August is Early for Chinese Pistache Fall Color in Las Vegas

Q. My Chinese Pistache was planted in my xeriscape front yard almost 4 years ago. Overall, I’d say it’s doing fine.  One thing puzzling is that the leaves started changing to “fall colors” around the beginning of August.  I don’t remember when it changed colors last or previous years but I think that’s a bit soon.  Again, the tree looks healthy to me but I thought I’d check with you to see if I should be concerned.

A. I agree, August is early in our climate unless there had been some unusually cold weather. Early fall color can be a sign of plant stress and this would be followed by unusually early leaf drop. The usual reason for this type of stress is either a lack of water or possibly watering too often.

Pistache with fall color.

            When watering, give the plant a lot of water all at once so the water drains to a depth of 2 feet, wetting all the roots. This will require that there are enough drip emitters and they deliver enough water if you are using drip.

            Chinese Pistache trees can get large, 40 feet, and the larger they get the more water they will need. Increase the amount of water they receive by adding more emitters every few years. It also helps if this tree has other plants growing around it that are receiving water.

            Do not water this tree daily. That is a big no-no. Watering deep, twice a week, would be plenty.

            Chinese Pistache will survive lawns but the soil under lawns is usually much better than the soil under rock mulch. When they are growing in lawns, this soil can be much more forgiving than the soil under a rock mulch that is getting watered too often.

            Chinese Pistache typically does not have a lot of insect or disease problems in our area so I would tend to think that this would not be the case unless of course you are watering frequently. This will cause big problems for this tree in the future.

Lawn Problems Basically Boil down to Three Types

Q. See if you can figure out what's happening to our lawn. It is dying. I'm very bad with technology so I'll have to send each picture in separate emails.

A. First of all, you did a very good job with the pictures. They all came through just fine.

Dying lawn from unidentified causes.

It is very difficult to determine a problem with the lawn from pictures. Lawn problems basically boil down to three types; disease, irrigation or insect problems. Sometimes it can be a combination of these.

            The pictures make me lean towards a disease problem. The first picture you sent had a combination of two grasses in it; tall fescue and there was a patch of what I think was ryegrass in the center of the picture. In that picture, the problem only affected the tall fescue and not the ryegrass.

The lawn has a color difference that you can see which is actually due to a difference in "texture" more than color. Different grasses have different "textures" due to the reflection of light on the leaf surface. This textural difference is a good indicator that more than one type of grass is present in "patches" and not mixed together.

            Lawns dying because of irrigation usually die in a specific pattern related to the irrigation sprinkler heads. Sometimes this pattern can be in between irrigation sprinkler heads and sometimes the pattern can be close to irrigation sprinkler heads. It depends on a number of factors including the nozzles that are used, operating pressure of the system and the design of the system.

            Homeowners that design their own irrigation system usually tell me it's not due to design because they "did it themselves". Good irrigation design is not something that most people can do. It is much more complicated than people realize.

Not the lawn in question. Grass suffering from drought will grass near the damaged area with a darker appearance than the rest of the lawn. This is because blades of grass either "roll" or "fold" in response to a lack of water and cause this darker appearance during times of drought.

            There are many landscape contractors who are skilled at irrigation design or they purchase the materials they need from companies that provide for them a professional irrigation design. Fly-by-nighters will not be skilled in this area.

            Poor irrigation coverage or management will contribute to disease problems and lawns. It is imperative that a good looking lawn has an irrigation system that is designed and installed by professionals.

            Poor irrigation management will contribute to disease problems. Never irrigate a lawn if there is more than three hours of darkness after the irrigation has been completed. A wet lawn sitting in darkness for more than four or five hours when temperatures are above 80° F has a very high probability of becoming diseased. In other words, "Never put a lawn to bed wet."

            I was not in town in September and I understand there was a long period of wet weather and warm temperatures. When I heard this, I was thinking this was an ideal condition for disease development in lawns.

            Disease problems may develop in a pattern or they may not. It really depends on the disease and to a lesser degree the management decisions applied to the lawn. Judging from the pictures you sent and what I have seen historically here I lean more towards a disease problem.

Diseases in lawns frequently develop some type of "pattern". Not always but it can be a good indicator that a disease is at work.

            What to do? Diseases will run their course until there is a change in the weather or management practices. If this disease problem began during September rains then the lowering of temperatures and low humidity stopped the disease from spreading further. It will probably do little good to apply any kind of fungicide now.

            We are getting to the tail end of the lawn planting season. I would make a decision to either replant the lawn from seed or sod but you should get it done by the middle of November at the latest.

            If you decide to re-plant from seed then mow the areas that are dead as short as possible and rake or power rake these areas until you see bare soil. Seed these areas with a good quality lawn grass. If your lawn is predominantly tall fescue, then select a good tall fescue blend and don't use a cheap one. If you are going to lay sod in these dead areas, rent a sod cutter and lay some new sod in these spots.

Backyard Wildlife in Las Vegas

Here are some pictures sent to me by readers of some wildlife they saw in their backyards recently. Remember the fires that occurred in the Mount Charleston area a while back. Water is a great way to attract all types of wildlife into your yard.

Bird at birdbath identified as Cooper's Hawk

One of the readers reported to me that she saw this Cooper's Hawk take out two pigeons.


Wikipedia on Cooper's Hawk
Wikipedia on great horned owl

Bird at birdbath identified as horned owl

Oleander Toxicity Probably Not A Problem for Vegetables When Composted

Q. I read you said recently that oleanders can be composted. Just for clarification, can they be composted for vegetable gardens since they are toxic?

A. Yes! They can be used for mulching and composting! Mulching is when the plant is chopped up into small pieces and laid on the soil surface. Composting is the controlled rotting of the plant so that it can be mixed in the soil as an amendment and fertilizer.

            There is contradictory information circulating on the Internet about the safety of oleander but the study below strongly suggests that there is no problem with it when it is composted and used for growing vegetables. They do warn that it is not safe to eat the compost (why someone or an animal would do that I don't know). It is also not a problem to compost eucalyptus as well.

Composting Oleander Recommendations

            The smoke when burning oleander is a problem if inhaled. Although about 60% of our landscape plants are poisonous to some degree, oleander is one of the most toxic along with Datura spp. (a.k.a. Jimson Weed, Angel’s Trumpet, Thorn Apple), Nightshade, Castor Bean (Rosary Bead), Rhubarb, Moonseed, Lantana, Yew and Wisteria.

Clean up Debris to Reduce Skeletonizer Populations

Q. Although I was able to control the grape leaf skeletonizer all summer, I came back from a three week trip with 99% of the leaves stripped and dried up.  The grapes were picked in August and September. Should I still treat the vines with BT or just forget it since it is October and the leaves

would have soon turned brown anyway?

Skeletonizer feeding on the bottom side of grape leaves.

A. I would just let it go at this point. The only thing I worry about a little bit is regrowth (new leaves produced) because the temperatures are still warm. Regrowth will drain stored food reserves from inside the plant.

            These reserves are used for next year’s production but there should be plenty of “food” left even if it regrows this fall. I would not worry about it if that happens.

            Make sure you cleanup the leaves at the base of the plants. This is where the pupal stage (cocoon) will overwinter and if you do not cleanup this debris the attack on the plants next year will be earlier and more intense. The adults are winged moths so they will move from neighbor’s vines to neighbor’s vines. 

Curled Leaves on Pomegranate

Q. Our pomegranate tree has been planted for 5 years. We've had some fruit the past 2 years.  Lots more this year. I just spotted one already split with critters on it. The leaves look shriveled. Gave it fruit tree fertilizer and an extra watering. Any other suggestions would really be appreciated.

A. I looked at the pictures you sent to me and your pomegranate does not seem to be very full. The reasons they tree may not have filled out is because of the shade or not enough light during the day, not getting enough water or not fertilizing at the beginning of the growing year.

            Don’t worry about the curled leaves. This can be fairly common on pomegranate.

            They like to be deep watered just like any other landscape tree or shrub or fruit tree and watered about as often as well. If you want good production, don't treat them like a cactus. So in short, fertilize the tree in late January or February and start weekly irrigations the first week of

February.

            I would construct the basin around the tree about 3 feet in diameter and 3 to 4 inches deep and fill the basin each time you irrigate. If you are to use drip irrigation, and they will perform good on drip irrigation if they're getting enough water, then make sure you have about four emitters and you run them long enough to deliver the water they need.

            The critters you see are leaf footed plant bugs and normally soap and water sprays would be enough to knock them back but you'll have to apply it weekly to the undersides of the leaves and all over the foliage.

            Pyrethrins sprays will also work on them. And if you are hard-core, the insecticide is Sevin will kill him but don't spray when the plant is in flower and spray very early in the morning or at dusk when bees are not present. I hope this helps.

What Caused Jalapeno Leaves to Be Stripped from My Plant.

Q. I went away for three days and when I returned all the leaves were stripped from my jalapeño plants. Do you know what did this?

A. Leaves stripped from vegetable plants is usually because of their tomato hornworm. Tomato hornworms are large caterpillars with the spine sticking from their rump. They can come in a variety of colors but we usually see green ones.

            They are voracious eaters and can remove leaves from plants at an alarming rate. They also leave behind a lot of large feces that could be confused with mice.

            They select only tender tissue and may leave behind more woody stems because they are not as delectable. When plants are very young and tender, they will consume the entire plant.

            You do not see them during the day because they hide and come out to forage at dusk and during the nighttime. To find them, go out at dusk with a flashlight or in the early evening hours.

            Another interesting way to find them is using a black light, the same way to find bark scorpions. Hornworms shine with an eerie green iridescence under a black light.

            Your plant will recover but you don’t have much time left for pepper production. When leaves are removed this stimulates the plant to produce new leaves from existing buds in the crotch or axil of the leaf. The problem is now the plant will focus on producing new leaves first rather than flowers and fruit.

            Protecting your plants from these creatures is easy to do by going out at night and removing them by hand. Protect plants with sprays of Bt or Spinosad which are considered organic controls. Just about any vegetable insecticide will control them as well.

Pine Top Dieback Means Damage Near Top

Q. The top of my pine tree died.  Bottom branches look as healthy as ever, green, supple new growth on all of them.  It is about 20 years old.  Its watering has been successful for my 14 years in this house, infrequent and deep - it has options to gather additional water from adjacent areas (lawn and garden) if it wants. Why did it die?   Can I remove the dead top?  And what will happen? 

A. I looked at the picture and I tried to identify the tree. The needles are not very long so it did not look like one of our common pines such as Afghan or Mondel pines. It actually looked like a spruce from the branches and the needle length. The kind of tree is very important in determining what caused the problem.

            Whenever we have a portion of the tree die and the rest of the tree appearing healthy, it usually pinpoints the problem at the trunk or limbs where the green foliage is closest to the brown or dead foliage.

            If I were on site I would get a look at the trunk or limbs at the juncture between healthy and dead areas. I would look for mechanical damage in that area. I can’t tell you why there would be mechanical damage but that’s what I would look for. This is not something we would normally see with pine trees.

            If this is a spruce and not a pine then it might be heat stress. Spruce trees cannot tolerate our climate and soils very well and have difficulty lifting water from the roots to the upper limbs. If this is a tree that is not tolerant of our hot dry climate or desert soils than this could be drought at the top of this tree causing it to die back.

Control Root-Eating Grubs Organically and Conventionally

Q. I found grubs in the dirt with my plants. I put some Triazicide around the plants. Will this help?

A. Triazicide is a conventional insecticide, found at any nursery or garden center, which is very effective at killing grubs. The major advantage of conventional insecticides like this one is the residue or residual left behind after the application. For those preferring organic methods, this is also a major drawback.

            There are organic alternatives to grub control which are very effective. These include pyrethrum applied as a soil drench for an immediate kill, milky spore bacterium and beneficial nematodes. Milky spore bacterium and beneficial nematodes also give you long-term plant protection from grubs.

            In your case, you need something to kill the grubs. Once you kill the grubs, it may be no longer necessary for a product like Triazicide to hang around in the soil.

            A residual product like Triazicide becomes important when protecting valuable plants from an infestation which may be imminent. In cases such as these, mark the calendar when the insect threat might occur and apply this type of product two weeks to a month before this date.

            I would not use this product around food crops but lawns and ornamentals are more suitable. But always read and understand the methods of application stated on the label.

            Triazicide comes in several different formulations (liquid concentrate, granules, ready to use liquid, etc.) and each formulation is applied a little bit differently. Basically the poison is applied to the soil surface and water is used to wash this poison to where the grubs are actively feeding. Applying too much water can move the product beyond the area where it is needed.

            Manufacturers want you to be successful with their products so you will use them again and recommend them to others. They try to provide the best information possible so that you are successful.

            Be cautious around your outside pets like dogs and cats since any insecticide, organic or
conventional, moves easily from the soil surface, through the pads of their feet and into their body. I would not let them walk in the area until the surface where it was applied is totally dry.

When to Cover Winter Tender Plants in the Mojave Desert

Q. When should we cover Pygmy Palm, Bougainvillea and other plants that will freeze here in Henderson?  I have burlap to cover them.

Bougainvillea freeze damage

A. Both of these plants can tolerate temperatures to near freezing and they don't seem to have problems at temperatures below 45° F that causes chilling damage to some plants. Some tropical plants such as tomatoes may show chilling damage to fruit at temperatures below 45° F. This is why it is best to not refrigerate tomato fruits.

            It seldom freezes in the Las Vegas Valley before Thanksgiving. After Thanksgiving you might expect freezing temperatures at the higher elevations such as in Summerlin or in very low spots in the Valley where cold air collects. In Henderson, this might be in the old Pittman area or along the wash.

            Cold air, being heavier than warm air, settles into low geographic areas. Cold air tends not to settle on gently sloping land or hills.

            Freezing temperatures are more frequent where plants are exposed to wind. Plants growing along major streets tend to freeze more often than those in protected backyards. Major streets are urban canyons that channel cold wind in the winter. Backyards are more nestled away from these exposed urban canyons.

Sehgal palm cold damage

            Plants growing close to brick or cement walls that face West or South are less likely to freeze than plants growing further away unless wind is involved. Brick and cement walls exposed to the sun store heat during the day and radiate this heat at night keeping the plants a few degrees warmer. If wind is involved, it removes this radiant warmth making these plants more susceptible to freezing temperatures.

            Bottom line, when the weather forecast is for freezing temperatures, cover the plants with an old sheet, blanket, or in your case burlap, before nightfall. Drape this covering over the soil or any surface that can radiate heat at night. Remove this covering the next morning after temperatures are above freezing.

            In open areas, expect freezing temperatures after Thanksgiving and up to March 1. In protected areas, expect these temperatures anytime between mid-December and mid-February but watch your local weather forecast closely and adapt this recommendation accordingly.

Imidacloprid a Problem for Pollinating Insects?

Q. Do you recommend using imidacloprid in the grass to kill grubs? Does it harm pollinators? What would you advise?

A. That particular chemical is suspected of possibly damaging pollinators. Nothing has been conclusive about it but logic tells us that if we have a systemic insecticide that can persist in a plant for 12 months that it is possible this chemical may be in flowers, pollen or nectar. We just don't know.

For this reason I tell people if they are going to apply it to plants that bloom then apply it immediately after they have finished blooming. I also tell them that it is safest to use on plants which do not have flowers that attract bees. Lawn grasses do not attract bees so I don't consider that to be a problem for pollinators.

Even though it is labeled for fruit trees, I would not personally use it on fruit trees if I am planning to use the fruit. If I were to apply it to fruit trees or any ornamental tree that has flowers that attract pollinators, I would not apply it until after bloom until we have more conclusive evidence that it is not a problem with pollinators. That's what I am currently recommending regarding this product.

Moon Lagoon Eucalyptus Good Desert Landscape Plant

Replacement Plant for Photinia

Q. I have several Red Tip Photinia that I use as a screen from my neighbor. I would like to replace them with some a bush that would be about 3 to 31/2 feet tall and handle our soil an weather better. I want to spend a little time trimming them. Texas Rangers are good but need a lot of trimming. Any Suggestions?

A. Bob Morris forwarded me your message.   I am a Certified Horticulturist working in the Las Vegas area since 1992.

 I suggest you look at Dwarf Myrtle and Dwarf Youpon Holly. Both are tough evergreen shrubs growing to about 4 feet by 4 feet.

Hope this helps.
Andrea Meckley, CH
Imn2plants@aol.com

How to Move Established Plants in the Landscape

Q. A one-year-old tree was relocated from the front to the backyard. After one day, it appears obviously stressed. It lost all of its leaves. Our landscaper put on a combo mixture that included B12. They didn't prune it. I always thought you should prune about a foot off in order to stimulate the roots. What do you suggest?

A. Trees that have been in the ground for 1 to 3 years should move to new locations easily provided it is properly done at the right time of the year.

            Yes, I would normally prune back a tree or shrub after relocating at. This is a very important step in transplanting to reduce transplant shock. The reason is not to stimulate roots but to bring a better balance between the severed roots and the canopy.

            Transplant trees and shrubs when temperatures are cooler. I looked at the air temperatures reported when you sent me this email. They were still over 100° F. We are approaching the right time of year for transplanting but those temperatures are still too high.

            The tree lost its leaves because the severed roots could no longer supply enough water to the canopy. The tree responded to this “transplant shock” by dropping its leaves. This was its defense mechanism to preserve its life.

What is transplants shock?

            Transplant shock can come in many forms. The most severe shock results in plant death. Dropping its leaves was the trees defense mechanism that hopefully will save its life. By dropping leaves, there may be enough water the roots can supply to keep the leafless tree alive.

            Successful transplanting of trees and shrubs results in minor transplant shock. Minor transplant shock results in little to no dropping of leaves but a slowing of growth for the next one or two growing seasons.

            Plants established with drip irrigation can exhibit almost no transplant shock because the roots of the plants are concentrated close to the drip emitters. This makes moving them to a new location much easier.

Some Tips for Transplanting

            Here are some steps to follow when transplanting trees and shrubs that are one to three years old. First, wait for the cool temperatures of fall. In our area this would be mid-October to about mid-November. Move these plants soon after an irrigation.

            Make sure the new planting hole has been dug and the soil used for transplanting has been amended with compost and a starter fertilizer before moving the plant. When moving the transplanted tree or shrub to its new location, it should be placed in the hole immediately, planted and watered.

           
Second, with a sharp, round-nosed shovel, sever the roots deeply all around the plant a distance 12 to 18 inches from the trunk or trunks. Estimate the weight and size of the root ball you will be moving. Take as much soil with the roots as you physically can handle regardless of the size of the plant. Larger root ball size decreases transplant shock.

           
Minimize the time plant roots are out of the soil. Move the plant to the new planting hole will by lifting under it, carrying it by its root ball. An old piece of carpet, burlap or strong fabric works well.

            Gently lower the tree or shrub into the planting hole so that it will be planted at the same depth it was previously. Fill the hole with amended soil while at the same time filling the hole with water from a hose.

Stake the plant so the roots cannot move in a strong wind. Remove about one third of the canopy with the pruning shears to reduce transplant shock.

Cause of Ragged-Looking Japanese Privet Leaves

Q. I have in front of my house 5 big shrubs. Unfortunately I have no idea what they are called. They are getting water over our irrigation system.Today I took a closer look to my shrubs and found all 5 shrubs in really bad condition.
1. The leafs are full of white, at the edge brown dents, but only on the upper side.
2. I've noticed a lot of bees around and inside one of the shrubs.Perhaps cutter bees but I don't have  circled bites on my leafs
3. On one shrub I have a small white net, perhaps a spider net?

Here are my questions: Can you tell me the name of my shrubs and do you have any idea what my problem is?

A. The plant you asked me to identify in the pictures is called wax leaf or Japanese privet. It is not a desert adapted plant so it should be managed the same as other plants which are not desert adapted. It is native to Japan and Korea and so it prefers non-desert soils, medium light intensity, cooler temperatures and rainfall.

It is planted quite a bit in our desert and it always tends to look a little bad because it doesn't like it here much. It prefers climates that are not desert. This is a plant that should not be grown in rock surface mulch but in the wood chip surface mulch instead.

The usual reasons for this plant to decline in appearance is because the soil declines or becomes mineralized because of the loss of organics in the soil over time. The other reason it may tend to look badly is because of poor irrigation management.

If rock surface mulch is surrounding these plants please pull it away from them down to bare soil. I would put about half a cubic foot of compost at the base of each plant and lightly work it into the soil and irrigate thoroughly.

Next, I would check to make sure the irrigation is working correctly and there are enough drip emitters for each plant. Each plant should have at least two drip emitters located about 12 inches from the main trunk.

I would apply about 3 to 4 inches of wood chip mulch, not bark mulch, around all of the plants. Remove by pruning any parts of the plant that are ugly in appearance.

Fertilize the plants once a year in January with an all-purpose tree and shrub fertilizer. The easiest way to apply it is put a handful of fertilizer next to each drip emitter and water it into the soil. Irrigate these plants as you would any other trees and shrubs that are non-desert plants.

Follow-up Q. So, your opinion is that all the white dents (scars) on the leafs are a  fertilizing and irrigation problem? I have no fungus or bugs? And also the cutter bees inside the shrub are not connected to the visual problems ? Should I buy some insecticide?

Followup A. I know it seems improbable that irrigation could cause leaf damage like some of what you are seeing and I agree that is not the only problem. However, my experience with wax leaf privet is that they are out of their climate zone when grown in Las Vegas and growing them here puts a lot of stress on these plants.

The way to decrease the stress on these plants is to give them better growing conditions. This means soil improvement, planting them in the right light and heat exposure in a landscape, using organic surface mulches to continually improve the soil and maintain soil moisture and elimination of rock surface mulches that tend to mineralize the soil.

Once you begin to improve their health and decrease their stress most of the problems that you see will disappear. Then we can start looking for other things that are causing problems to these plants but the major problem you are seeing is due to their environment, either natural or manmade.

We do not have a lot of disease and insect problems on these plants. The diseases that we do have on these plants are from watering too often and poor drainage of water from around the roots. If these same plants were grown in central Japan where they are native you would not see the majority of these problems.

Las Vegas is not central Japan. Create an environment in your home landscape that is closer to the environment where they originate; soils have higher organic matter, light intensity is less, temperatures are cooler, humidity is higher. Try to re-create as much of this environment as you possibly can in Las Vegas; plant on the north and east sides of buildings where they receive shade from late afternoon sun, add organic material back to the soil, avoid rock surface mulches, etc.

When growing plants in the desert that don't belong here you must try to find locations that emulate where they came from as closely as possible. Apply management practices that emulate their original envrionment. Insects and diseases are not the majority of the problems with this plant.

By the way, the attraction of bees to this plant is typically an indicator that one of the sap sucking insects that secrete honeydew is present; aphids, whiteflies, mealybugs or scales. The bee problem could be cleaned up with sprays of soap and water on the undersides of leaves. After the plants are in better health then start working on the bee problem.

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Marble-Sized Mud Balls on Plant Leaves a Good Thing

Q. I sent you some pictures of a round object about the size of a large marble with an entry hole in it. I found it attached to the leaf of a cats claw leaf in my backyard of my Summerlin home.  I only have found one so I am not worried about lots of pests from this one vessel.

Potter wasp nest on cats claw vine leaf

A. I think this hard, mud-like ball with a hole in it, attached to a leaf, was left behind by a mason wasp. The mason wasp is also sometimes called a Potter wasp because of these round mud balls with a hole in it that resemble pottery. It has been theorized that Native Americans based some pottery designs from the mud balls left behind by Potter wasps.

            Wasps are generally divided into two categories; those that live with other wasps in a community which are called “social” wasps, and those wasp that live by themselves which are termed “solitary” wasps.

            Potter wasps are considered solitary; they live alone and build this mud nest for a single, solitary offspring. After building this pottery-like nest, the female finds a grub that will fit in it, paralyzes it by stinging and places it in the nest along with an egg. The developing youngster uses it for food.

            Potter wasps are not aggressive towards humans or other large animals unless they are provoked then they can sting multiple times without dying unlike a bee. They would be considered a beneficial insect in the garden area.

            Consider Potter wasp mud nests as one of the “good things” in gardens and landscapes. Just give the adult wasp its own space.

You can learn more about them here

https://polinizador.wordpress.com/2011/04/12/potter-wasps-and-mason-wasps/

https://en.wikipedia.org/wiki/Potter_wasp

Gardenia Needs Container and Extra Care in the Desert

Q. I love Veithcii Gardenia and I noticed that a local nursery has them for $10 for a 5 gallon plant. How do you keep the plant alive in the winter in Las Vegas and should it remain in a container and not in the ground? I have seen two of these plants in containers in Sun City Summerlin under a tree blooming profusely in the summer.

Gardenia In Las Vegas in filtered light

A. “Veithcii” is a popular selection or variety that has a longer bloom period than some others. Gardenias are grown by a number of home gardeners in our desert but you are right, they don't belong here so we have to put them in the right location and amend the heck out of that soil if we want them to do well.

            . It is best if they are grown in containers rather than growing them in garden soil. A good spot would be in filtered light which is what you would get growing them under some trees for protection from intense sunlight.

            Gardenias in general perform best in a bright northerly or easterly exposure. The soil should be 50% compost or at least high in organic matter. You can grow them in the ground but they will be more difficult to manage because the soil will slowly revert back to desert soil unless you continually add compost to the soil surface.

More about this Gardenia from Monrovia Wholesale Nursery

            It is also important to put a two or 3 inch layer of wood chips. I would use two drip emitters and never let the soil get overly dry. Fertilize 3 to 4 times a year and add a good iron chelate to the early spring application of fertilizer.

            The important things to remember is having a good soil, the proper exposure to light and irrigation frequency. The container should allow for drainage of water and you should see a small amount of water exit the container every time you irrigate. Good luck!

How to Rehabilitate Japanese Black Pine

Q. Are Black Pine, California Christmas Tree and Thumbergii all the same plant? I have 2 trees that are important in my landscape and have been doing well for several years. They were neglected recently so there is no place for deep watering and not fertilized in 2015. There is sap coming from the trunk. Should I try to rehabilitate them or replace them?

Japanese Black Pine

A. Japanese black pine is Pinus thunbergii so Thunbergii probably refers to Japanese black pine. I do not know if it is called California Christmas tree but I doubt it because Japanese black pine has a very unusual form making it a specimen plant in the landscape. It does not have the Christmas tree shape.

          Most of the textbooks say Japanese black pine tolerates alkaline soils but I have not really found them to be very tolerant of the hot desert and our soils. Many of them have been planted in Las Vegas but very few are still around which tells me many were removed.

          If you have Japanese black pine they are characteristically slow in growth and have a very distinguished form that adds character to a landscape. If you are looking for a Christmas tree pine this is not going to be it.

          They are slow-growing. If they have been neglected and do not look good they will rehabilitate very slowly. 

          Soil applied systemic insecticides that control borers would be a good if the trees actually have them. Pines can be “sappy” so make sure it is borers before you make the application. Wounding of the trunk and limbs can also cause them to bleed sap like borer damage.

          If you choose to rehabilitate them, put tree wells around the trunk about 2 feet in diameter to hold irrigation water. Give them a deep soaking with a hose once a month along with their normal irrigations.

          Fertilize them with 16–16–16 once a year in the early spring or apply it now if they haven't been fertilized this year. Punch some holes in the soil 2 to 4 feet from the trunk to a depth of eight or 10 inches. Put a handful of fertilizer in each of the holes and water them twice to activate the fertilizer and move it into the tree.

          Expect a very slow recovery if you choose to rehabilitate them. If they look bad now, I would suggest that you consider replacing them with something that you really like and can get instant gratification.

Air Pruning of Roots Another Form of Root Pruning

Q. I read about air pruning the roots of potted plants using either fabric pots or drilling holes in pots and lining with landscape fabric.  Supposedly, air pruning keeps the roots in "check" so that they do not outgrow the pot.  The idea sounds logical, but with our extreme heat and hot winds, could this work in Vegas?

A. Air pruning is allowing the roots of plants are exposed to the air and die. It is normally used in greenhouse production with potted plants. It can be used for plants growing in containers as well. It is popular where other types of root pruning may not be practical.

            If plants grown in containers are allowed to rest on soil or gravel, the roots of these plants can grow out of the holes on the bottom or sides of the container and into the wet soil beneath it. Once the roots leave the container and grow into the soil, the tops of these plants typically have big growth spurts.

            In the past, if these pots or containers were given a quarter turn twist, this would sever young roots and prevent them from getting anchored in the soil beneath them. This is an older method of root pruning.

            Another older form of root pruning was using chemicals such as copper sulfate applied to the surface of the soil or gravel just under the pots or containers. The concentration of copper would kill the roots of plants growing into it but would hurt the tops of the plant.

            Air pruning is another form of root pruning where the bottoms of containers are pots are suspended in open-air. Roots exposed to the open-air will die without moisture. As roots leave the container through drainage holes, the roots die and become “root pruned” by the air.

            This would work in our climate as well. However, in our hot desert climate I worry a bit about pots or containers left in full sunlight. The soils in these containers can heat up quickly and the roots “roasted” on the side of the container facing the sun.

            If pots or containers that you are using for root pruning are in full sun make sure they are white or shiny and reflect as much sun as possible. It would be best if they were shaded. Water the plants in the containers just before the heat of the day.