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!!!

 

Desert Horticulture Podcast: Desert Lawn Establishment and Maintenance

 Desert lawn establishment in the Las Vegas area is lucky (or unlucky) enough to be in the transition zone for establishing lawns; both cool season and warm season grasses can make lousy lawns. Come learn why on this episode of Desert Horticulture.

Shade Cloth for Figs? Interesting...

Q. I put up some shade cloth to protect my fig trees from the heat. The new growth is good and the leaves look fine so I don’t think its water, but I think they can’t handle this heat. I will take the shade cloth down after the temperatures come back down to maybe 100F.

A. I have grown 15 different varieties of figs over a period of 20 years and none of them needed shade cloth. They were all in full sun. They did however have lots of wood mulch covering the soil and regular irrigations applied when they were producing fruit.

            The usual problem with fig fruit drying up in the heat is a lack of available water in the soil. For several reasons this problem can be resolved simply through soil improvement. Figs are an “oasis” plant, similar to palms, and the organic content of the soil near sources of water is higher. Figs in those locations have access to more water and better soils.

            If you’re going to use shade cloth, never go higher than 30 – 40 %. When using shade cloth, achieve a balance between food production and food quality. In the case of figs, the fruit needs protection from birds rather than the sun.

Desert Horticulture Podcast: Pluses and Minuses of Artificial Lawns

 Learn the positives and negatives of artificial grass installed in the desert in this episode of Desert Horticulture.

Home Landscape with Magnolias and Rock

Q. We moved to Las Vegas four years ago and had a professional landscape our backyard. We now have eight magnolias as well peach trees throughout our backyard surrounded by large rock up against the trunks. This rock makes it difficult to fertilize the trees and pick the fruit. Our gardener told us the trees are not getting enough water. Should I pull the rocks away from the trunk of these trees and put wood mulch around their trunks?    

A. First off, both peach trees and magnolias will not like the rock laid on the surface of the soil and surrounding the trees. You will see them start to suffer from this practice in three to five years. Both prefer an “organic” mulch that can decompose into the soil and improve it. That means a four-inch-deep layer of woodchips.

            When buying peach trees, they should be on a semi-dwarfing rootstock such as Citation. If bought on this dwarfing rootstock, they can be planted about ten feet apart, pruned to keep them small, the soil enriched with a good quality compost at planting time and the soil covered with four inches of woodchips, not rock. So yes, pull the rock back about three feet from the trunk and lay down four inches of woodchips instead.

Young magnolia planted in fescue lawn in Las Vegas.

            Magnolias? Eight of them? Wow. I’m assuming you are talking about southern magnolia with its beautiful flowers. Even in Georgia, where they belong, one specimen tree is more than enough for a large yard. Magnolias growing in Georgia can get 75 feet tall with a similar spread! These trees are NOT meant for backyard, or front yard, landscapes (desert or no desert) unless you have a huge property and water is cheap.

            As these trees get older (if they do) they will become a nightmare to maintain and water. Get rid of them now before they get fully established. One tree is enough to satisfy your curiosity and you will probably remove it in less than ten years anyway.

            Let’s say you keep the rocks. Using large rocks around plants has both pluses and minuses. If they are large enough, fertilizer or compost can be flushed on to the surface of the soil by washing it through the rock with a stream of water from a hose. Large rocks are also great for keeping people out. But you are right. Large rock makes it difficult to harvest and prune fruit trees. In my opinion, rock larger than 3/8-inch diameter is difficult for walking safely.

Where to Get Good Vegetable Seed

Q. I have been looking for seeds for planting fall vegetables and herbs and not having much luck here in Vegas. Where should I start? 

A. Start with varieties that have done well here in the past. Dr. Wittwer’s Moapa Valley vegetable growing “Bible” is a good place to start. He mentions several older varieties that have performed well for him. I can forward a copy to you if you don’t have it.

            Slowly introduce new varieties that have no production history in the desert. Be careful. Not all varieties produce well in a desert climate. Consult online vegetable seed sources like Gurneys, Park Seed Company, Territorial Seed Company, Baker Creek Seed and Grow Organic. Specialty seed sources like Kitazawa Seed and Seeds from Italy provide some interesting and heirloom seed sources.

            Heirlooms don’t produce as much food as hybrids, but they are oftentimes “tastier” if you can get them to produce here. heirlooms are not as "finicky" as hybrids so they don't require as much fertilizer and care.

Sick Raywood Ash on a Cul-de-Sac

Q. We have four established Raywood ash trees on our small cul-de-sac. Three are doing fine but the one directly in front of my condo is not. Just over the last few weeks, several brown dying  branches have appeared. Our landscaper said all that needed to be done was to trim the branches and give it more water. What’s your thoughts?

A. Large dying branches in ash trees may be from a disease called ash decline. It can be from a lack of water but if the tree doesn’t look much better after three weeks when larger amounts of water are applied, then it is probably ash decline disease. There is no cure for ash decline and the tree should be replaced with a tree that is NOT an ash tree.  

Ash decline disease or drought. Water the area under the tree with a sprinkler for an hour once a week for three weeks and find out.

            Plant diseases don't happen all at once just like they don't happen all at once with diseases in humans or animals. The reason you see it on one tree is because it may be just beginning. Eventually if one tree has it, they will all get it whether that is in 10 years or 15 years, I don't know. Keep an eye on the others. Remove infected trees early.

Greening Up Brown Italian Cypress with Ironite?

Q. Does Ironite help Italian cypress if they are turning brown?

A. No. Ironite may help if the problem is an iron deficiency or the plants can't take up enough iron. Iron problems on plants turn yellow first before they turn brown and die. If the cause of the browning was from poor irrigation management and the soil staying too wet because of poor drainage, then Ironite will not do any good. The same is true for browning due to spider mites.

            By the way, Ironite only works if the soil is not too alkaline (pH above 7.6). Most of our desert soils are closer to 8.0 or higher. Mixing in lots of compost and adding water helps lower the soil pH close to the mid 7’s. But if the soil has been covered in rock for a few years then soil pH (alkalinity) will be close to 8 or above.

Grubs and Improved Landscapes Go Hand in Hand

Q. I have grubs in sections of my fescue lawn. They have been a problem in the past and they are again this summer. How do you prevent grubs from re-infesting a lawn each summer?

Grubs feeding and growing larger in the soil beneath a lawn. They will become "June bugs" in the summer.

A. Make sure the brown areas you see is damage due to grubs before you apply grub control products. Most brown spots on lawns during summer months are irrigation or disease related, not from grubs. Usually grub damage starts appearing early in the summer.

            Brown spots resulting from grub damage is probably the easiest to determine. In early summer, grab a handful of grass from the edge of a suspicious brown spot and lightly pull. If green grass is pulled up without roots on it, then your lawn probably has grubs. YouTube videos will show infested grass rolling back “like a carpet” but that’s only on sod forming grasses like Kentucky bluegrass. We have mostly tall fescue in our lawns which is a “bunch grass”. That makes identifying grub damage in our lawns different.

White grub larva just before it will become a "June beetle".

            If you are convinced that brown spots are due to grubs, then apply an insecticide for grub control to lawns in late spring. If you want to get a jump on controlling white grubs, apply the same insecticide to the lawn September through October.

Desert Horticulture Podcast: Why Mulch is Important for Desert Soil

Mulch is anything laid on the surface of the soil. Selecting the right mulch and using it can mean plant success or failure in the long run. Organic and inorganic mulch play different roles in landscapes. Rock mulch may or may not be the right thing to do with your landscape. Learn why on this episode of Desert Horticulture.