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.

How to Make Larger Pomegranate Fruit

 Q. What should I do to increase the size of my pomegranate fruit next year? My soil has a red color.

Pomegranate flower

Pomegranate small fruit developing next to each other. Leave only one when they are small. Some varieties are more prone to this than others.

A. Red soil tells me you are probably not from around here and secondly, your soil has a lot of iron in it. This type of iron is not available to most plants because it is low in organics and the acidity is wrong. 

I also assume you are a backyard producer and not a farmer. My recommendations might be different if you had 50 or more pomegranate trees and were local.

Right now, since it is late Fall and it is getting colder and there are still leaves on the trees, there is nothing to do. To increase the size of fruit, focus on pruning, a fertilizer application, and don’t let the plant get droughty. You will see some smaller benefits by removing a flower for small fruit growing right next to another, some thinning and pest control.

First, don’t forget to sanitize your pruning equipment. 

Sanitizing loppers with 70% ethyl alcohol.

About a month before new growth begins in the spring, prune the pomegranate to 5 or fewer (yes, as few as one) larger stems coming from the ground. Remove all the remaining growth to the ground as well. From the remaining larger stems remove all side branches up to your knees. After this is done, spray the plant and the soil directly at its base twice with dormant oil before it begins flowering.

            When flowering first starts, apply fertilizer to the tree 12 to 18 inches from the stems and where the soil is wet. Use vegetable or rose fertilizer if you do not have a fruit tree fertilizer available. Because your soil is red and not brown, consider applying compost instead of mineral fertilizer. If you apply compost, apply one cubic foot of it in a circle 18 inches from these large stems.

Apply compost to fruit trees, not pomegranate but you get the idea.

You might see a smaller benefit by removing flowers during the first couple of months which are produced very close to each other (if your variety does this alot) and controlling pests when you spot problems. If you are an organic gardener, consider using a Dust Buster for removing larger pests instead of insecticidal sprays.

Asparagus Failure in Las Vegas and How to Prevent It

Q. As an avid killer of plants I can't seem to get anything to grow outstanding well.  My asparagus attempt is especially disappointing.  I did as you suggested, mostly, and dug down as deep as my tiller would dig about 13".  For better drainage I 2" drilled holes another 12" and filled them with gravel.  I feel that should be pretty good drainage. I ordered Jersey Knight asparagus and planted as per instructions. I had a very mixed bag.  Out of 10 crowns 5 have died.  1 shot up like a cannon but has since slowed its velocity.  The other 4 are in some stage of growing but not heartily. How do I figure out what I did wrong 9 times and right once?

Jersey Knight? This is a Rutgers release as are all the "Jersey" types. In my opinion it has lower tolerance to desert heat than UC151 types which were bred in Riverside for the Coachella Valley. Eastern US, use Jersey types. Hot western areas of US, use UC151 types. They hold their spears longer.

These should be very vigorous if the soil is amended properly and watered like they are growing in an irrigation ditch.

Put asparagus crowns on their own valve OR put them on a tree valve but not a valve used for growing vegetables in vegetable beds.

Planting depth for asparagus crowns is anywhere from 8 to 12 inches deep. The reason for this is because the crowns get bigger over time and planting them deeper helps them to last longer, over 25 years.

A. Usually the reason for losing asparagus is watering them too often or bad drainage. The gravel was not a good idea. It did nothing for drainage and made it difficult to get straight spears if it improves drainage. If the soil has bad drainage then plant them on a mound about 12 inches high and 24 inches across. Plant them about 8 inches deep. 

Planting asparagus at the University Orchard in North Las Vegas.

Water and don’t water them again until the soil dries out in the area of the roots. How to know that? Use a soil moisture meter like you use for houseplants Buy them for $10 at Lowes or Home Depot. 

Make sure it works. Those made in China sometimes work and sometimes don’t. That's been my experience experience with well over a hundred of them. If the needle moves when you grab the tip it is probably okay. Otherwise stick the tip in a glass of water. Measure the soil moisture about 4 inches deep and water again ONLY if the needle gets to 5. Water them by hand if you have to and don’t hook them up to a valve that waters something else. They are always wrong for asparagus.

 'Purple Passion' asparagus spear straight as an arrow and long because the soil was sandy and not full of rocks.

Pomello Flowering in October in Las Vegas

Q. My little pummelo which came bare root in March has profuse flowering now in November.  The tree is small -5'- and would not support any pummelo sized fruit. Should I wrap it up for the winter and disregard the flowers?

Pomello is a distant relative of grapefruit and enjoyed in many SE Asia countries like on our farm in the Philippines. Its tolerance to freezing temperatures is better than most limes but not as good as some oranges. Its chilling injury (refrigerator temps, think banana) is not well known but suggests it may exhibit chilling injury. Pomello grown in the Las Vegas area.

A. In this particular case I don’t think any of the flowers would have set fruit anyway. Pomello that I know takes about six years to bear fruit. It may flower earlier than this but the fruit have to be pollinated and not abort the fruit.

 

Yes, protect the tree this winter if there are threatening temps below freezing. 

I don’t know about chilling injury (temperatures not freezing but refrigerator like) to this fruit tree but there are some suggestions that it exists.

More information on chilling injury of pomello

https://allfruits.blogspot.com/search?q=pomello  

More discussion on freezing injury of pomello

http://tropicalfruitforum.com/index.php?topic=24319.0

Pomello growing in the Philippines.

A. 

 

What To Do with Ash Trees That Have Scorched Leaves

 Q. I think you addressed this not too long ago but I give your Saturday articles to my neighbor so I’m not sure what you said. The attached photos show two trees the builder put in my front yard two years ago.  I think they are Texas Ash?

 Ash trees with leaf scorch. Most likely this microclimate in the landscape is too hot for this tree.

Aha. This is a hot location if it is south or west facing. The irrigated area under this ash canopy is too small. Expand the area and apply water to a wider area.

I have three yellow emitters and now water these trees twice per week for 15 minutes.  (I can’t remember how many gallons the yellow ones due in an hour)!

A. Ash trees don’t like the heat all that much. All of them including Arizona ash. So surrounded by rock (even though it is five feet away from the trunk) is not the best thing for it. The roots of this tree can't keep up with the demand by this tree for more water. The main reason you are seeing the leaves burning on the outside (leaf scorch) is either because the soil needs improvement or the soil is staying too wet or both.

If you can make that basin covered in wood chips about three feet wider from the trunk it will help. Rake the rock back, get more scalloped pavers and make it bigger.  Also, the wood chips should be about four inches deep. Keep the wood chips from the tree trunk about six inches.

It helps to put a thin layer of compost on the soil surface under the wood chips. If this is a burden then sprinkle it on the top of the wood chips and water it in with a hose. Mixing it into the hole at planting time should have been done at planting time but some of the less expensive plantings (I have heard rumors of this happening with some “special deals” from nurseries) don’t use much amendment at planting time or not much mixed in the soil or the holes are dug too small or all of the above.

I am not sure how you are watering that tree (one of the ash). There needs to be AT LEAST four drip emitters to that tree at planting time about 12 inches from the trunk and enough water applied to wet the soil 18 inches deep each time you water. After the first couple of days the watering should NEVER be daily. The first couple of days daily watering is okay to get the soil wet and get rid of air bubbles. The soil needs to dry out between irrigations. 

A long piece of rebar or any thin piece of steel can be used to judge how deep the water gets after an irrigation. Shrubs less than 3 feet tall irrigate to 12 inches deep, medium sized shrubs and trees to 10 feet tall irrigate to 18 inches deep, if 20 feet tall then water to 24 inches deep and big trees water 36 inches deep.

Use a four foot piece of rebar from Lowes or Home Depot to judge if watering is deep enough. If not, water more minutes or add drip emitters or get some that deliver more water until it gets that deep.

In mid summer three times a week is plenty if they are all alone and no other plants for the ash tree roots to get water from. Right now once or maybe twice a week is plenty. In about two or three years you better add more drip emitters in another ring out past these emitters about 18 inches away. 

Desert Horticulture Podcast: How Much Water Should I Give My Landscape Plants?

Learn how much water to give your landscape plants and when to do it on this episode of Desert Horticulture.

Stay ahead of the drought curve and water when it is windy. Don't wait for the next irrigation cycle.

Desert Horticulture Podcast: Ash Trees for Desert Landscapes

I received a question about ash tree flowers from a reader but I thought about ash trees in general. This podcast talks about my concerns when planting ash trees in any landscape in the desert southwest.

 

Desert Horticulture Podcast: Growing Herbs, Greens and Microgreens in the Desert

 Diane and Tom have been growing herbs, greens, and microgreens in the desert and marketed them to chefs, restaurants and homeowners for decades. Learn what has worked for them and why. 

Diane and Tom working in their Boulder City, Nevada, herb and greens garden. The growing area is protected from birds and other varmints by screening. Ground squirrels were particularly troublesome this past 2020 and they were relocated to a different part of time.

Diane tending one of her herb beds. The soils are enriched with compost, woodchips, alfalfa hay and all natural fertilizers. Raised beds are protected from birds by screening and the woodchips enriched the soil in the growing areas.

Overhead irrigation is preferred for watering as it gives better water distribution for the seedlings and transplants.

You can see that this way of gardening stimulates herbs and greens which are supplied to local chefs and restaurants as well as the public through local farmers markets.

Inside the "greenhouse" which is used primarily for raising microgreens and transplants. Not much light is needed during the summer. This temporary greenhouse is cooled and the humidity raised with swamp coolers. The covering is polycarbonate. Those plants needing more light are grown closer to the sidewalls.

Seeds for microgreens are soaked overnight in sanitized buckets for sprouting and then seeded in sanitized trays.

When to Plant Pomegranate in the Fall

Q. I would like to plant a pomegranate tree this Fall but I am worried that the weather is going to be cooling down soon. Do you think I missed my opportunity for planting, and should I wait for Spring?

Young pomegranate trees vary in cold hardiness but most like to be planted with woodchips rather than rock as a mulch.

A. Just because it is getting colder doesn’t mean you can’t plant. Ideally you want a few weeks of root growth in the Fall after planting. The timing may not be optimum for root growth when soil temperatures are cold, but it will still work out. If you find a variety you like, get it in the ground.

            Temperate plant roots (like pomegranate) grow best when soil temperatures are between 60 to 75F but they still grow even when soil temperatures are as low as 45F. They just don’t grow as fast. Try to plant early enough so that there are 4 to 5 weeks of warm soil temperatures before the soil gets cold.

            How to estimate the soil temperature? The best way is to buy a soil thermometer for about $15 and measure for yourself but otherwise you can make a rough approximation. Surface mulch, rock or woodchips, conserve soil warmth in the Fall and insulate soil from heat in the Spring and Summer months.

            In my experience, using your sense of touch is accurate to within about 5 degrees F of temperatures ranging from the refrigerator (40F) to the spa (105F).

            Fall planting (early) is always superior to Spring planting (late) of winter hardy plants.

Is Xtremehorticulture Advice Transferrable to St. George?

Q. I live in the St. George Utah area and use your horticulture advice regarding many of the plants in my yard. Three small questions if I may ask?

1) Is your advice, on the broad list of subjects flower-plants-shrubs- trees, ok to follow for this area?

2) I have never raised vegetables before and would the Moapa publication be a good guide for this area for a beginner grower?

3) I have two Arizona Ash on my South West side of the yard. 15 ft apart on a drip line. One had aphids this year which I watched closely and removed them with chemical spray.  However, the lower limbs continued to have leaf curl all summer with no bugs and no real damage to the leaf other than the curl.

A1. I view your climate similar to Kingman AZ and Pahrump NV. It doesn’t get as hot as LV and it can get a bit colder. You have an excellent extension guy in Rick Hefflebower located on the way to Hurricane. By all means use my information as best you can but if you aren’t sure about something run it by Rick and get his take on it. I think your soils are better than LV and you may or may not need as much soil amendment as we do in LV. The color of your soil should tell you. Certainly if you are growing vegetables or annual flowers you ALWAYS will need to add it.

A2. I attached his pamphlet for you and my planting calendar. whenever you can get local information is usually better.  You have some excellent gardeners in Washington county. I think Dr. Wittwer has some excellent info in his Moapa Valley vegetable guide but just tailor it to your climate. I think you are colder than our 3000 ft elevation I have on my calendar. I could be wrong but that is my take on it.

A.3. I think you may be more isolated in St George regarding ash decline but that is always my concern in the LV area. I saw this ash disease active in the LV community in the late 1980s so it is coming if you don’t have it.

The use of chemicals or not is a personal choice. I don’t support one side or the other. I use chemicals when all else fails. I don’t believe in throwing out the baby with the bath water.

Probably the biggest factor is wind. If its windy then irrigate that day and throw out the one day between irrigations rule. Listen to my podcast on heat and plants and it will apply to St George I think.

 

Desert Horticulture Podcast: What To Do in the Fall

 Fall months are busy in desert residential landscapes. Learn what you should be doing this fall in your home landscape.

When to Harvest European Pear

Q. I have a ten-year-old Bartlett pear tree and the pears are kind of small, about 3 inches long. The label says they ripen in August but mine are not ripe until end of October. November. I pick them, leave them out in kitchen and they become juicy and ripe. I water the trees heavily once a week and the fruit improve. Is there any way to make tree produce larger fruit?

Comice pear growing in southern Nevada.

A. Bartlett pear has the potential here for getting the same size as in the stores with the same or better quality. It is a matter of how many fruit there are compared to the number of leaves. If there are a lot of fruit and not enough leaves to support the fruit, the fruit will be smaller. 

Harvested Bartlett pear in southern Nevada.

            For Bartlett pear you should have about 45 to 50 leaves for each piece of fruit so that they can get larger. The fruit is produced on spurs that form an average of five fruit per cluster. Remove all but one fruit per cluster when the fruit has recently set and is still very small. This may be hard to judge when the fruit is just starting out in the spring but try removing all but one of the fruit in each cluster. If you want the fruit larger, next year remove more. Do it when they are small. Don’t wait. The remaining fruit will get larger. This is called “thinning the crop” or just plain “thinning”.

            Fruit also needs water present to expand and get big when its growing. Make sure the tree gets adequate water while the fruit is enlarging. If the tree doesn’t, the fruit will not grow as much. I don’t know if your watering is often enough or not. But in midsummer I would guess the trees should be watered deeply two or three times a week. Once a week is good in the Fall when it cools off.

Bartlett pear ready for harvesting, still immature yet for fresh eating.

            Pick Bartlett pears when they are still green, but the green has changed from dark green to light green. Your label is wrong. Harvesting should be in about late September or early October, not August. If you aren’t sure, pick one and cut it open to look at the seeds. The seeds should be all brown then go ahead and pick them. Picking may last two weeks as they don’t all get ready to pick at once.

    Pick the fruit before they turn yellow because this keeps the fruit texture buttery instead of gritty. Then let them ripen in a cool place out of the sun until they are ready to eat in a few days. When you get them from the store they are sometimes green. Ripen them like that before eating them.

Controlling Whiteflies on Pomegranate

Q. This past year our pomegranate bush had a lot of whiteflies. I know they do damage to the bush and so I want to control them organically and naturally. How would you suggest doing that?

Whiteflies on this pomegranate were diagnosed to be Ash whitefly by a USDA entomologist.

A. Whiteflies are a bad insect problem for any plant. I would rank them with the “hard to control” list of insects. In small numbers they can be tolerated but their populations grow so quickly that small numbers lead to large numbers very fast. For this reason, it’s important to get them under control early, as soon as you see them, in late spring and early summer. Don’t wait.

            Damage is associated with their feeding. Their feeding supports a quick growth in their population as summer temperatures get hotter. They love the heat and so they’re not seen around much until June or July. Once you see them and it’s hot, watch out! You are behind the curve and they are way ahead of you!

            In late May begin weekly inspections of the leaf undersides for whitefly adults. The adults look like living dandruff. You probably won’t see the eggs or immature forms because they are so small, but you will see the adult females preparing to lay eggs or protecting their young so that they can build their populations as quickly as possible. Pull these leaves off when you see them infested and dispose of them or vacuum them with a Dust Buster. This practice slows their populations way down.

            Control is two-pronged. First, spray pomegranate bushes on a warm day in December and then again in January with a dormant oil. You can use the commercial brands of dormant oils and horticultural oils or you can use soybean oil, canola oil, rosemary oil or cinnamon oil. 

Horticultural oil aka dormant oil are used for fall, winter, spring and early summer insect control.

Spray all the branches after pruning, top to bottom, and spray a little extra shot at the base of each tree. This spray suffocates insects that might be hiding out during the winter months. It is the most important spray for controlling insects that will be problems in 2020.

            At the beginning of June, hang bright yellow or bright blue thick construction paper in the tree smeared with Vaseline. Whiteflies fly toward bright yellow and bright blue objects and the Vaseline causes them to get stuck. As these traps begin to fill, replace them with new ones. It might look a little funny, but light reflected from aluminum foil repels them.

            If populations are totally out of control, spray with an insecticide to get their populations back under control. As a homeowner, use pesticides when all other attempts fail. Spraying with insecticides, however, have other consequences and should be a last resort.

What are Whiteflies and What Do They Look Like?

Q. In a previous post you talked about whiteflies. 

https://xtremehorticulture.blogspot.com/2015/02/how-to-control-whiteflies-on-tomato.html

https://xtremehorticulture.blogspot.com/2015/06/the-whiteflies-are-coming-whiteflies.html

What do they look like and how do I know if my plants have them?

Whiteflies on pomegranate

A. Whiteflies are commonly found on many different vegetables during summer months, like tomatoes, squash and melons. But they are not as common to ornamental trees and shrubs. As far as ornamentals go, they can be a problem for ash trees, citrus, pomegranate, gardenia, hibiscus, iris, flowering annuals, gladiolus and some others. Whiteflies are small insects, brilliant white in color as winged adults, that suck plant juices from leaves and young stems much like aphids and leafhoppers.

            If you are observant and constantly tinkering around your plants, you will notice them during the heat of the summer swarming in the air when disturbed from plant leaves like white “dandruff”. This is an indicator to look at the undersides of leaves where you will find a massive number of unwinged young’uns sucking “juice” from the plants.

            If you are not as observant, you might notice sticky, sugary sap dropping on plant leaves from the feeding just above it. Or you might see columns of ants attracted to this sugary sap, going back and forth to their underground nest carrying this sugary food. Sometimes a black mold will grow on this sugary sap in more humid climates, just like it will with aphids. This black mold is called “sooty mold” which can cause lots of plant damage if left unchecked.

            The adults can fly while the young-uns can’t.  So that swarm of white adults you see flying are adults only and a sure sign that feeding damage is underway.

            It’s winter now so you will not see whiteflies on plants unless they are on plants in warm spots like greenhouses. They are tough to control because they are resistant to  many chemical controls. If you find them early enough, removing infested leaves might keep them in check. Repeated soap and water sprays will kill them. Winter applications of dormant oil to woody trees and shrubs in January will help suppress their numbers in the summer from overwintering adults.

Dont Dig Deep Hole for Fruit Trees

Q. I am planting a 15-gallon ‘Wonderful’ pomegranate and suspicious if the plant would benefit from a deeper hole amended with washed sand to help with drainage.

A. Unless there is a drainage problem, 99% of the time there is no benefit from digging a hole deeper. There is even less benefit when adding sand to the hole in any form and this practice is likely to make drainage worse! When drainage is a problem, the simplest method is to plant on mounds.

            The majority of small tree or la
rge shrub roots are about 18 inches deep. That’s all. But the soil they are planted in must drain water or the roots will suffocate or “drown”. To check for drainage, dig a hole to the same depth as the 15-gallon planting container. Fill the hole with water and let it drain. Fill the hole a second time and watch how fast it drains. Filling this whole a second time is very important because the first filling only measures how fast water enters the soil or its “infiltration rate”. Filling the same hole a second time, when the soil is still wet, measures true drainage or its “percolation rate”.

12 year old fruit tree removed and showing the depth of its roots. Most fruit tree roots are about 18 inches deep. So wet the roots to 18 inches on fruit trees like pomegranate.

            If the water in the hole drains overnight, its drainage is acceptable. Only very shallow rooted plants like lawns, vegetables and annual flowers are watered daily during the summer months. When watering trees and shrubs the soil should be drained for at least one day between irrigations. This gives they soil and roots a chance to “breathe” before the next irrigation.

            Take my word on this but adding sand to a planting hole, either as a layer or mixed with the existing soil, is a recipe for disaster. Adobe bricks are made from a mixture of soil, sand and organics. Keep that in mind.

 

How Long to Get Figs from New Fig Tree?

Q. We're considering planting a fig tree grove in our school garden this year. How long typically does it take for them to produce figs ready for harvest?

Main crop of figs growing on new growth.

A. Figs produce fruit very quickly after planting. You should start seeing fruit produced the year after planting in most varieties. Remember, figs produce fruit on the wood that grew last year as well as the wood actively growing.

First crop of figs (Briba crop) growing on older wood (right) while the younger crop of figs (Main crop and left) is alongside the older crop. Look at the age of the wood they are growing from.

            Figs can be very big trees if you allow them to grow. They can also be cut back to a much smaller size. You mentioned planting a grove of figs. Their planting distances apart should be the same as their maximum height. If you plant them 10 feet apart, don’t let them grow above 10 feet tall.

The main crop of figs (not the first crop) will dry up and get hard if you dont give the tree more water as it gets hotter!

            Remember that figs do great in desert climates, in desert soils, in the desert heat with low humidity. But they are heavy water users much like palm trees. Water them the same as you would any other fruit tree and don’t expect production if you don’t give them enough water. They will benefit from soil covered with woodchips simply because the woodchips keep the soil moist longer. As the main crop comes on, they may dry up. This is because they dont have enough water to fully develop!!!