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Saturday, August 17, 2013

Wanted: Home Residential Landscape Sites in the Las Vegas Valley for a Research Study

I am looking for about 50 residential landscapes located in the Las Vegas Valley that would cooperate in a water use study.The study is being conducted by UNLV in cooperation with local water authorities. The study cannot offer much in return except that you might learn something about your landscape watering that you didnt know before.

This is what we are looking for:
  • It must be located in the Las Vegas valley.
  • Landscapes can be all desert, all turfgrass or a mixture of both.
  • Landscapes should already be on some sort of irrigation controller (clock).
  • The study will last about nine months.
  • There will be a small modification in how your irrigation system is run that is TOTALLY reversible after the study.
If this is something that you could partner in, please contact me at Extremehort@aol.com

Thanks for considering it!

Wednesday, August 14, 2013

Is My Photinia Over or Under Watered?

Q. I have no idea if I am over watering or under watering. My red tip photina plants are all brown and dropping leaves left and right. My sago is turning yellow. I have a drip system and it is set for twice a day ever other day for 10 minutes. Is that enough?

Photinia growing in rock mulch

A. Usually drip irrigation is measured in gallons per hour, not in the number of minutes it was operating. Each emitter operates in a specific number of gallons, or fraction of a gallon or liters, it will deliver in one hour. 

Problem photinia
Drip irrigation does not need to come on twice a day unless the drip emitters are those emitters I don’t like very much, the kind you can twist open and get some unknown volume of water. Under the right conditions those will put out so much water that it can run all over the place. Then you might need to have it come on several times just to keep the water in one spot.

With drip irrigation you should apply all of the water it requires in one application.  If your drip irrigation is operating at the same time as your lawn is being watered then this is a big no- no. This is frequently why drip is operating in that ten to fifteen minute range. Lawns should be irrigated separately from trees and shrubs. 

In your case, If your drip system is applying 2 gallons per hour through the emitters then the plant is getting 1/3 gallon each time you water which is 2/3 gallon total every other day.  The larger the plant, the more water should be applied to it.  For a one foot tall plant try and give it about 1 gallon of water each time you irrigate.  If your plant is 2 feet tall then try giving it to a gallons of water each time you irrigate.  If plants are 5 feet tall, give them about five gallons of water at each irrigation.  This is a very rough estimate.  My sense is that you may be under irrigating.

Photinia after corrective action was taken
Photinia have another big a problem if they are growing in rock mulch.  In rock mulch, they tend to yellow and begin to scorch around five years after they have been planted.  The soil under the rock mulch has become mineralized and they can not take up enough nutrients to satisfy their needs.  You can try to supplement these mineral requirements by adding a good fertilizer once or twice a year and an iron chelate to the soil in about late January or February.  Try using a good quality fertilizer for trees and shrubs like miracle grow and add an iron chelate to the soil such as iron EDDHA.  It is hard to find and expensive but usually Plant World Nursery on Charleston boulevard carries it.

If a Sago palm is planted in a very hot location with lots of reflected light it can begin to yellow.  It can also begin to yellow if we have a very low winter temperatures.  You will see yellowing due to very cold low temperatures very early in the spring or late winter.  If it is yellowing because of a lack of iron then the iron chelate mentioned above will correct it.  If the yellowing is because of watering too often then you may correct it by correcting your irrigation and not watering twice each day but watering only once on the irrigation day but applying more water.


How Do You Propagate Arizona Rosewood?

Q. How difficult would it be to propagate Arizona Rosewood? And how should I prune one to shape as a multi-trunk tree, with more foliage in the 6' to 12' height zone?

Arizona rosewood as a shrub
Arizona rosewood as a tree

A. It can be propagated from cuttings and seed. The easiest is from seed.

Cuttings of Arizona Rosewood should be taken in May and treated with a rooting hormone. Expect at best about 50% of the cuttings to root.

With seed, collect seed from seed pods when the pods are fully mature. Put into the freezer in a plastic bag for about 6 to 8 weeks and sow the seed in sterilized planting mix.

 Arizona Rosewood is a slow grower. With Arizona Rosewood you would want to select four or five main stems coming from the ground or very low on the trunk. These should be going in different directions to give the plant balance.

 Remove all new or existing small growth from these four to five stems and concentrate growth in the upper canopy. Thin the growth in the canopy  to major stems growing outward and remove growth going straight up or down, growing back toward the center of the small tree or shading other growth by growing too close together.

You will get faster growth if you have fewer stems. Growth will be reduced if you have LOTS of places where growth can occur. Always keep the canopy occupying at least half of the plants height.

 As the plant gets larger let the canopy occupy 2/3 of the height of the plant and keep the trunks free of new growth as soon as you see it. You can usually pull this new growth out and will not need a pruning shears if you get it when it is young.

Tricks to Container Gardening in the Desert

Q. I was wondering if there is a trick to container gardening? I have been using potting soil, along with plant food, and my plants keep wilting. What am I doing wrong?

A. I am not sure what is going on in your case but container gardening can give you some flexibility in growing things but it can also be a bit trickier because of the limited soil volume, how water moves through a container soil and finding or creating the right environment.

            Start with a container that is fairly large. Small soil volumes are difficult to keep moist during our desert heat. If the soil dries out, water will flow down the inside of the container wall and not wet the soil properly. If this is unmanageable, put a smaller container inside a large one to give it some shade.

Large containers have more soil volume which holds more water and help keep the soil cooler.

            When wetting soil in a very dry container, use a wetting agent with the applied water. A tablespoon of liquid detergent in a bucket of water will work. Add the detergent after the bucket is full of water and mix it.

            Always make sure the water can drain from the container directly out of the bottom to keep salts moving through the soil and out of the container. When watering, add about 20% extra water (1/5 of the volume applied) to keep salts moving through the soil or they will build and damage the plants.

            At every planting time, replenish 1/4 to 1/3 of the soil volume with new soil. Make sure the soil is good quality. There is plenty of junk being sold locally and in bags as well.

            Shade the container (not the plant) from direct sun during the day time. You can do this by double potting it.

Houseplant moisture meter
            Use an inexpensive soil moisture meter for houseplants to give you a rough idea if the soil is wet or dry. Otherwise lift or push the container. Containers get much lighter when it is time to water.

            Fertilize lightly once every one to two months during the growing season.

            If you have trees in containers, gently lift the tree from the container every three to four years, prune the roots, replace the soil, prune the tree to reduce its size and to bring it back to scale and replant it.

Pine Needles are a Benefit to Desert Soils

Q. We have nine pine trees and they are dropping lots of needles. We have a large berm under the trees and water inside the berm twice weekly. Should the needles be removed or left in inside the berm?

A. The needles are fine. If composted, they are said to be slightly acidic and will benefit our alkaline soils. If they are left alone in the basin, they will help mulch the soil, conserve water, reduce weed emergence and benefit the soil in general.

            A lot of needles blew out of the trees during the last storm event we had.  This is a normal occurrence and nothing to worry about.

Pine needles die for lots of reasons. Sometimes it is just old age. Some pines can keep needles on limbs for five years or more. Others only about three. They stay loosely attached or caught in the limbs even though they are dead. A big wind comes and blows them out of the canopy.

            If pine trees are getting plenty of water and fertilized once a year they will have a thick, lush canopy and grow about 12 to 18 inches a year. If water is not enough, they will not grow as much and not have a dense canopy. They will survive like that but just not be as thick and lush.

            Your berms should extend three to four feet from the trunk and deep and level enough to hold about three to four inches of water. Your watering frequency sounds right. Just make sure it gets enough water each time to move into the soil two to three feet or more. In sandy soils water needs to go deeper and more often.

Cutting Tomato Plants Back Now

Q. We actually took off the last tomato early this week.  Not fully ripe, but took it inside so no bugs or others would get to it. Somewhere I remember reading that you can cut them back to 12-16" and they will grow again. 

A. You can cut them back to some side shoots now but it will open the plants to sunburn if you are not careful and the plant may die. It is possible to cut them back now while it is still hot but make your cuts so that you reduce their height and still leave plenty of side shoots.

Sunburn on tomato on fruit and leaves.

            Another possibility is for next year. Try planting some from seed in early to mid-July. Put the seed between the plants and cover the soil and seed with straw to keep it moist and hand water daily. Make sure you mix compost into the soil in the spots where you planted the seed. Soak the seed in water four to six hours before you plant it. This will speed up germination. In about late mid to late August, cut or remove your old plants and let the young ones come in for production in September through November.

            Stake or trellis the plants and thin side shoots so you have better air circulation. Reduce any winds you have on the area with wind screens or windbreaks. Make sure you have at least 6 to 8 hours of full sun, fertilize lightly every 30 days AFTER you see flowering.

African Sumac Selection Present Problems to Homeowners

Q. I have read over and over that African Sumacs are fast growers. The African Sumacs here seem to be at a stand still! I have two in my backyard since April. They are alive but the canopy and trunk just seem the same, perhaps 10% growth. The trees are sold with tall, thin trunks - like 1/2 to 3/4 " diameter, with a canopy that branches out at 8 feet. There are no branches or leaves below that. The trees are staked high and the stems are all finger diameter. Will they take off eventually?

A. Trees with a long, skinny trunks with no side branches until 8 feet are a problem. This is done at the wholesale nursery to increase their height and make it easier to ship. It is to their advantage, not to yours.

            To have strong trunks, tree trunks to be tapered from top to bottom. In other words, to have good trunk strength the trunk needs to be bigger in diameter at the bottom and get narrower up the trunk. This helps to support the canopy. If they don’t, a good wind will come along and snap the trunks.  

Trees with no taper cannot support their own canopy. Leave any growth on the trunk that develops and stake as low on the trunk as you can to allow the trunk to move. Both of these things will help develop a tapered trunk.
            Trees develop tapered trunks from two major events in their lives; trunks swaying back and forth in the wind and the presence of branches with leaves all along the trunk. Both have a great deal to do with trunk taper and consequently its strength.

            When trees are staked, trunks should be immobilized no lower than it takes to hold the tree upright and still allow some trunk movement. The stakes should be removed as soon as possible after planting; usually no longer than one full season of growth.

            Next, never, never remove branches growing along the trunk if they are smaller than pencil diameter. Once these stems reach pencil diameter or thereabouts, cut them off flush with the trunk with a clean, sanitized bypass-type pruning shears.

            Never plant in a DRY hole. Make sure the soil in the hole is wet when tree roots come in contact with it. Planting in a dry hole can set a tree back, or any plant for that matter, due to root damage.

            Sometimes people say this is “transplant shock”. Well, yes, plants do have a setback, or shock, when removed from a container and placed in the ground. This can happen for many reasons but the DEGREE of setback can be under your control.  

            Why are they growing so slow? The amount of total growth on a plant (add up all new growth above and below ground) is divided by the number of places where growth can occur. Stems in full sunlight or without competition from other branches will usually be the strongest in growth but the total growth must be divided among every place that is growing. This includes the roots and any increase in the diameter of stems and trunks.

            If you want a plant to grow faster, reduce the number of places where growth occurs. Prune out unnecessary stems so that the growth is focused on those stems where you want growth to occur.

            You may see sprouts coming out of the trunk. Leave them. Do not prune them out until they are pencil-sized or larger but leave the small ones to help build caliper or taper.

Monday, August 12, 2013

Horticulture specialist Bob Morris says you can grow anything in the desert - Las Vegas Sun News

Horticulture specialist Bob Morris says you can grow anything in the desert - Las Vegas Sun News

Please Join Discussions About Desert Horticulture

I have been impressed with discussion groups. Members can add comments and their own experiences. There are lots of you out there who could contribute and lots of us will also learn in this exchange. If you have an interest in helping our desert dwellers, new and old, and learning in the process please join me in the Yahoo Discussion Group - Desert Horticulture.

aka Bob Morris
We had 85 people look so far, and only three people join.