annual or even every other year lightly pruning of the tree may be enough. Published research on best practices for pruning citrus is sparse.  

Leaf loss due to winter freezes can decrease flowering and fruit production. Occasional leaf loss due to winter or spring freezing temperatures may not be a problem but regular early fall leaf loss will. Excessive watering and applications of fertilizer seem to have little effect on fruit production.

Should Pine Trees be Grown in the Desert?

The major uses of pine trees in desert landscapes are for visual barriers, sun protection, windbreak, or mark property boundaries. 

Problems with Pines

They oftentimes become too large for the property. Cute when they are small. That is the problem now, they are large trees so you need a lot of space to grow them. And they use more water as they get bigger. And they need to be watered deep to improve their anchorage during strong winds. There are plenty of other choices that are smaller trees for shade and for visual barriers. As windbreaks? Put windbreaks close to where they are needed,  not on boundary lines.

Pine trees are frequently planted for shade but out of scale when they mature.

The two pine trees most commonly planted here, are the more formal looking Afghan (Pinus eldarica, sometimes called Eldarica or Mondell or Mondale pine) and the loosely structured and informal Aleppo pine (P. halapensis).

Aleppo vs. Mondell

The less formal looking Aleppo pine (P. halapensis)

The more formal looking, Christmas tree-like, Mondell pine (P. eldarica)

These can be fairly large trees at 40 feet tall and above and can easily dwarf a single story home. They can use quite a bit of space and, at those sizes, can use quite a bit of water when they get bigger. Its not a question about whether they will grow in the Mojave Desert but where will you put them?

Aleppo Pine Blight

They can look quite similar sometimes and telling them apart can be difficult. All pine trees can cross pollinate and are wind pollinated. But most of the time they are easy to recognize. One method I use to differentiate the two is the presence of winter physiological disorder called Aleppo pine blight. It only is present on Aleppo pine. It usually causes isolated browning of new growth in a patch or two here and there. In some cases, it can cause tree death but it is rare in Las Vegas.

Aleppo pine blight occurs during the winter and is a disorder that oftentimes causes isolated browning of new growth in Aleppo pine only. It can get so bad in some regions that it causes severe browning and suspected of tree death.

Chir Pine?

A vert large (60+ feet) and graceful pine sometimes used is the Chir pine (P. roxburghii). But this pine is a bit tender to winter cold (and in severe freezing temperatures (low 20's) can be damaged. Like many other plants, in its wild native habitat in the lower elevations of the Hindu Kush (northern India, Afghanstan and northern Paksistan) survives fire and will "sprout" new growth from its trunk if scaffold limbs are killed by fire or cold. Not to be confused with a very similar looking, long needled, but more winter tender pine called Canary Island pine (P. canariensis) heralding from...you guessed it...the Canary Islands.

Chir pine, considered perhaps subtropical, can be a bit tender in the Las Vegas area but it has a very graceful appearance if it survives the winter cold every 15 years.

Chir pine is one of the "long needled" pine trees that can have a very graceful appearance in the landscape but not nearly as tender as its very close relative, the tropical Canary Island pine and similar in cold hardiness to some of the more tender citrus like naval orange (P. canariensis)

This Chir pine survived but some of the branches froze. The mass of its trunk survived the freeze and sent out these suckers from epicormic buds embedded in the trunk. Fire and freezing temps can cause the same reaction.

Japanese Black Pine

Japanese Black pine is oftentimes recommended for planting in urban landscapes because it is a smaller pine (25+ feet) with an interesting form for landsapes. But when was the last time you saw one growing here? Nearly all of them planted here have died. Beware!

Japanese black pine.

Two Nevada State Trees

Bristlecone pine (P. longaeva) and Pinion pine (P. monophylla) are the two state trees of Nevada. Pinion pine occurs at around 4500 foot elevations in Nevada. Bristlecone pine much higher. For this reason, Pinion pine would  have a better chance in the hot, lower elevations of the Mojave Desert than the 6000+ foot elevation Bristlecone pine. Pinion pine occurs in the wild along with Utah juniper. The problem? Availability. It was popular for Mojave Desert landscapes about 25 years ago and disappeared from nurseries.

If you choose to grow pines in the desert:

1. Give them plenty of room to grow because they will be big trees.
2. Amend the soil in every direction around the trunk about 2 to 3 feet and a foot deep.
3. Cover the soil after planting with 3 to 4 inches of woodchips.
4. Water them with a coil of drip tubing or basin filled with water. 
5. Water them deep when you water - three feet deep!

Shade Cloth and Other Effects of Light on Plants

Sunlight can be very strong in the desert. In other parts of the country where sunlight is more "normal", shade cloth might not be needed. Desert sunlight can be very intense at times. It makes sense with some plants to reduce light intensity with shade cloth? But how much? Which plants?

Intensity

The effects of sunlight (or light) can be broken down into the quantity of light plants receive and the quality of this light. Light quantity refers to its intensity, or how strong this light can be. 

Intensity of sunlight refers to the quantity of light plants receive. Some vegetables give us better plant parts with a little bit of shade. This is 30% shade which is about right for a lot of leafy vegetables growing in the intense desert sunlight. This may be too much shade for some flowering vegetables like okra.

The 30% shade cloth was doubled over to give 60% shade in this darker area of the grow tunnel. Usually anything above about 40% shade will prevent a lot of vegetable growth and production.

Light Color

The color of light can also affect plant growth. Red light promotes flowering while solid blue light discourages flowering. Research has demonstrated that different colors of light in combination can promote certain types of plant growth. Should you as a homeowner use different lights? Probably not but it might be worthwhile if you grow plants commercially.

For more information look at https://sensing.konicaminolta.us/us/blog/can-colored-lights-affect-how-plants-grow/

At Dave Wilson Nursery near Modesto, CA, here red shade cloth is applied to influence plants.

How Long Light Shines (Photoperiod)

Plants will do different things sometimes at different times of year (mostly in cold climates, rain can play a similar role to light in tropical climates). Sometimes this is tied to how much night time there is or how much rain. Plants cant move around so they are much more "in tune" with their environment and "reading" it.

At this marijuana production facility light is used to provide the energy needed for plant growth. A certain light intensity is needed if any kind of production is needed.

Although not done here, a specific color of light could be used that enhances root production of these cuttings. Some decisions are better made considering the economics of production.

Crop Calendar for Yuma, AZ, USA.

 Yuma AZ is warmer than Las Vegas. Yuma sits on the border of Arizona and Mexico. Its latitude sits between 32 and 33 degrees North latitude (Las Vegas is closer to 36 degrees north of the equator). 

Yuma's elevation is only about 140 feet above sea level (Las Vegas is about 2000 feet above sea level). Both elevation and latitude play major factors in determining winter low and summer high temperatures.

Latitude and Longitude map of Arizona. Yuma AZ is near the border with Mexico and at 140 feet of elevation above sea level. Tucson AZ, even though lower in latitude than Yuma, is at 2400 feet of elevation above sea level which accounts for most of  its colder winter temperatures and warmer summers. https://www.mapsofworld.com/usa/states/arizona/lat-long.html

Because of its warmer winter temperatures, Yuma can grow some of the more tender nopales (such as Copena V1 and F1 and better tasting!) from Mexico than we can in our colder winters in Las Vegas. We can grow cold hardy nopales but they are not as tasty as the more tender Copena types. Winter freezing temperatures affect both pad (nopales, nopalitos) and fruit (tuna) production.

Freeze damage to Copena nopales growing in Las Vegas during the winter of 2007-8.

To make the planting/harvesting adjustment from Yuma to Las Vegas, consult local temperatures but it will be about 6 weeks forward in the spring months and about 6 weeks backward in the fall months.

Even though this crop calendar is for seed production, the planting dates would be the same.

 "Contracting" refers to the business arrangements needed for seed production to begin. "Sowing" refers to planting time.

https://www.condorseed.com/contract-production/ 

Are Food Forests the Right Thing to do In the Desert?

 Come join me in this podcast about exploring Food Forests in the Desert. Should we pursue this permaculture concept in desert landscapes?

Moringa leaves on our farm in the Philippines. We use the leaves of this tree for food and as a spice nearly on a daily basis. They are a commonly planted tree now in Southern Nevada due to food forests. But is it the right thing to do?