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Monday, September 17, 2012

Fertilizer Formula for Keeping Crepe Myrtle Healthy in Desert Landscape

Q. We have a crape myrtle tree in our southwest back yard. It gets plenty of water and I fertilized it last month with some Miracle Grow flowering fertilizer. At the time there were some burned edges on some of the leaves and some yellowing. Now it is really burned on the edges of all of the leaves with yellowing. HELP!

Crape myrtle growing at Center for Urban
Horticulture for 20 Years on Formula
Mentioned Here
A. A couple of things on your crape myrtle. I have kept crape myrtle growing in raw desert soil in good shape for 20 years at the Center for Urban Horticulture and Water Conservation in North Las Vegas. I used a combination of a general purpose tree and shrub fertilizer (16-16-16) plus an iron application combined with foliar sprays of Miracle Gro.

            I don’t really endorse products but Miracle Gro is the one I used and have found to work just fine. You could just as easily use a different good quality foliar fertilizer for flowering woody plants. I apply the granular 16-16-16 in late January or early February using about 2 lbs. of fertilizer applied to the surface of the soil and watered into the roots without it washing against the trunk.

            You can make some shallow holes in multiple places under the canopy and water it in thoroughly. At the same time, I also apply an iron chelate, iron EDDHA at the rate of a tablespoon or two scattered in the same holes and watered in so that none of it remains on the soil surface. It is light sensitive.

            After about one month of new growth I then foliar fertilize the tree with a Miracle Gro spray or comparable product. I do both of these annually. You can do the same thing (except for the iron) by using a fairly large quantity of good quality compost annually. My guess is you either are missing the iron application, watering too often or not watering deeply when you do water.

Use Distilled Water or RO Water on House Plants

Q. I have a three house plants, a Christmas cactus, “Mother-in-Law’s Tongue” and an Orchid plant.  There is a white “fungus” looking on the top of their soil.  WHAT can I do to get rid of it?  Am I watering too much?  Indoors all the time.

A. It is difficult to diagnose without some pictures but this might be either a salt accumulation from using Las Vegas tap water coming from the Colorado Rivere or it could be fungus (mycelial growth) on the surface. Water taken from Lake Mead (Colorado River) at the Las Vegas location is carrying about six pounds of salt for every thousand gallons of water.

Our native desert soils also contain alot of salt. I assume your houseplants were potted with some commercial potting soil so the salt load is probably relatively smaller than our native desert soils. Over time this salt can accumulate in the soil (from the tap water and soil salt) and wick back to the surface of the soil as the water in the soil evaporates. This can leave a white crust on the surface.

Salt deposited on the soil surface from the Las Vegas
water coming from Lake Mead and soil salts left behind
when the water evaporates.
Remove the upper layer of the soil and repot the plant with fresh garden soil. Dilute your tap water with about 3/4 of the volume with distilled or RO water. I would not use pure distilled or RO water as this might cause some problems with your potting soils. Also when you water, make sure 1/5 of the water applied actually leaves the container out the bottom as drainage and discard. This helps to flush out the soil salts.

If this white thing is "fuzzy", this could be some fungal growth. Not all fungi are bad and some are decomposers and work to help break down organic materials that are already dead. Seldom do these fungi that feed on dead things attack healthy plants. Scrape off th surface, repot, keep air circulating around the plant and in sunlight when possible to help keep these fuzzies to a minimum.

How to Get Rid of Grubs in Your Compost Pile

Q. I started a Mulch bin about 10 yr. ago. It is about 4ft. by 6 ft. on the ground. Today when I went to get mulch for my vegetable garden and found a 1/2 dozen Grubs. How do I get rid of the grub and keep the worms?

A. First of I would like to refer you to a pretty extensive discussion I posted on my blog regarding composts and grubs in the compost.

Grubs from compost pile
 Secondly, we have to remember that these grubs, like earthworms, are decomposers... they are taking raw products from your compost and helping to convert them into a soil amendment of very high quality through their gut. But we also know that these are potentially problem bugs when they mature so as you already identified it might not be a good idea to cultivate them.

If it were me, the compost pile needs to be turned regularly to aerate it so it does not get anaerobic or it will get all sorts of problems. So if you are turning your compost pile then expose these grubs for the birds. Have you ever seen birds follow a tractor that is cultivating a field? the birds know that during cultivation all sorts of goodies are exposed and looking for a free lunch.

The other problem you may encounter (I am not sure because it is not clear) is that your compost pile might be in some location where the birds cannot get to it such as a barrel composter or the like. One advantage that worms have over grubs is their ability to move faster than grubs can. If the soil is starting to heat up, they will go deeper quite quickly while the grubs cannot. So another alternative is to cover the compost with clear plastic and heat the upper layers of the compost but allow it to be deep enough so the worms can escape. Keep it at 165F for at least 30 minutes and let the grubs cook and then let it cool down. The earthworms will again migrate back up to the upper surfaces or through the compost. A third way is to remove the worms. Heat up the compost with solar energy (clear plastic again) and re-introduce worms after it has cooled.

I hope this helps.

When Do You Pick Bartlett Pear?

Bartlett pear. The pear on the left is ready for picking.
Notice the skin color change from green (right) to
yellowish green. Notice also the seeds in the pear
on the left are brown. The one on the right is still white.
Q. Just this year planted a Bartlett pear, and a Comice for a pollinator. Both have pears on them now. But I thought Bartletts were supposed to ripen in August. I picked one of my four pears, chilled it in the refrigerator for a couple days, then let it sit for about three more days before slicing it. It remained hard as a golf ball and no tastier. When are they supposed to be ripe? 
A. Bartletts are picked when the color of the pear turns from green to a yellowish green but still hard. Then you must put it at room temperature to continue ripening and turn soft and buttery. If you let them soften on the tree, which you did not do, the flesh will be gritty with all those stone cells in the flesh.
Corky spot on Comice pear
If you pick just as the outside skin turns color to light or yellowish green, the flesh has more of a buttery texture. The pear on the left is the right color for picking. Also, the seeds should be brown inside when ready to pick. We are not picking Bartlett until mid September.

Just an aside, Bartlett usually does not need a pollinator in most of the Western United States. It does in other parts of the country. Also, be aware that Comice tends to get corky spot in our alkaline soils and may require foliar calcium sprays to correct that.

There is Lots of Salt in Las Vegas Water and It Can Affect Plants

Q. I saw that on August 12th you responded to a question regarding yellowing leaves on a Meyer lemon tree.  My tree has similar symptoms - though the yellowing is more spotty and on tips.  You advised to "give it a long deep watering about once every few weeks...to supplement the regular water to leach out the salts..." (emphasis added).
            I realize that soil make-up effects watering needs, but can you give me a ballpark as to how many gallons of  "regular water" per week is needed for these trees in Las Vegas in addition to the leaching you recommended?  My tree is approximately 7 feet tall. Should I spread these gallons out over a few days a week, or is giving it these gallons slowing on a single day once a week?

A. That’s actually a very interesting question and we have some research to back up the amount. There is about one ton of different kinds of salts (all of these together make up the "salt" content) in one acre foot of water that comes from the Colorado River (Lake Mead). 
Rose leaf with salt damage
            An acre foot of water is about 360,000 gallons. Unless you are on a well, this represents about 80% of the drinking and irrigation water provided by water purveyors (Las Vegas Valley Water District in the case of Las Vegas) in the Las Vegas Valley.
            This sounds like it could be quite dilute but actually when you water to a lawn from Lake Mead it will carry 4/5 ton of salt for every 360,000 gallons that are applied. This translates to an application of 800 pounds of salt for every 1000 square feet of lawn area each year.
Salt damage to pineapple guava from salt in the irrigation
            Bottom line, if this is municipal water it carries a considerable amount of salt. If you skimp on the amount of water that you apply and don’t overwater a little bit, this salt will accumulate around the roots of plants. This "little bit" of overwatering each time you water is only about 15%.
            So if you apply 100 gallons you really should apply 115 gallons to help move the salts out of the root zone of plants. If it is 50 gallons, then apply an extra 7.5 gallons. Ten gallons means you should apply 11.5 gallons.
            Few people are this precise when they water unless they are watering a golf course and paying $1M each year to irrigate an 18 hole golf course. So when you water you can apply a little bit extra each time you water (15%) or you can flush out the salts around the roots by adding an extra irrigation or two during the hot months to keep those salts moving out. I hope this helps.

Where to Get Pheremone Traps

Delta trap with pheremone inside
Q. Do you know where I can get pheromone traps for insects that cause damage in our area and also for thrips that damage nectarines?

A. Try Peaceful Valley at

            Pheremone traps can be used to identify what insect problems you have in your backyard orchard and when to spray. Commonly we use them for peaches, nectarines, apples and pears. You will want a trap for each insect and about three or four lures for each trap since they have to be replaced regularly. You will replace the lures about every 4 to 5 weeks until harvest then you can stop.

Wing trap with pheremone inside
            There are no traps for thrips. For thrips you will need Spinosad biological insecticide which you can get from local nurseries. The label may not say spinosad but may say something like borer, bagworm control. You may have to look at the ingredients to see the spinosad.

Must Cut the Roots of Italian Cypress to Put in a Block Wall

Q. We are thinking of taking out our wooden fence and replacing it with cinder-block wall.  The Italian cypress trees grow along 2 sections of the fence and are about 20 years old.  The new block fence will go on the other side of the wooden fence but there’s the footing to consider which will cut into the root system.  My question to you is, what are the chances of these trees surviving since we won’t know how much of the root will be cut into?  I can send pictures of the base of the tree with the irrigation and the existing fence post to give you a better picture of the area or I can send measurements of what I am planning.  Not sure if the pictures will give you enough detail to make an informed prediction. 

This is a picture of the soil around some oleanders after a
block wall had been removed and was being replaced. This
is not the readers but a friends. The oleanders were being
watered in a shrub bed with bubblers. Notice that there
is not alot of root development next to the wall.
As you know the trimming of these trees are time consuming and/or expensive to hire out.  We wonder if the block wall will bring more heat to the yard and could the heat from the wall burn the tree?   The reason we are considering this project is that with our dogs we are simply worried that if a plank snaps that our dogs will get out and possibly hurt.  We like to rustic look of the wooden fence but we wonder if the block wall might be a better choice for security.  Any thoughts on your part would be appreciated.

A. Let me talk about things I know something about, the damage to the trees if you decide to move ahead with a block wall, replacing a wooden fence.

    In the desert, plants grow where there is adequate water. If a good supply of water is on your side of the fence, the roots will tend to grow more in that direction. If there is lots of water on the other side of the fence, they may tend to grow in that direction.

Notice the difference between the shallow fleshy roots
of the palm tree (left) and the oleanders on the right. Palm
roots grow where there is more air, near the wall.
    So try to picture that your tree's roots will grow more in the presence of water. Would this be on your side of the wall or your neighbor's side? So if a cinder block wall is constucted, a trench will be dug and a footer laid to support this very heavy wall. You are right, this will definitely eliminate a portion of their root system.

   If these tree's roots are growing toward your neighbor mostly, then these trees will suffer significant damage. If your landscape is dry and the neighbor's is wet, this might cause severe damage to your trees.

    If their water is coming mostly from your yard and your neighbor's is dry, hen cutting the roots on the side toward your neighbor will probably have a more minimal effect.
This picture from Washington State University shows
how some plant roots will grow toward a good balance
of air and water such as close to the container wall.
    Likewise if their water is coming from a water source in small amounts from drip irrigation close to the trunk adn the resest of the yard is dry then the impact will probably  be minimal. In other words,if you are trenching in soil that stays dry for most of the year you will probably be okay.

    Another word of caution. The week before they put in the footer water the trees very well. Then let the soil dry out until they dig. Encourage them to dig, put the footer in and backfill the soil as soon as possible to minimize damage to the trees. As soon as possible, irrigate the trees again.

What Kind of Grass Do I Have?

If you see this on your sidewalk you have
common bermudagrass either
as a weed or as a lawn grass.
Q. We moved here last year and have not ever had the experience with the type of grass that is in our back yard. My husband says we need a four wheel drive lawn mower for mowing, extremely bumpy and patchy. What kind of grass seed should we be using here for this environment, and when to re-seed? Thank you and the Gazenias you advised me to plant and thick and healthy!!

A. It will be tough to tell but the two common grasses here are fescue (a bunching grass which might be giving you all the bumps) and bermudagrass. Bermudagrass runs along the ground and is flat. The bermudagrass, if that is one you have, will turn brown this late fall and early winter (November/December).

If you have a mixture of the two then you will see the parts of the lawn with bermuda turn brown this winter and the tall fescue will stay green in clumps. If you do have a mixture it is usually because of an inadequate irrigation system or not very good irrigation practices. The bermudagrass can survive with lots less water than the fescue. So when water is limited, the bermudagrass takes over those areas.
From left to right upper leaf surface of Kentucky bluegrass,
perennial ryegrass and tall fescue. Actually the tall fescue
leaf surface could also pass for annual ryegrass.

It is easy to spray and kill the fescue during the winter in the bermudagrass (beremudagrass is brown then and sleeping and will not get hurt) with Roundup but not the other way around. But most people do not like a bermudagrass lawn. Hope this helps.