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Friday, February 17, 2023

Bitter Orange in Las Vegas

Q. I was so happy to see an article you recently wrote in the RJ concerning bitter orange trees.  I have one that was here when I bought my house 16 years ago.  It was in a patio pot at that time and I had it replanted, along with a Meyer Lemon, in the “alley” between my house and my neighbor.

Bitter orange tree planted in Las Vegas.

My lemon has been giving me fruit for the past approximately 8 years and about 30-35 lemons.  My orange tree has always produced flowers, but no fruit up until 2 years ago. I got about 25 nice sized oranges.  Last year I got flowers but Not A SINGLE fruit. Is this a tree that may “skip” a year in fruit production?  I have done nothing to these trees except fertilize with Arizona Best’s Citrus fertilizer Valentine’s Day, Memorial Day and Labor Day.

Myers lemon (not readers) planted in Las Vegas.

A. “Skipping” a year is called “alternate bearing” and occurs, usually, with older varieties of fruit trees like some almonds and apricots. Bitter orange, like most oranges, produces the majority of its flowers in the early spring. This is the same time we experience freezing weather. Your fruit loss could be because of freezes.

Did You See Flowers?

It is important to ask, “Are you sure you saw flowers in the spring and no fruit?” That’s an important consideration. If you did then it was a failure to set fruit. That is either because no pollinators were present (bees and other pollinators like flies and moths) or it froze several times in a row in the early spring.

No Flowers

If you did not see flowers in the spring, then it was because it never flowered. That could be because of some hard pruning that was done, and the tree is recovering, or too much fertilizer was applied too often. This is true particularly of high doses of nitrogen fertilizer such as ammonium sulfate (21-0-0). In either case, the tree grew so vigorously that it never flowered!

Fertilizer Applications

Normally one fertilizer application is all that is necessary, or two at the most. If two is applied, then apply half of your normal fertilizer application in the early spring and half right after harvest. If harvest is close to your early spring application time then apply fertilizer to citrus just before it gets hot in the early summer. Avoid making fertilizer applications when it is hot. In the case of citrus that might freeze, avoid fertilizer applications after July.

Tree Surrounded by Rock Mulch

Some citrus okay with rock mulch.

I noticed that the tree is surrounded by rock mulch. Yet it has good color. Citrus of all types don’t usually like rock mulch all that much. The first thing to go is dark  to medium green color in the leaves when it gets unhealthy. That’s why I was surprised with your tree. Maybe your choice of fertilizer helps.

Some citrus not okay with rock mulch. Use amended soil when planting and citrus fertilizer every year.

Citrus are from southeast Asia and China. They prefer to grow in soils with a higher organic content than most soils covered in rock. Along with your fertilizer application try raking back the rock at least three feet all around the tree and applying compost or wood chips to the top of the soil. Water it in and rake the rock back on top of it after it is watered. Do this about every year or every other year at the least. I think your bitter orange will like this type of soil better than soil covered in rock.

Pomello on our farm in the Philippines.

Properly Staking Trees and Other Plants in Desert Soil

 Q. I have a tree that was staked and now the wires used in staking it are starting to strangle the tree trunk.

Fairly common forgetfulness of homeowners and plant maintenance companies. Tree staking. Proper staking removes the stakes after one season of growth.

A. That's a common problem on large, staked trees planted in home landscapes. It's a gamble on the wind whether to stake or not to stake. I encourage people to stake nearly all plants. It's cheap insurance. On smaller 5-gallon plants (sometimes even 15-gallon shrubs) the small, square, green nursery stake found in the container may be adequate if cut loose from the plant, driven or pushed into the moist, solid ground beneath the plant. Retie the plant when you’re finished. Always have some half-inch, stretchable green nursery tape on hand. It's very useful.

Green stretchable nursery tape is used to tie one inch caliper bare root trees to a wooden stake.

The purpose of staking any plant is to keep new roots from being damaged during establishment. The movement of roots usually happens during strong winds. Planting in wet planting holes and amending the backfilled desert soil may get around the use of stakes with smaller plants. Use your judgement.

Wind blew over this cactus either because it was watered too often, watered too close to its center. If the soil surrounding the roots were moist, this cactus would find water further from its center and resist blow over.

Typically staking is only needed for one growing season and then removed. One growing season is all that is needed to establish plant roots in the surrounding soil and make the plant secure against wind. 

Some homeowners may think the reason for staking is to hold the tree upright. That's only partially true. On occasion more than one growing season of staking may be needed when planting trees grown too close to each other in wholesale or production nurseries. In cases like these, metal ties are loosened and then retightened at the end of each growing season to prevent “choking the trunk” as seen in your picture. Remember, plants grow in two dimensions; length AND girth. Sometimes excessively tall and weak plants must be pruned smaller to encourage new, stronger growth. 

The proper way to stake a tree is to allow the canopy and trunk of the tree to move but not it's roots. Movement of a tree’s trunk allows it to gain taper (become stronger) as it grows in size. Trunk taper may or may not be missing because of production nursery practices. Properly grown trees have a tapered trunk as you look at it from top to bottom.

Volunteer Planting Shrubs and Flowers

 Mark your calendars for March 4 beginning at 7 and 10 am. I am inviting you to an early volunteer opportunity to plant shrubs and flowers around the Nevada Garden Clubs Center on March 4 starting at 7am. This is your chance to rub shoulders with gardeners experienced with desert gardening and shop with local plant-minded vendors. This opportunity is located at 800 Twin Lakes Drive near Lorenzi Park, close to the Rancho and Washington area. There will be a “plant and seed exchange” starting at 10 am at the same location.

Some Plants are Damaged if Temperatures are Above Freezing

Some plants can get damaged at temperatures above freezing. Learn how and which ones.

Chilling damage occurs mostly to tropical fruit if temperatures are like a refrigerator.

Freezing Temperatures

This is the time of year, the second week of December, we normally experience the start of freezing temperatures. The likelihood of freezing temperatures increase through the winter. Sometimes freezing temperatures occur in November, as it did a few years ago, but that's rare and not “normal”. What I mean by “freezing temperatures” is plant damage that occurs anytime the air temperature drops below 32 degrees Fahrenheit (F). Those familiar with Celsius or centigrade, may realize this temperature is the same as 0 degrees on the Celsius scale.

What is Chilling Injury?

As a reference point, the temperature inside most refrigerators is set to around 40 degrees F, or 8 to 10 degrees above freezing; too cold for most tropical fruit and plants but not too cold for temperate fruit like apples and peaches. Chilling injury (plant damage that occurs because air temperatures are too cold for the plant but not yet freezing) is one reason many ripe tropical fruits, like tomatoes and (more obviously) bananas, should not be exposed to the 40-degree F temperatures of a refrigerator. All parts of tropical plants such as tomatoes and bougainvillea, experience “chilling injury” when temperatures drop a few degrees above freezing and may extend to 50+ degrees F. Chilling injury (as opposed to freeze or frost damage) occurs at different temperatures and depends on the plant.

Chilling Damage

Chilling injury damage to tropical and subtropical plants include small stem and leaf discoloration, leaf roll, poor growth, and susceptibility to some diseases like root or collar rot. Symptoms of chilling injury include a change in color such as yellowing or bronzing of leaves that ultimately result in leaf scorch or drop, the slowing or halting of growth, leaf drop, water-soaked patches in soft and semi-hard tissues, susceptibility to diseases, and wilting. Chilling injury is due to cooler or cold weather (above freezing) temperatures to tropical plants growing outside of, or close to, the fringes of their normal range. As a side note, I noticed leaf and stem discoloration (closer in color to leaf “bronzing”) in mesquite, palms, citrus and a wide range of plants growing at different temperature ranges.

Warm Season Vegetables Usually Have More Chilling Damage

Vegetables can exhibit chilling injury and freezing damage as well. So-called “warm season vegetables” such as tomatoes, peppers and eggplant can show chilling injury anytime the air temperature drops into the damaging temperature range I mentioned earlier. Cool season vegetables, on the other hand, may sail through the same temperatures, or lower, or require a crop cover when temperatures are below freezing. Vegetable varieties may differ in their chilling injury by a few degrees. The ‘Dragon’s Tongue’ variety of bush bean is more susceptible to collar rot (chilling injury) when grown in garden soil a few degrees cooler than other bush bean varieties.

Refrigerator Temperatures Result in Chilling Damage

Temperate fruit like apples and pomegranates, unlike tropical fruit like tomatoes and bananas, are not damaged at refrigerator temperatures (around 40 degrees) because fruit from these trees can handle these lower temperatures. The ideal storage temperature for these types of fruit is somewhere close to freezing (0 degrees F) and combined with high humidity. A high humidity slows water loss and helps delay some fruit from shriveling.

Freezer Temperatures Result in Freezing Damage

The freezer part of our refrigerator is set to around 32 degrees F, or about 10 degrees below the “refrigerator temperature.” Our nighttime winter temperature frequently drops to a “refrigerator temperature” range at night during the late fall, winter and early spring and occasionally into the “freezer temperature” range during the early morning hours of December, January and occasionally early February. When nighttime temperatures reach the “freezer range” is when we often times see plant damage or experience fruit loss, but we may not know it yet.

Open Flowers are All Subject to Some Type of Damage

Open flowers of any fruit (citrus, peach, apple and others) can’t handle temperatures below freezing (32 degrees F) even though most plants or trees might show no damage at all! When flowers are simply buds and not yet open, there is a small amount of freeze protection provided to the developing flower. This freeze protection starts disappearing as the flower buds mature into open flowers. As the flower begins opening, and the frost-sensitive ovary is surrounded by the freezing night air, is when we experience damage or fruit loss. Fruit loss due to a frozen flower ovary can happen in a few seconds. This is why sprinklers, ultimately resulting in applied water turning to ice on the flowers, are used in orchards to prevent freeze damage to flowers (ovary). The act of water freezing releases a small amount of heat that protect flower ovaries from death.

If you are curious if the ovary of a flower from your fruit tree was damaged during a freeze, pull the flower apart a few days after a suspected freeze and inspect the ovary for death. Ovaries that eventually turn into fruit will be robust and green. Dead flowers drop from the tree early or have a dull, water-soaked appearance if they are still attached. Just because the flower you inspected was “dead” doesn’t mean there will be no fruit produced at all. It takes about two or three weeks for all the flowers to open in spring flowering plants. Several consecutive light freezes in a row (or only one hard freeze) are needed to totally wipe out a crop of fruit from a mature tree.

 There is a temperature difference between the freezing death of open flowers and the freezing damage or death of the plant or tree. For citrus this difference can range from the same temperature as flower death (32 degrees F; limes and true lemons) to lower temperatures (mid 20 degrees F; Myer lemon, grapefruit, and kumquat). Much of this depends on how many minutes or hours a killing freeze lasts and at what temperature.

Temperature, and duration of that temperature, are what is critical. With open flowers, freezing temperatures are needed for just a minute. With plant or tree death, the same temperature is needed for a longer time period. With some fruit trees (such as citrus), the temperature difference between flower and tree death can be small (0 to 7 degrees). In other fruit trees (such as apples, pear, peach and apricot) it can be much greater (20 degrees or more).

What to do about freezing temperatures and fruit or plant loss? Track and use weather station apps during times when freezing temperatures might occur. Buy a recording thermometer for your backyard and hang it in your important trees. If you are into growing vegetables, use a soil thermometer to judge when to precisely plant.

Move fruit trees to a new location. If your fruit trees are less than three to four years old, now is the time of year to move them. South and West-facing sides of walls and buildings are tough to grow plants because of the heat they reflect. Some citrus are in landscape “wind tunnels” that remove flowers during strong winds. North and east sides of buildings and walls as well as backyards have a gentler environment. In cooler, gentler areas of the landscape expect flowering to be two to three weeks later. Group plants together so they can share water, fertilizer, and protect each other. If they can't be grown together, consider constructing wind barriers.

Try kumquats which are a cold hardy, subtropical citrus trees. The small fruit can be freshly harvested and eaten from the tree but still gives you that citrus “kick”. Kumquat flowers several times during the summer instead of just once and yet is small enough to grow in a container. Flowering more than once during a single growing season increases your chances of having a successful crop if you have late or multiple freezes.

Grow fruit trees that flower continuously. Pomegranate, fig and jujube are temperate cold and heat tolerant fruit trees that flower continuously through the growing season.

Always group plants and fruit trees together. Improve the soil at the time of planting and every couple of years. The water, soil improvement and shade that they provide and share is a big benefit to them when grown in the desert.

Yellow Leaves on Potted Myer Lemon

Q.  I have a Myers lemon tree in a pot on a south facing patio. The wall near it faces east and there was a large pine tree out front so it receives shade in the afternoon. There are quite a few yellow leaves that just appeared. All the new fruit has turned black. It seems to me that maybe I just need to replace this tree. The lime tree is doing very well in a similar location.

A. The picture you sent to me shows a Myer lemon with ready to harvest fruit being grown in a small container with smaller plants growing around its base. Meyer lemon typically flowers sometime in January and February. The fruit can be harvested starting about now (December) with this harvest, finished by January, encourages new flower development for next year’s production.

Producing flowers and then fruit in midfall is early for Meyer lemon. Early flower development can be a sign that it is under some sort of stress. Certainly it's not normal for this type of tree at this time of year.

            All fruit trees and vegetables need a minimum of six hours of full direct sunlight. 8 hours is even better. In home landscapes the best sunlight for it in our hot climate in the summer months is during the cooler morning hours. Partial shade may be pleasant for people sitting on the patio but not for many plants that produce fruit or vegetables.

If shade is present during most sunlight hours, then I would recommend an ornamental plant for that spot with variegated or colorful leaves, not a flowering or a fruit-producing plant. A non-flowering ornamental handles shade better than a flowering plant, whether those flowers produce fruit or not.

Don't Plant Annuals at the Base of Perennial Trees

            Secondly, and perhaps more importantly, are the smaller plants demand for frequent watering compared to the tree. Growing a shallow-rooted plant or plants at the base of a deeper-rooted plant is a big “no-no” regarding how often water is applied. Shallow-rooted plants “signal” they need water applied more often than deeper-rooted plants, so they get water applied more often than the watering frequency needed for deeper-rooted plant needs.

This type of watering can suffocate the roots of a deeper-rooted plant. Watering a deeper-rooted plant too often can produce leaf drop, flower drop, fruit blackening, and a tree that's “loose in the soil”. Trees that develop “collar rot disease need to be staked after just a few years of growth. Does that sound like your fruit tree?

            I would replace this tree with a plant that requires moderate to low levels of sunlight. If you want to grow other plants along with it, select plants with a similar rooting depth and need for applied water.

Pecans With Black Spots and Bitter Meat in Southern Nevada

Q. I had two pecan trees that are now 25 years old. One variety has round nuts and the other one has oblong nuts. This is the first year in 25 years they have produced nuts that have black spots and are bitter tasting but the outside of the nut looks normal. Any idea what the problem might be?

Pecan scab. Picture from Texas A and M University.

A. Pecan nut problems are hard to diagnose. The nuts themselves can be bitter if some of the husk is attached to the nut. But yours sounds like a disease issue to me. Perhaps it was our wet early summer and spring that created the problem.

The most common disease of pecans is scab. When it is a wet spring, after a rain, it is wise to spray the trees in March with a fungicide such as Bordeaux or copper sulfate. If it rains again, spray it again after the rain has stopped. The problem is spraying these trees top to bottom since there are no systemic fungicides that can be applied to the soil and taken up by the roots. The lesions on the outside surface of the shell this disease produces are difficult to see and does produce an “off flavor” once inside the meat.

I must guess a little bit, but the varieties popular about 25 years ago in the West were oblong nut varieties called “Western Schley”, “Mahan”, “Wichita”, “Mohawk”, and “Cheyenne”. The older and round nut varieties were either “Burkett” or possibly “Choctaw”. The reason I mention it is because there are probably well over a hundred varieties of pecan. The more recent hybrids are smaller, produce nuts sooner, less likely to bear nuts every other year (alternate bearing), and don’t need a pollinator tree. Also “Choctaw” and “Cheyenne” varieties were considered “resistant “to this disease.

Even though pecan trees can handle our summer heat and poor soils, I don't recommend them for our area because of their size and water use. Pecan trees can get big, growing 60 to 100 feet tall and 30 to 50 feet wide, and have no semi-dwarf or dwarf varieties that I know. Their size dictate they use a lot of water. They do have a sizeable tap root so they possibly could be used where there is shallow underground water.

'Desert Museum' Palo Verde Damaged by Wind

Q. I have a Desert Museum Palo Verde that was damaged during a windstorm. One of the branches blew off and damaged the trunk. It is an eyesore. Should I replace it?

Palo verde is a rather soft tree particularly if you are in a hurry and want to grow it fast. Watering it like a mesic tree will speed its growth but could increase its potential for damage during strong winds.

A. I would let the tree heal on its own but help it along its way. Healing takes two to three years if the tree is kept in good health. To do that, clean up the wound and apply management practices that encourage it to heal. 

Sealing paints are a gimmick and don't help the tree heal. In fact it can do just the opposite and prevent rapid healing.

Don't use any paint or “tree healer” as this was proven ineffective in past research and could actually slow the healing process. If you do paint the damaged area, use latex water-based paint. If there are any “splinters” resulting from the damage, remove them with a sanitized knife. Make the damage, and healthy areas surrounding it, as smooth as possible so the healing is faster and pleasant to look at.

With that same knife remove the outer bark so that the edge is smooth and clean, and the damaged area is shaped like a vertical football. The damaged area will “compartmentalize” and the tree will “roll” over the area as it heals over the next couple of years. When the tree starts to grow this spring, make sure it gets adequate amounts of water and fertilizer. Good health practices help the tree to heal faster.

To reattach or repair a limb split, or otherwise damaged area from a tree during a windstorm, is usually a lost cause. If done successfully the limb must be reattached, or repaired, within minutes or even seconds after it is severed or broken. Time is very important so that the damaged area doesn’t “dry out” before it is repaired.

Strawberry Guava for Las Vegas?

Q. I am interested in growing strawberry guava in Southwest Las Vegas and wish to know if these are good choices. Can you tell me what fruit and evergreen tree varieties have the best chance to survive in our desert?

Strawberry guava is a guava with red fruit. It is cold or winter tender and should only be grown on the east side of a house or tall wall. The soil MUST be amended with compost.  It requires a lot of water (mesic) and can grow over ten feet tall. Here it is growing at our farm in the Philippines where it is warmer. Strawberry guava doesn't taste like strawberries.

A. Our desert can be a place to grow strawberry guava except for our cold winters and occasional snowfall. The fruit grows on new growth from a small tree, 10 to 20 feet tall. If they are kept warm or from freezing and planted in a part of the landscape that gets afternoon shade, then strawberry guava will work here. 

During the very low winters of 1989 to 1990 it got from 10 to 15F but those are 25-to-50-year lows. So short term, temperatures of 25F or below is expected occasionally. Fully grown, they will survive freezing temperatures to about 25F for short periods of time.

How to Grow It Here

Its not easy or cheap. My suggestion, if you plan to grow them here, is to pick a non-windy place (windy locations make temperatures colder in my opinion) in your landscape. This protected location should get at least six hours of direct sunlight in the morning. Protect them from the wind with a constructed wind barrier. Not a solid wall. Solid walls create “dust devils”. Pick a location that is either on the east side or north side of a building or wall, not hotter locations found on the west or south sides.  Plant them at least five feet from a wall or building.

Make sure the planting hole is about 3 to 4 feet wide and dug as deep as the roots. Amend the soil with compost or use composted soil when planting. Make sure the soil is wet, not dry. Plant in a hurry. Cover the soil with a 3-to-4-inch layer of wood chips when finished. Stake the tree after planting. Protect it from rabbits or other vermin if they are seen. Applied water should wet the soil to 18 inches deep to at least half the area under the tree canopy as it gets bigger.

Avoid planting seeded types but instead pick pink or red varieties like ‘Homestead’, ‘Barbie Pink’, ‘Hong Kong Pink’, ‘Blitch’ and varieties recommended by the University of Florida that have proven successful there. Green varieties are picked before they are ripe and red or pink varieties are picked after they ripen. Guava is a climacteric fruit so it will ripen further after the fruit is hard but near ripe.

Star Jasmine Needs Sun and Watered Like a Shrub

Q. I am hoping you can tell me what is wrong with my "star jasmine". These plants are approximately twenty years old. The wall they are growing on is north facing. I have pulled the rock mulch away from the base. I mix in compost to each plant every spring when I fertilize. Could it be the irrigation is too close to the trunk?

Star jasmine is from the area of Japan. The great deserts of Japan...not!!! It is not a xeric plant and so it can get yellow, iron chlorosis, in rock. Plant it with compost in the soil and build up the organic content.

A. Without looking at the pictures I was expecting them to be yellow. That’s usually what happens to star jasmine in rock landscapes. Your addition of compost to the soil is keeping them green and healthy.

Bare wooden stems can sometimes happen when it is in poor health or covered with shady growth on top.

Perhaps Watering too Often

Bare stems on older growth can be a natural occurrence. I don’t think it is in your case. It is possible if the water applied is too close to the stems AND it is being applied too often then you can end up with bare stems. It is best if the water is applied at 12 to 18 inches from the trunk (stems, base) of the vine.

Water, when it hits the soil, spreads out. In soils that are very sandy then this distance might be 12 inches from where it is applied. If the soil has a small amount of clay in it then the spread is about 18 inches from where it is applied. In soil with lots of clay (most of the soils in Las Vegas do not have that much clay) then water can spread out from where it was applied from 4 to 6 feet. A happy medium is 12 to 18 inches from the stems or trunk.

Be careful of applying water too often. It can keep the soil wet too long. This can result in leaf drop followed by bare stems. It is always best on plants that have deeper roots (like your jasmine vine) to apply water less often. Vines like star jasmine are deeper-rooted, like medium sized shrubs. Water should wet the soil 12 to 18 inches deep each time is applied. Water your vines like they are medium sized shrubs.

What to Do?

What can you do with bare stems? Cut them back no closer than three or four inches and they will send out “suckers” and those suckers will fill in open spaces if the vine is alive. You may have to cut alot of stems back and start over if it is bad.

Rabbit Chewing Damage to Peach

Q. I planted a peach tree late last winter but before I could protect it the rabbits began chewing on it a bit, not all the way around just a few spots. I’m not sure if borers have gotten to it. Do you think it can be saved or is it time to pull it out?

Rabbit damage to a peach tree. Rabbits love to eat fruit trees in the winter when not much else is around to eat. If you fear rabbit damage, use one inch hexagonal fencing to protect them when they are young.

A. Most trees, including fruit trees, can lose about half of their bark by chewing and still survive. If it were me I would tally up all of the damage and if this damage is less than 50% then it should be fine. You might lose some branches that are severely damaged but the majority should survive. 

A cylinder of 24 inch wide, one inch hexagonal chicken wire is usually good enough protection for fruit trees from rabbits.

Protect the rest of the tree from vermin damage and don't worry about it too much. The damage will heal on its own. If you want the tree to recover from damage faster, make sure it is getting enough water and fertilize it at least once each spring.

Best Iron to Use is EDDHA Chelated Iron

Q. I’m starting to think about the springtime approaching and the need for fertilizing. Do you have an “iron Fertilizer” you recommend? We added the compost you suggested but I want to make sure we are on top of the iron needs of our plants.

Iron chelate fertilizer that works in all soils. Its a bit more expensive but it is a guarantee. The others will work most of the time.

A. The iron chelate I like to use is a little bit more expensive. The reason I recommend it is because of its stability in both highly alkaline and highly acidic soils. It works regardless of the soil or its alkalinity (soil pH). I consider it cheap insurance.

Severe iron chlorosis on a peach seedling. Chlorosis is any yellowing leaving behind green veins. Iron chlorosis occurs all summer long but it is on new growth. Iron should be applied sometime in the early or mid spring, before April in our climate.

The chelate I like to use is EDDHA iron chelate. It comes under several names but as long as the iron is bound to the EDDHA chelate then it is what I recommend. Other types of chelates and iron fertilizers stop working in highly alkaline soils.

This is another iron chelate fertilizer called EDTA. It works in most soils. It is the most common form of chelated iron fertilizers for plants because its more available and cheaper.

            If you are adding compost to compost amended soil then any chelate or iron fertilizer will probably work whether it is iron sulfate, brake filings, or iron chelates such as EDTA or DTPA This is because soils that have compost added to them usually are not strongly alkaline. The compost additions, along with water, usually lowers the alkalinity of the soil.

The chelated iron I prefer, iron EDDHA, works over all of the different soil pH or alkalinity.

            Any iron fertilizer or chelate MUST be applied and mixed with the soil in the early spring (sometime soon after February 1 in our Las Vegas climate). Soil applications get less effective as the growth begins stopping. By mid to late summer you must switch to iron fertilizers applied as a liquid to the leaves for acceptable results. This usually requires several applications to shrub leaves. Iron fertilizers applied wet to the leaves (foliar applications of iron) are not as effective and may need to be applied to the leaves of trees and shrubs several times to work.

How to Get Rid of Bermudagrass Weeds in a Tall Fescue Lawn

Q. How can I get rid of bermudagrass now, growing in a tall fescue lawn.

Bermudagrass invasion of tall fescue due to irrigation and mowing height. Keep mowing height at least 2 inches for tall fescue and keep it full and lush.

A. The best way to get rid of it in fescue is to cut it out if possible and then seed the bare spots after the Bermudagrass has had time to die. The best time to do this would be about April or May when Bermudagrass is starting to green up. You've got to kill the Bermudagrass when its alive, which starts growing in late spring, and seed the bare areas after all the grass in that area dies.

That's tricky because Bermudagrass is a warm season grass and doesn't start growing until about mid-March or early April. It’s easier to control fescue growing in a Bermudagrass lawn while the bermudagrass is dormant (sleeping and dead looking). The fescue in the lawn is cool season so you can begin seeding when it's cooler. But bermudagrass is warm season so it doesn't "wake up and start growing" until late spring.

If you want to try that then I would recommend spraying Roundup (its the only systemic grass killer available) in spots where the Bermudagrass is growing in the late spring and wait about a week. Don't use Roundup combined with any other weed killer. Just plain old Roundup. The systemic Roundup translocates and kills some of the roots of bermudagrass. 

First, cut the grass in the Roundup-applied area shorter and seed directly into those spots. Because Roundup is systemic and slow acting it will continue to kill the bermudagrass. The label on Roundup prevents you from seeding any sooner than this. You should start seeing the fescue pop up from seed in about 7 to 10 days as the grass in those spots continues dying.

What to Do?

1. Mow the area shorter.

2. Spray Roundup over the area without any other weed killers in it. Just plain old Round-up. The grass wont die for 2 to 3 weeks. 

3. After one week, seed a high value tall fescue seed in the same area. The grass you sprayed will look like it is alive but it is dying.

I would mow the area shorter, somewhere between a half to an inch tall, and apply ammonium sulfate (21-0-0) in early March. The Bermudagrass likes warm weather, as well as nitrogen fertilizer, and it will start turning green a couple of weeks earlier than when it is taller. Use a high-quality tall fescue variety to seed in those spots. The grass will not be dead yet but it's dying, and you have to trust that it's dying. As the new fescue seed is coming up you will see sprayed areas start to die or turn brown.

You can safely seed into Roundup-applied areas 7 to 10 days after the spraying has been done. The tall fescue and Bermuda does not look dead yet, but they are dying. You can't start killing Bermudagrass until after it starts getting green in the spring.

Preventing Bermudagrass Invasion

In the future keep your mowing height between two and three inches. Keep the lawn thick to choke out any invading Bermuda grass. To do this apply fertilizer to fescue lawns at least 4 times per year; Valentine's Day, Labor Day, Memorial Day, and Halloween. The fertilizer to use is a 21-7-14, between half to 3/4 of the bag rate if you are returning the clippings to the grass (not bagging). The rate on the bag may be too much fertilizer. Don't give the edges of your lawn of bevel cut because it encourages in Bermudagrass invasion. Instead use a steel edger perpendicular to the edge of the lawn.

How to Prune Clematis Vine

Q. How to prune clematis vine in North Las Vegas?

Always prune "pretty plants" immediately after they finish flowering. If they flower most season long, then prune them in the winter. This picture is from another reader.

A. To get a “how” it is best to send some pictures. Without pictures I can tell you “when”. Clematis vine should flower late in the spring and then again in the fall if you are lucky. 

There are multiple ways to prune it depending on what you've got. Clematis is basically a flowering woody vine that can be pruned as if it were a shrub. The flowers grow on older wood and, depending on the variety, can flower anytime from spring until fall. If the vine or shrub flowers all season long, then winter is the best time to prune.

Always prune flowering vines and shrubs just after they finish flowering. You are okay pruning now because the winter has interrupted the flowering.

Did you know there is a “native” clematis? It is not as spectacular when it flowers, but it is a native and so it can handle less frequent watering. It is still a clematis!

Brown Leaf Tips on Strappy Leafed Plants

Q. What causes the brown tips on some strappy-leaved plants like iris or agapanthus? Should I cut it off?

Tried to find some leaf tip burn or leaf scorch on narrow leafed plants like Mondo grass or agapanthus. No luck. It is always the same. Not enough water is applied, the soil is not improved, salty soil or water, or it was planted in a hot location. In the case of Mondo grass, it should not be planted here. The humidity is just too low for it. 

A. You didn't tell me which plant you're concerned about because some plants are less tolerant of certain location than others. This browning of the leaf tips is called plain old “leaf scorch”. It can be caused for lots of reasons; sun is too bright, low humidity, windy locations, poor periodic soil amendments, watering too frequently, salty soil or irrigation water, or watering not often enough.

            For instance, Mondo grass (it is a form of Liriope muscari or grape muscari) is a small plant with “strappy leaves” with lots of different common names like border grass, monkey grass, grape hyacinth, and others. It gets leaf scorch in the desert in ALL locations. That’s the way it looks in the desert. When in doubt, call it by its scientific name (or Latin name) and understand where it is from.

            Getting back to your plant, do what the gardeners in the hotels do to indoor plants. They cut the leaf scorch off and make the ends of the leaves resemble others. This makes the plant leaves look more “natural” to passerby’s who just glance at it or pay no attention. If most of the remaining leaves are pointed, then cut it off in a point. If you end up not liking the look, remove the entire leaf by cutting it off at its base and hiding the cut.

            I know I sound like a broken record but, when pruning, always sanitize the blades with at least 70% alcohol when starting.

            Consider moving the plant to a more hospitable location. If it looks like the leaves are scorching, then move it to a shadier spot. If that doesn’t work and you remove it, then lesson learned. Consider it part of your education. Learn the name of the plant and buy something different.

            Remember, plants that have showy flowers need more light than those that don’t conspicuously flower. If you planted a nonflowering plant and it was planted at the lowest level of light available, then the same plant will not work in that spot. Either that or more light needs to be made available.

Bitter Orange a Good Choice for Las Vegas But....

Q. Is it possible to grow sour or bitter orange in Vegas? It’s becoming almost impossible to find at the local markets and we use it in so many recipes. I was curious if that was something that might grow here? When should I plant it?

Bitter orange, sometimes called trifoliate orange, is a good choice for colder climates like Las Vegas where it oftentimes freezes.

A. They aren’t very popular here. I understand why you might want to grow them. We are talking about Citrus aurentium. They are used as a landscape highway plant or landscape hedge in the Phoenix area where it’s warmer during the winter. Here they are mostly used as a low temperature rootstock for citrus when shipped to our area by wholesale nurseries. Trifoliate orange is used primarily as a freeze tolerant rootstock for our area, but sour orange is also used.

Sour orange is used as a rootstock for citrus needing to be cold hardy. If the top of a citrus dies due to freezing temperatures, at least the rootstock will sprout and grow after the top freezes.

I don't have the information on their low temperature tolerance for the winter, but I think it’s around 20° F so it would be a good choice for planting in the Las Vegas area. Meyer lemon and kumquat, two more commonly grown citrus here, will handle freezing temperatures to about 24-25° F. once established. In protected backyards Meyer lemon, grapefruit, and kumquat survive most of our winters. So, my guess a fifteen-foot sour orange will be at least reach those temperatures, if not a bit lower.

This tree should start flowering in about year four to six. You will still lose fruit due to early spring freezes combined with open flowers in some landscapes depending on its exposure to early spring freezes and wind. But the tree itself should survive our annual fluctuating freezing temperatures for about 25 years or more.

Remember ALL citrus are from China and parts of southeast Asia. This means the desert soil needs to be amended at the time of planting, and periodically adding amendments to the soil. No citrus are xeric so they will need about the same amount of water as regular fruit trees of a similar size, about 4 to five feet of water under applied under its canopy in one year.

Just for your information bitter orange does get a deadly disease occasionally but it's usually not prevalent in non-orchard citrus areas so you should be all right. Buy the tree smaller and protect the tree from sun damage through shading itself or providing it shade while it gets established. Buy a tree that is shrublike.

You won’t find it locally. It is not that popular as a tree on its own. I think you will have to order it online. Places outside of the desert southwest don’t have to worry much about sun damage to the trunk so it is limbed up higher into a tree. For this reason, you want to buy it grown into as much of a bush as possible. Limb it up later when it gets older and acclimated to our desert. The best places to order it are from Arizona nurseries such as Whitfill or Greenfield if they will ship it to you. Both are in the Phoenix area.

Plant it when temperatures are cool, but spring planting is best in the case of citrus. Because of digging and availability, most nurseries sell bareroot trees in the spring. Bareroot trees need to be planted as early in the spring as possible. Potted or container trees can be bought anytime but planting them is always best in the spring. If it were totally freeze tolerant, or you were sure it will not get extremely cold this winter and you can find it available, then fall planting is always best.

Root Rot on Pines?

 Q. I have several very large pine trees that have been in ground since 2002. Due to heavy winds, one was felled, and the trunk broke. Upon inspection, it looked like root rot! Can you advise how much water these trees need in winter and summer. I want to be sure the see does not happen to others.

A. Make sure the trees have water applied to a wide area, equal to about half the spread of their canopies. Tree roots follow applied water in the desert. Pine trees are relatively deep rooted. For this reason, apply water to them deeply. However, if the soil is hard, and the water applied too rapidly, the water may begin puddling and the tree can blow over easily. Watering plants in the desert tells them where you want their roots to grow.

The roots of any large tree near a wall is a "recipe for disaster". This large pine tree eventually heaved this wall when the roots "grew looking for water". The roots heaved the wall.

The other problem is watering. If they are given small drinks of water frequently (think planting in lawns) they develop roots that are shallow and will not hold them upright during strong winds. 

When planting pine trees it may be a good idea to plant other smaller shrubs around its canopy. Pine tree roots will grow where the shrubs area as well and help support it. Unless you know what you are doing, it may be a bad idea to have a pine tree planted all by itself surrounded by desert soil that is not irrigated. These trees will blow over. 

Place plants around the pine tree that are throughout its canopy as it grows larger. Putting irrigated shrubs around pine trees helps the pine tree roots to grow into the surrounding soil and become more firmly anchored. It is not something mystical about the surrounding plants. It is because these plants are irrigated, and they share water with the pine trees.

When to Stop Cutting Asparagus

Q. When should you stop cutting asparagus? We've had a good crop in the past but seem to have quit harvesting too soon in prior years so want to go as long as possible. We enjoy eating it!

Asparagus spear called 'Purple Passion' harvested

A. The textbook answer is 6 to 8 weeks of cutting and then you should let it go and rebuild its crowns beneath the soil for next year’s harvest. That information was given back when asparagus spears were thought to be marketable only if they were the diameter of your thumb. That’s changed and now we see asparagus sold much smaller in diameter than that and marketed as such.

Asparagus spears will produce spears large in diameter at first but after the crowns get exhausted from production the spears will get smaller and smaller in diameter. It is up to you when to stop harvesting them. But in the older days, asparagus spears were harvested until the spears got smaller in diameter and smaller.

The other answer is to continue to harvest until you see a noticeable decrease in the diameter size of the spears. When they start to get too small for harvesting (don’t just look at one spear but take an average), stop and let the roots and crowns of asparagus rebuild themselves.

            Asparagus will rebuild itself better if you can provide some nutrients as the crowns are putting away storage for next year. After harvesting, apply at least an inch of rich compost or you can also use manure.

In late December or early January the asparagus bed is fertilized with either manure or a rich compost. Sometimes a fertilizer is required if no manure or rich compost is available.

            The crowns should be 6 to 10 inches deep depending on the soil so laying manure on top of these areas should cause no problems. (Some manure is high in salts.) Planting the crowns deep makes sure the spears don’t come up too early. Make sure you water it after planting. After planting don’t water too often because the crowns are deep. Apply water on a similar irrigation cycle as fruit trees. The roots and crowns should have water available at the same depth.

Asparagus crowns are planted 8 to 10 inches deep. In retrospect, I would have used more compost when planting and made the planting area darker...more organics in the soil.

Thursday, December 15, 2022

How to Water Sago Palm (Cycad) Once Each Week in the Winter

Q. Now that our irrigation is only allowed for 1 day, I was wondering if once a week is sufficient watering for my small sago palm. Should I hand water it on other days?

Not the readers sago palm (cycad) but it is small! It is in a container so it is more difficult to water than one planted in the ground. The soil in the container is more limited in size than one planted in the ground.

A. Hard to say. Depends on how much water your soil around the sago palm holds, where the drip emitters for it are located and the side of the house it’s on.

Hard to believe this cycad, or sago palm, is growing in Las Vegas. It was situated in the right location with the right care.

           Ideally the drip emitters are located between 12 to 18 inches from the trunk. For large sago palms I would suggest three emitters spaced in a triangle. Run the irrigation system long enough to water 12 to 18 inches deep. you can measure that with something long skinny and hard like a piece of rebar. If the sago palm is smaller, it may need only two emitters to wet the soil to the same depth. Smaller plants don't use as much water, but the system needs to run just as long.

Hard to accept this is the same plant as the one above. But this one is located in the heat of the sun and growing in poor soils.

           Plants on the south and west sides of the house or wall use more water faster than those on the east and north sides. A deep watering once a week should be all that is necessary for them in most soils and locations except the hottest.