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Tuesday, January 12, 2016

Many Ornamental Grasses Can Be Pruned Now

Q. When is the right time of year to trim grasses?
Some ornamental grasses are quite attractive during the winter and may be cut back just before new growth in the early spring
A. Most ornamental grasses are cut to within a couple of inches of the soil surface just before new growth in February. With some grasses this is done every year and other grasses it may be every 3 to 4 years.
Many ornamental grasses can be pruned close to the ground since new growth comes from culms at the base. Smaller grasses can be cut closer to the ground. Larger grasses should be cut higher from the ground. Dead growth in the center may indicate the plant needs to be divided.
            Remove any dead growth remaining with a rake. Fertilize the plant with a high nitrogen fertilizer, or a bag of compost, and a deep watering.
They should regrow from the pruned, remaining culms at the base.

Ornamental grasses need to be divided, or split apart, when the clump gets too large. It’s too large if the center begins to die out or flowering severely reduced. The plant is dug from the ground, the clump cut apart, cleaned up one of the smaller divisions replanted.

Containers for Fruit Trees Need to Be Appropriately Sized

Q. I have two dwarf trees, a nectarine and a peach. I would like to move them from in-ground into containers. What would you recommend the minimum size container to use?  The nectarine is about 4' tall and 5' wide. The peach is about 3' tall and 3' wide.
Fruit tree to be moved from the ground into a container

A. Use a container about the size of a half wine barrel for these trees. Do it any time until new growth starts, approximately the first week of February in our climate.
Use a sharp shovel. People don't normally sharpen shovels but it's a good practice to get into. You can sharpen it with a file or a bench grinder.
Cut through the roots in one push rather than whacking on them with a dull shovel. Cut entirely around the outside of the tree about 6 to 10 inches smaller than the inside diameter of the container.
After making the cuts in the soil all around the outside, use a pick or mattock to cut a narrow trench just to the outside of these cuts to a depth of about 12 to 15 inches. Use your shovel for leverage and gently lift the root ball from several different directions to loosen it.
24 inch nursery box used as a container for dwarf fruit tree. A box like this may last several years before it needs to be replaced and the tree repotted
Once the root ball begins to move, use your loppers to cut any roots that might be holding the plant in the soil. At this point, you should be able to lift the tree out of the hole with most of the soil remaining around the roots.
Fill the bottom of the container with soil amended 50/50 with compost so that the root ball rests 3 to 4 inches below the "lip" of the container. Place more amended soil around the root ball inside the container and water it in.
Prune the top of the plant by removing about 1/4 to 1/3 of the canopy to compensate for the loss of roots. The compost should give you enough fertilizer for the first growing season.

Oleander Does Not Need Iron Fertilizer after Pruning

Q. You mentioned pruning oleanders about a month ago. Should they be pruned in January or February? Do they need iron? My dwarf oleander does not bloom as good as my white oleander. What can I do to help them bloom better?

A. It is best to prune oleanders during the winter months because they produce flowers on new growth. Avoid pruning them in the spring after new growth has started or you will cut off all the potential flowers.
Oleander can be pruned close to the ground using a technique called rejuvenation pruning. This does not work well on all shrubs, just those that sucker easily from the base.
I’ve told people to cut oleanders to the ground, a method called rejuvenation pruning, and they will come back very nicely with some applied fertilizer and water. You can’t do this to all shrubs but oleanders respond nicely. Shrubs that tend to sucker from the base respond well to this type of pruning.
Dwarf red oleander doing well in rock mulch in Las Vegas
How late in the winter to prune, December, January or February, depends on how long you want to look at short stubs sticking out of the ground. If looking at stubs is objectionable, then delay this type of pruning as late as possible but before new growth begins. On oleander this is usually early February.
Oleander seldom needs iron so you should never have to apply iron fertilizer to this plant.
Some varieties of oleander don’t grow as well as others here. Some oleanders are more sensitive to freezing temperatures than others. Some oleanders don’t tolerate desert soils as well as others.

Soil improvement might be needed by this oleander. Prune the red oleander to the ground in early February. Then, apply two, 5 gallon buckets of compost around the base of the plant followed by a three or 4-inch layer of wood chips on top of the compost. Finally soak the soil around the plant with water. Do all of this in February.

A great website to visit to learn more about oleanders is the International Oleander Society

Ruellia A Good Choice for Desert Landscapes

Follow Your Dog with a Bucket of Water

Q. I have two large dogs that use my backyard as their bathroom. They cause yellow spots that turn completely bare and kill the grass. Are there any grasses resistant to animal urine?
Dog urine damage to a lawn is usually surrounded with grass which is darker green and taller because of the diluted urea fertilizer contained in urine

A. There are no lawn grasses totally resistant to dog urine. The high concentration of "salts" in the urine is causing the damage.
These salts are actually "fertilizer" salts, not bad salts such as table salt. There is just too much of it. The salts are so concentrated that the grass is burned or killed in a 6 to 8-inch spot.
If you look closely at "dog damage" to a lawn, it looks very different from brown spots caused by diseases or insects. Insect and disease damage does not cause the grass to become dark green or grow faster around the edge of the damage. Dog urine does!
Salts from the urine become diluted in the soil further from the “point of impact”. Once diluted enough, salts from the urine act as a fertilizer and turn the grass dark green and push new growth.
The key to decreasing urine damage is the same as too much applied fertilizer. Dilution. Drenching the spot with water and diluting the salts is the simplest way to decrease damage to the lawn.
I know this might be a hassle and look a little odd to your neighbors but if you follow the dog around with a bucket of water and dump it on the urine spot immediately after it is done, you have a good chance of reducing or preventing damage.

Now, if you could just train your dogs to do it evenly over the lawn and turn on the sprinklers.

Wormy Apples Pest Problems Vary with Regions

Q. I have a Fuji semi-dwarf apple tree that is about 23 yrs old in Kingman, AZ. The last few years I’ve had a terrible problem with worms in the apples. I clean up all the leaves after they fall and remove any apples that don’t fall. I  I spray dormant oil right before the flowers buds emerge or sooner and spray all around the area including on the grape vines nearby. I have wood chip mulch about an 8 foot diameter around the trunk. I’ve even sprayed Neem oil once when the apples are about the size of marbles but to no avail. Now I’m wondering whether I should remove the wood chip mulch as this seems to be the only thing left to try other than continual spraying or trying stronger chemical type sprays which I’d rather not do. What do you recommend?

A. Most likely this is codling moth and they attack the fruit several times during the year. Codling moth is an international pest of apples and pears. Their emergence coincides with rising temperatures and if you do not get control of the first flight they can multiply rapidly and each new generation can bet worse. 
Codling moth on immature pear fruit in Afghanistan
Codling moth damage on apple in North Las Vegas, NV
I am getting ready to begin writing up how to use pheromone traps for eliminating codling moth, rather than pesticides, in backyard and small scale operations if codling moth is not a huge problem in the area. I may also offer some classes on how to use them. I have been trapping insect pests like these with sticky cards and traps for years. They can be a very powerful tool for insect management.

If codling moth is a huge problem in your area, this might not work for you but it is worth a try. Stay posted and follow me on my blog for more information.

Tree Died. Planting in the Same Hole.

Q. I have a major borer problem with my nectarine tree. I will be removing it and replanting. Do I need to treat the soil before I plant another tree?

A. No. The borers that are problems in our climate (Pacific flatheaded borer or Flatheaded apple tree borer) do not enter the soil during any part of their life cycle. The borer you may be thinking of is the peach tree borer which we do not have in Southern Nevada but is common in more northern climates. 
Adult Pacific flat headed borer picture from Oregon State University

The peach tree borer does not actually enter the ground either but can be found low on the trunk near the soil level which makes you think it does. Both of these borers spend their entire life cycle either in the air as a beetle (our borers) or a moth (peach tree borer) in flight seeking a mate and looking for food to sustain itself until it can reproduce. The rest of the time is either as an egg laid on limbs or the trunk or larva tunneling and eating in sapwood where it can find carbohydrates for nourishment and growth. The final stage is pupal, also inside the tree, where it transforms from larva to adult beetle or moth.
One of the flat headed borers in a damaged branch of peach

Control by chemicals is not very effective for our borer since we don’t know when it flies or where it lands until we see damage. Having said that, there is one chemical that is very effective for controlling borers that are inside the tree and it is labeled for fruit trees. The chemical name is
One of the products recommended for borer control containing imidacloprid
imidacloprid. It comes as several different trade or label names. One of the common names for homeowners is a Bayer product found in many local stores and nurseries. It is a systemic insecticide that moves up inside the tree killing insects that are feeding on the interior. The claim is for 12 month protection using this product. Personally, I have a problem applying systemic insecticides that last 12 months on plants which produce fruit that I'm going to eat in less than 12 months. But it is labeled to do this.

Instead I recommend that we focus on prevention by protecting trees like peach and nectarine from sun damage to the limbs, We do this by keeping the canopy full enough to shade these limbs or painting limbs with whitewash to reduce sun damage by intense sunlight. Sun damage seems to attract the adults and their egg-laying. 

Midsummer die back of peach limbs due to progressive borer damage.
On older trees, damage from these insects might be over several years before visual signs of damage appear. At advanced stages of attack over several years, we see limbs dying in midsummer. Early signs of damage can be seen the day after a good rainfall when brown colored sap oozes from damaged areas.
Sap coming from peach limb due to borer activity

During early stages of damage we can remove the outer bark of damaged areas with a sharp knife exposing where they are living and feeding and revealing them to potential predators and exposing them to the elements. When this kind of practice is done on a regular basis we might see about 80% of the damaged trees recover until the next onslaught. Borers in peaches and nectarines are the usual reason these trees seldom survive past 20 years of age.

Tropical Themed Landscapes Possible in the Desert

Q. I have a pool that is being built and we're at the final stages of it being done. We are trying to create a tropical theme around the pool and most tropical plants don't do well in the desert. Do you have any suggestions? 

A. There is no reason you cannot have a tropical or Hawaiian theme around your pool using either desert plants or plants that thrive in our climate. There are dozens of of desert plants that resemble tropical plants and even some plants that grow easily in both climates.
Let me give you a list of some plant materials. There are so many to pick from that will fit into this theme. This just came off of the top of my head.
Some of the tropical look has to do with planting density. This area should be densely planted and use at least plants from three different size categories. Use more size categories if it's a larger area.
Be careful of focal points. Don't have too many of them but use plant color or dramatic changes in plant texture to pull the eye to a focal point. The focal point can be a waterfall, water feature, spa area, entry/exit of from the pool, etc. designing an area should make use of continuity and rhythm through plant repetition this is usually done through plant texture or color.

There are a few landscape architects and designers who read my blog. I am neither. Perhaps they will chime in with some pointers as well.Don't be shy and please let readers know who you are and how to get a hold of you.

Mesquite. Any of the Mesquite trees look tropical.
California pepper
Acacia, some of the smaller Acacia
Windmill Palm, Mediterranean fan palm

Larger Shrubs
desert bird of paradise
Rose of Sharon (hibiscus)

Small Shrubs
Nandina or heavenly bamboo
Mock Orange¶
ornamental grasses

Carolina Jessamine
Star Jasmine
Bougainvillea (freezes back each year)

Myoporum, sometimes called Australian Racer
Star Jasmine
Hearts and Flowers
Hen and chicks
Gopher plant

Red Hot Poker
Canna lilies

Vinca or periwinkle