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Wednesday, March 25, 2015

Microclimates Have Profound Effects on Gardens

Q. I live in North Las Vegas and am considering a vegetable garden in my backyard when I retire in January of ’16.  I have adequate space on east or west side of the house.  However, the west side has a high wall that blocks off the afternoon sun. Which side would be best for the garden?

Shade can have a dramatic effect on the temperature/humidity/light
microclimate of a yard.
A. I think of growing areas in the yard in terms of microclimates. It sounds like you may have two different microclimates going on; the warmer but shadier west side and the cooler east side.
I would consider having growing beds on both sides if they are significantly different in their environments. These two different microclimates can extend your production by a couple of weeks or more in the spring and fall; earlier spring and later fall production in the hotter microclimate and later spring and earlier fall production in the cooler one.

Reflected light also counts as light that the benefits plants as long as it is bright enough. I would not discount the west area simply because you have a wall on the west side. I would consider painting these walls to reflect more light or cover their surfaces for the same reason.

Think back when you have been in both of those areas and your impressions regarding their different microclimates. Was one microclimate quite a bit different in seasonal temperatures than the other? If these microclimates are so similar you do not get any advantage then I would put it on the east side. 

Barrel Cactus Problems Tied to Water

Q. Over the years I planted perhaps 10 different golden barrel cacti. Nearly all died the same way. I first notice a hole in the main body of the plant. It looks like a rodent gnawed the hole. I have never found anything inside the plant. The plant retains its color and appears healthy. After about a year the root system is gone and I remove the plant. Can you explain?

Golden barrel cactus with pups
A. When I lose a barrel cactus that way and the hole is at the bottom of the plant it is usually from poor soil drainage and watering too often. The roots rot as well as the interior. Reduce the frequency of your watering and make sure the soil drains extremely well.
            If you catch the problem early enough you can arrest the damage by shutting off the water until the plant recovers. After that, water less often.
If they are watered more than once every two weeks this might be the problem. They rely on storage water during times of water shortages. The size of the plant increases after a heavy rain and decreases when water is scarce because of the stored water.

The only creature that I would think might be interested in barrel cactus and might be able to damage them are ground squirrels. But they usually harvest fruits from them, not the fleshy interior.

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Argentine Cactus is Yellowing

Q. I have two quite large Argentine Giant cactus, each with many pups they've offset from their base. They are both located on a West facing patio, one is in a large pot and the other is planted in native soil. The one in the pot always turns yellow on its south side this time each year. The one in the ground does not. The potted one has been in that pot for about seven years, and I generally give it fertilizer a couple times a year.  I think I've even tried a bit of iron, though I don't really think that is the problem.

A. The usual reason for this cactus becoming a yellowish in color is sun damage, particularly if it only on the side facing the sun. Other possibilities could be the buildup of salts in the soil, lack of nutrients, root damage and cold damage. But the bottom line is stress.

Because the cactus has a restricted root system and has no ability to take water from deeper or surrounding soils, the plant may be more stressed in a container than the one planted in the ground. That's how I would view it.

The yellowing is resulting from stress. I think the plant in the container will stress more easily than the one in the ground. This cactus will turn yellow (side facing the sun) in a stressful microclimate when planted in the ground.

You should consider all of these as possibilities but I think it is most likely sun damage or bleaching of the plant tissue by intense sunlight. They will do a little bit better without so much intense sunlight, particularly the one in the container.
All that being said, make sure that the soil has adequate drainage and you are not watering too often so that you can eliminate root damage because of the soil kept too wet.

Choose a good fertilizer for it. I like Cactus Juice as a fertilizer for cacti and succulents. I've had a lot of good reports from people using this fertilizer on them.

When you water it next time make sure you add enough water so that a good 20% of the water applied comes out the bottom holes or moves past the roots to keep the salts flushed.

Cactus Baby Separation From Mother is Easy

Q. Is there any way to separate the babies from the mother cactus when they are joined along the stem or do you just let them grow?

A. Yes, you can separate the baby cacti, or the pups, from the mother cactus even if they are growing along its trunk. However, I would let them grow. They are quite interesting in a landscape when they are allowed to grow more naturally.

            The easiest cacti and succulents to separate are those which produce what we call “offsets” or sometimes we call them “pups”. Offsets are pups that are produced separately from the mother plant, usually on short rhizomes. The rhizome is cut which separates the pup from the mother cactus. The pup then is totally on its own and will send down its own roots and establish itself.

            Pups are any “baby cactus” or succulent whether it is an offset or attached directly at the stem. When pups are attached directly to the stem they can be separated from the mother plant with a sharp, sterilized knife.

The pup is allowed to “heal”for several days in a warm environment without any direct sunlight. This healing produces callus tissue which protects both plants from dehydration and diseases.

Once the healing has finished, the pup is placed on top of soil with extremely good drainage where it can root. The soil is moistened about every three weeks during this time. No rooting hormone is necessary.

This may not be the same cactus, but you can get an idea of what it might do.

it can add a very interesting element to your landscape if left alone.

Pecan Black Bitter Nut Damage Due to Leaf Footed Plant Bug?

Q. I have several pecan tree and some of the nuts I cracked this year have black spots on the nut and others have a soft brown film on part of the back of the nuts. What caused these problems and what can I do to prevent it.? The pecans have been producing for 30 years and  I have never had the problem until last year.

A. I am guessing that these black spots are on the meat or seed that you normally eat. I am also guessing that when you eat this pecan meat that it is bitter. If you are moving your head up and down in agreement then this is insect feeding damage by one of the stink bugs.

We do have stink bugs in Las Vegas but one particular type of stink bug or a close relative is the leaf footed plant bug which also damages pomegranates, pistachios and almonds.
Closeup of leaffooted plant bug. Photo contributed by Bill Stillman.

This feeding damage can cause the entire nut to drop off the tree or can cause these black spots to appear on the meat. To eliminate this kind of damage you would have to spray the entire tree with an appropriate insecticide.

You would have to start early because they will begin building their population on the tree as early as April. These insects also feed on tree leaves, vegetables and all of our major fruit trees. They overwinter on ornamental plants that remain evergreen in our landscapes.

The adults have wings so they can fly from neighbor to neighbor. Soap and water sprays will kill these insects if they are sprayed directly with this concoction. Soap and water sprays have no residual so no poison remains when it dries. This can be an advantage and disadvantage.

Other sprays are fruit and nut sprays that contain synthetic pyrethrins or pyrethroids. These will also work but the main problem you will have is getting the spray to cover the large tree from head to toe. These black spots can be broken off of the nuts and the nuts can be eaten with no problem.

Why Carolina Cherry Laurel Struggles in the Desert

Picture sent by reader of  the Carolina Cherry Laurel
Q. One of my Carolina cherry trees has some branches with brown leaves and the branches were easily broken off.  I have attached a picture of one of the branches.  There is an area of the main trunk, about halfway up the tree, which is very black.

A. I receive a number of questions regarding damage to Carolina cherry or that they don't look very good. The majority of the reasons why this plant struggles here is because it is native to the southeastern United States where the soils are rich and moist. They will struggle here if they do not receive TLC. The other problem may be where they are planted.

Closeup of the trunk. This is usually due to sunburn on the
trunk due to planting in very hot locations in the yard and
leaf loss that allows direct sunlight to damage the trunk.
Leaf drop of Carolina Cherry Laurel. In this case the cement
and bricks surrounding the plant could poise some problems.
            Your Carolina cherry laurel most likely has been damaged by the intense sunlight of our desert Southwest. When damaged by strong sunlight, we see limb and branch dieback accompanied by leaf drop.

Often times this damage is black with brittle limbs and bark that peels. Frequently the tops of these trees will die as well. They tend to look very
sparse in our climate and soils.

            Because this plant is not a southwestern US native, we have to be careful with it here. When planting it, the soil must be enriched with compost at the time of planting and the surface of the soil should be covered with wood mulch, not rock mulch.

            They struggle in very hot locations. This includes the south and west exposures of the landscape particularly close to the very hot walls. They perform better if clustered with other plants with similar soil and water requirements.

Same CCL as above but showing one is performing better than the other when
growing under similar circumstances. It is possible the one on the left will
do the same thing over time. It is also possible there could be some root disease
problems due to the cement and possible overwatering and/or collar rot disease.
            They may develop yellow leaves which would be corrected by applying an appropriate iron fertilizer. The one I always recommend is the iron chelate EDDHA. It is stable when applied to the soil regardless of the alkalinity. This is not true of other iron fertilizers.

Growing Tropical Hibiscus in the Desert is Not Easy

Tropical hibiscus growing in Las Vegas Nevada in the Mojave Desert.
Q. I'm forwarding pictures of my existing hibiscus that turned brown this past winter.  It actually looks like there's some growth on two of them but the others look pretty grim.  Should I give them a chance to grow or start again?  Also, if I do attempt to let these live should I trim them to the ground?

A. It looks like your hibiscus really got hammered this past winter. And this winter was not really that cold. These are most likely tropical hibiscus.

Hibiscus is a common name for a number of different plants with different attributes. These range from the tropical hibiscus to plants that we call hibiscus but are winter hardy in our climate.
Roselle hibiscus growing on MoCa Farm in the Philippines.

Your hibiscus was probably one of the tropical or subtropical types. Judging from your picture, the soil looks like it was hardly improved at all and rocks are strewn along the surface. These issues must be addressed if you expect these plants to do well at all in the future.

They need a lot of soil amendment added at the time of planting. Even though they can handle a lot of heat, they cannot handle the extreme heat and low humidity of unshaded south and western microclimates of the Mojave Desert.

They will look best protected from late afternoon sun and the soil covered with organic mulch. They will also do better if surrounded with plants that need moist, organic soils as well.

I would cut them to the ground in the spring, fertilize and water them and see if they will come back. Pull the rock away from them and put down a layer of compost about one inch thick followed by three inches of wood mulch on the surface. Keep the wood mulch away from the stems of the plants by about 12 inches.

In the future you will treat them like herbaceous perennials; let them grow during the warm and hot months and cut them to the ground after they freeze back. Pile mulch around their base that is three to four inches deep. This may be enough to minimize winter cold damage.

Here is an article we (MoCa Farm) wrote for Food Tank on the growing and culinary use of Roselle hibiscus in the Philippines. http://foodtank.com/news/2014/02/a-love-affair-with-roselle 

Tuesday, March 24, 2015

Vegetables and Herbs Presentation for Arizona Master Gardeners

This is the Presentation I made to the Arizona Master Gardeners in March, 2015, on vegetable and herb growing in the Mojave Desert. I intended it as a beginning primer for newcomers to gardening in the desert.

If there is a problem downloading this document, email me at Extremehort@aol.com and I will send it to you.