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Wednesday, March 25, 2015

Microclimates Have Production 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.

Monday, March 9, 2015

Viragrow Delivers! : March Coupons are Out!

Viragrow Delivers! : March Coupons are Out!: This months coupons are focused on renovating your lawn or starting a new one, fertilizing nonflowering trees and shrubs, roses, palms and ...

What Vegetables Can I Plant in March?

Here is a list of vegetables you can plant in March in the Las Vegas Valley. The Las Vegas Valley is around 2000 foot elevation (650 meters). Lower elevations can start earlier than this. Higher elevations can delay planting a bit.
Bush beans (s), broccoli (s,T), brussels sprouts (T), cabbage (T), carrots (s), sweet corn (s), eggplant late in the month (T), green beans (s), pole beans (s), kale (s), kohlrabi (s), lettuce (s), onion sets, onions (T), peppers late in the month (T), potatoes, radishes (s), spinach (s), Swiss chard (s), tomato late in the month (T), turnip (s)

T= tramsplants are best
s= cam be started by seed

You Can Still Prune after New Growth Starts

Q. Took your recommendation and planted a Dapple Dandy pluot and Santa Rosa plum in the same hole about 18 inches apart. New growth has already started to appear. What I’d like to do now is cut and lower the height of the Santa Rosa plum to the same height as the pluot. Is it too late to do that?
Pluot and plum planted in the same hole. Santa Rosa plum is one of the best pollinators for Pluots. The fruit trees are whitewashed to help prevent sunburn.
A. No, it is not too late to prune. People are mistaken when they think the only time to prune is during the winter months and when new growth appears, it is no longer permitted. This is a not correct.
            One of my professors used to say, “The best time to prune is when the pruners are sharp.” I still agree with him. However I would alter that by adding, “as long as it is a hand pruners.” If you are removing large diameter wood using a saw or loppers timing is more critical.

            In short, go ahead and lower the height of that pluot. Make sure you whitewash the upper surfaces of any exposed limbs to reduce sunburn unexposed branches. I will talk about summer pruning next month. I will post more about this topic on my blog.

Be Careful with Fertilizers for Tomatoes

High phosphorus fertilizers do not cause all vine and no fruit
A. Great advice from Linn! You want to give tomatoes a complete fertilizer at the time of planting. You can use organic sources or conventional fertilizers. It will not make much difference to the plant.
These can be applied to the soil or to the plant leaves if they are a liquid. After an initial
application of a fertilizer, phosphorus should be in abundance, not nitrogen, with further applications.
The problem with organic sources like compost added to the soil at the time of planting is that the fertilizers or nutrients they contain last so long. This is because the nitrogen in the compost is released slowly over a period of several months. This is not true of organic foliar sprays like seaweed extracts.
An overabundance of compost added to the soil will cause tomatoes to produce a lot of vine and delay flowering. This is not necessarily true of their close cousins, peppers and eggplant. If flowering is delayed in tomato and begins during the heat of the summer, it can result in little to no fruit production.
Example of a high phosphorus foliar fertilizer
to stimulate flowers and fruit
Inexpensive conventional fertilizers (farm fertilizers) release its nutrients quickly. One big shot is released during the first few irrigations and the amount of fertilizer available to the plant diminishes quickly after that.
These quick release or conventional fertilizers, at least the nitrogen component, lasts four to six weeks and 80% of it is gone. Quick release fertilizers, applied at planting time, are perfect for tomato growth and fruit production.

Foliar fertilizers, fertilizers applied as a liquid to the leaves and stems, act very similarly to quick release fertilizers applied to the soil. Liquid fertilizers applied to leaves last a very short time; 2 to 3 weeks.
Foliar fertilizers need to be applied more often than fertilizers applied to the soils. Foliar fertilizers should always contain a wetting agent to help that fertilizer gain entry inside the plant.
We want tomato plants to gain size quickly for about four weeks before they set fruit. If nitrogen is released in large amounts after that time, it will likely cause a delay in flowering and put on leaf and stem growth instead.
Example of a 1:1:1 fertilizer
If you are foliar feeding, you should have at least two different types of foliar fertilizers, maybe even three. The two which are most important are a high nitrogen content (highest first number) fertilizer and the second is a foliar fertilizer with high phosphorus content (highest second number).

If you get a third one then make it a fertilizer in a 1:1:1 ratio of nitrogen, phosphorus and potassium. Whenever possible make sure the third number, potassium, is also high in all three
fertilizers or make sure it is applied to the soil and available to plants.

Help Save My Photinia from Dying

Q. Our red tip photinia appears to be dying. It is 8 years old and receives full sun. The leaves are turning brown and dry.  Is there a disease causing this or is it the very hot weather we have experienced this summer?  We fertilize and  apply iron regularly.
Photinia with iron problems and soils with lack of organic matter

A. The usual problem with Photinia occurs when their planted in desert landscaping with rock mulch covering the surface of the soil. They are planted with some soil amendment in the planting hole which disappears in two or three years. Sometime during the fourth and fifth year Photinia begins to develop yellow leaves.
Photinia with the beginning of the decline

These yellow leaves become a brighter yellow and begin to scorch around the edges. If this problem is not fixed, Photinia gets worse and we see die back of the stems and the canopy of the plant opens up and looks very sparse. The problem is the rock mulch for this plant. They do not like it. They like organic soils, not soils covered in rock.

You have two options. Pull the rock mulch back and add compost to the soil around each of the Photinia about an inch deep and scratch it into the surface. Next cover the area with wood mulch, not rock mulch.

Add iron fertilizer and a regular fertilizer to the plants. Water them in thoroughly with a hose. Cut the Photinia back close to the ground and let it regrow. Hopefully this will get them off to a good start this spring. Continual additions of compost every two years will help this plant stay healthy.

The second option is to dig and remove these plants and start all over. Make sure the soil they are planted in as 50% compost mixed with it. Cover the soil with wood mulch and grow them out. Fertilize once a year in January with the commercial fertilizer for trees and shrubs and make sure you add an iron fertilizer at the same time.

Starting Texas Mountain Laurel from Seed

Q. I harvested some Texas Mountain Laura. Can I expect them to grow if I plant them in garden soil? Should I remove the outer shell first?
Texas mountain Laurel dried seed pods

A. Texas mountain Laurel can be started or propagated from seed but there is at least one major hurdle you must overcome. This hurdle is the very hard coat around the seed, not the pod.
The seed is best harvested from pods that have not fully matured. If possible harvest the seed from pods that have not yet turned brown but give you a clear indication that there is a seed which has fully formed.
Texas mountain Laurel
For seeds to germinate they must absorb water, be at the right stage of development, have warm temperatures and air. This very hard seed coat does not permit water to enter the seed and begin the germination process.

 To my knowledge, this seed does not have to be stored in cold temperatures prior to starting them from seed. Some seeds from temperate climates have to go through a simulated winter in the refrigerator before you plant them or they will not germinate. 
This seed does not seem to need this. However, to be on the safe side take half of your seed and give them an 8 week cold treatment in the fridge and take the other half with no cold treatment and see what happens. Give them a cold treatment before you damage the seed coat.
Damaging the seed coat without damaging the seed permits water to enter and start the germination process. If the damage to the seed coat is too deep, the seed may die.
           The easiest way to damage the seed coat safely is to use a file or sandpaper and scratch or nick the seed coat deep enough so this barrier is breached but not deep enough to damage the seed itself.
           There will be some variation in these plants because they are propagated sexually, that is by seed. When these seedlings first come out and reach about 1 foot in height you can begin to discard plants that don't have the size or shape that you desire. This is called "roguing" out the seedlings.

Here is a good website to look at.

This website seems to say it needs a cold treatment

Tuesday, March 3, 2015

When to Plant Tomatoes, Peppers and Eggplant?

Traditionally, by the middle of March at around the 2000 foot elevation in southern Nevada, we will have a 90% chance that there will be no more frost. This is normally the date we use for planting warm season vegetables.
Strong and vigorous tomato transplant

You can usually sneak them in a little earlier if you watch the weather forecasts or give them some protection. Tomatoes are warm season crops and they can suffer from chilling injury. This is damage to the plants if temperatures drop close to the same temperature in your refrigerator. Even a bit higher than this.

Hot microclimates in the yard can support please vegetables earlier than the middle of March. So if they are going in a spot that is West or South facing, you can put them in earlier.

Watch for temperatures below 50° F. If temperatures are going to drop this low, there is a potential for chilling injury.

You can use some hot caps and cover them at night when the sun goes down.

White woven crop cover rolled back showing the difference
in plant growth a crop cover can make in spring
You can use a crop cover and lay it over the top of them. These crop covers will give you an extra 5° F over the lowest temperature during the night.

You can throw a light blanket over them if you push in some short stakes to keep the blanket from crushing plants.

Or you can buy the plants and leave them in their containers. Put them outside during the day and move them indoors at night. This way you can delay planting them if you think there might be some low temperatures coming.

Strawberry Tree Needs Extra Care in the Desert

Q. I have a strawberry tree that is probably getting too much sun. The tips of the leaves are very discolored. Is there anything I can do to help it?

A. Strawberry tree is native to Western Europe and the Mediterranean region. 

Its leaves tend to yellow because of micronutrient fertilizer problems, cold temperatures and intense sunlight. Leaves also tend to scorch on the tips in very hot locations with intense sunlight. They do not perform well in rock mulch in south or western exposures.

Getting this plant closer to optimum health helps it tolerate stresses caused by extreme soil and environmental conditions. Soil improvement and wood surface mulch will help this plant a lot.

This plant should not be in rock mulch. Rock mulches radiate a lot of heat during the summer and add nothing back to the soil. If this plant is in rock mulch, I would pull the rock back a couple of feet and apply an inch or two of compost.

After lightly incorporating the compost into the upper soil surface, I would cover the exposed area with about 3 to 4 inches of wood chips. The combination of compost and decomposing wood chips will help to rebuild the soil around the roots. Rebuilding the soil around the roots improves the biological activity of the soil and overall plant health.

From your picture, the foliage otherwise looks healthy except for its scorched leaf tips. I would guess it is getting adequate amounts of fertilizer.

Applying fertilizers regularly to desert soils is frequently not enough to provide a plant with optimum health. Be sure to add an iron chelate such as EDDHA in a spring application of fertilizer once a year. The combination of the right kind of fertilizer, soil improvement and wood surface mulch will bring this plant closer to optimum health and better tolerance for hot locations.

When Should I Prune My Vitex Tree?

Q. When should Vitex tree be trimmed and how much should be cut?

Vitex in its winter form
A. Vitex blooms in early summer through late June or July. If this plant is pruned with a hedge shears you will likely affect how it blooms this summer.

Larger vitex in late June
Vitex with flowers in June
Any pruning done now should selectively remove entire branches back to a crotch. This is a pruning technique called “drop-crotching”. This technique reduces the size of a plant while still retaining its natural form. Drop-crotching avoids plant injuries due to “topping”.

Vitex in bloom in May
Limbs that add height or size are removed at the juncture with a branch of smaller size. This type of limb removal maintains terminal buds at a lower height, retains flowers and maintains the architecture of the plant.
The opposite of drop-crotching is topping, or shearing the plant at a desired height or size. We do not want to do that to most trees. After reducing the size of Vitex we would remove any crossed branches or broken branches and shape the tree to maintain its symmetry.

Sunday, March 1, 2015

Can I Save My Wind Damaged Tree?

A. yes, both branches can be saved or you can remove one of the larger branches but I know removing a large part of the canopy will make it look ugly.

Repairing this type of damage is best left for professional arborists. 

If you want to tackle this yourself or hire someone to do it under your supervision, then this would be the procedure you would follow. Pay particular attention in getting the right supplies for this type of job. 

Any permanent steel that enters and stays inside the tree should be stainless. Any steel outside of the tree that would be resistant to the environment would either be stainless or galvanized. But it is very important to use stainless on anything in contact with wet tissue inside the tree.

It is also important to make sure that the supplies you use are strong enough. Use American or Western manufactured steel products. Avoid Chinese made steel products. I have been very disappointed in the quality of some of these materials from outside the United States. I realize why they are available but these supplies have to be able to accommodate the bearing load of that tree in future years.

This type of repair to a very large tree is usually beyond the abilities of most homeowners. There is also the possibility of future liability if this work is not done correctly. Having said all that, these are the basic steps that should be taken.

Supplies you will need:

  • stainless steel eye screws with a length long enough to penetrate 1/3 the diameter of the limbs
  • galvanized, stranded wire cable with a working load limit capable of supporting the canopy (for large canopies cabling may need to be done in multiple locations)
  • stainless steel partially threaded rod, washers and nuts

Equipment you will need:

  • chainsaw or arborists handsaw large enough for drop-crotching limbs
  • power drill or manually operated brace
  • wood bit long enough to drill a continuous hole through the split to accommodate the partially threaded rod

1. Reduce the load (weight) on both sides of the split by removing some of the top growth. Use a technique called drop-crotchng to remove top growth. Drop-crotching is selective removal of branches. The removal of these branches is at the “V” where the tallest branches come together with a side branch. Removal of these limbs should be just outside the “collar” of the limb to promote faster healing. Sanitize and disinfect all blades or bits used for entering the tree prior to its use.

2. Drill pilot holes for the eye screws into major limbs for securing the stranded cable. Secure eye screws into the major limbs a distance into the tree of one third the diameter of those limbs. Eye screws should be stainless steel, not galvanized or zinc plated. Large canopies may need two or more locations where eye screws are inserted and cabling is secured.

3. Secure stranded galvanized cable through eye screws and use a block and tackle, come-a-long or winch to pull these major limbs together enough so that the split visually disappears. Treat the top of the split with grafting wax to keep water from penetrating to the inside of the tree. The grafting wax is not permanent but helps keep water out of the crack until compartmentalization of the damaged area can occur. You can also use water-based asphalt sealer.

4. Drill a continuous hole through the trunk at the split. The hole should be continuous to accommodate a steel rod large enough in diameter to assist in bearing the load of the canopy.

5. Insert the stainless steel rod and secure both ends with stainless steel washers and nuts. Tighten the nuts to assist in bearing the load of the canopy.

The tree will eventually engulf the steel rod, washers and nuts. You should remember to notify anyone who might remove the tree that there is a steel rod in the interior at the split.

You can read more information on this and see some pictures of how this is done at:

Black Spot and Rust Not Common in Vegas Roses

Q. Here's the pic of what's going on with my roses.  What do you think?  Black spot or rust?

A.This was sent to me in July, 2014.
I really didn't see any black spot or rust in the picture. Black spot of roses have the typical "black spots" on the leaves and rust are pustules on the leaves that can be rubbed off with your fingers.
Both are more common during the spring, periods of high humidity and too much shade. Usually full sunlight, drip irrigation (no overhead irrigations), watering during early morning hours, fertilizing regularly and our dry conditions seldom lend itself to either disease here.
If you need to put on a preventive treatment on roses in the spring or fall, apply one of these treatments to the leaves: sulfur dust, Neem oil or compost tea.
The damage looks more like spider mites, drought or lack of fertilizer. Make sure roses have an organic surface mulch applied to the top of the soil that decomposes (wood chips), use drip irrigation, water early in the morning and are fertilize during the spring and fall months. 

Sunday, February 22, 2015

How to Correct a Bad Haircut on Rosemary

Q. I have a rosemary bush in the front yard that's very healthy but has grown quite big in the seven years since it was planted. Is there a technique to trimming? I tried once before and it looked like a really bad haircut.

A. Rosemary can be quite dense in its interior if it is watered and fertilized normally. It becomes denser if it is pruned with a hedge shears. If rosemary is very dense, very little light penetrates inside the canopy. This lack of interior light causes leaf drop resulting in an interior that is only wood.

Pruning with a hedge shears results in a surface layer of green foliage only an inch or two deep. This surface layer of green foliage is new growth which has been sheared. If left draped over a wall, the new growth may be several inches long.

Dramatic pruning of an older plant can result in that “bad haircut” you mention that reveals its woody interior. The only portion that can be removed safely without causing a “bad haircut” is a small portion of the green surface layer.

Rosemary will regrow once it has a bad haircut but it takes time and you and others are forced to look at the bad haircut until it grows back during warm weather. Any extensive pruning of rosemary that can result in a bad haircut should be delayed until warm weather.

You have two options. The first is to go ahead and give it a bad haircut beginning in about April knowing full well will take time to recover. The second is to remove older plants and replace them with younger plants that you can begin to shape at an early age.

Once pruning has been initiated with a hedge shears, the shape of the plant is difficult to correct. If you wanted to be an ornamental rosemary is one of the easiest plants to prune. It adheres to any shape you want to give it.

At Christmas time rosemary is available in nurseries in many stores shaped into 3 to 4 foot tall Christmas trees. I've seen it planted around trees and the shrub is carved out around the trunk. I've seen it planted in a raised planter and cut off along the wall like bangs of the haircut.

I prefer a more normal look which used to reach deep inside the plant and remove older wood. Every time you make a cut, it is hidden by the growth that's remaining. If you prune like this, it will never look like you even touched it except it smaller.

Look for the growth that is longest, follow the stem back inside the canopy of the plant to a place where there is side growth or side branch. Cut just above this side branch so the side branch can continue to grow but you are removing the longer stem.

Usually you would do this in three or four locations. Depending on how restrained you want the rosemary to be, you might do it annually or every 2 to 3 years.

Prostrate rosemary in natural form in rock landscape

Companion Planting Successes Can Be Variable

Q. I am looking for a spring companion list for Las Vegas. I have an easy to read chart for fall in order to know where to put different plants and which ones don't like to be next to each other but can’t find the same resource for spring.

A. The topic of companion planting is very large and has a lot of good information but unfortunately it also has a lot of folklore that is either regional in nature or lacks validation.

Companion planting can focus on the inter-planting of crops, the use of understory crops, the planting of trap crops, suppression of pests by other plants, planting to increase the levels of predators, and more.

For the general public, the term has evolved into the planting of crops for mutual benefit. These companion plants are sometimes referred to as “friends” to other crops without getting into much detail.

There is good evidence for the planting of trap crops for aphids, whiteflies, nematodes and a few other pests. I have heard anecdotal evidence for the use of plants like garlic for repelling certain types of insects or even rabbits. Some people will swear by it and other people who have tried it may say it doesn't work.

This opens another set of problems because in some cases it may work and in other cases it may not which causes confusion. I have tried to maintain neutrality on these issues and recommend situations where I am comfortable there is solid scientific research to support it or not support it. People are free to post their suggestions on my blog and I will publish them provided they are commercial neutral.

Where I am comfortable recommending companion plants are in the areas of trap cropping, inter-cropping and the planting of understory plants. There are some very good evidence that interplanting of crops can have some big benefits including a reduction of pest problems compared to large-scale monoculture where only one crop is grown.

Without getting into detail, there are areas I am very uncomfortable making recommendations because there is contradictory information or the research flatly does not support it.

For people like yourself who want to experiment in these areas, I strongly support it and test it for yourself. No one can dispute it if it works for you. There are publications that do support this kind of gardening activity such as

Other sources you may be familiar with include MotherEarth News, Old Farmer's Almanac, and many others.They are fun to read!

A balanced assessment of companion planting was done by Cornell and can be found at http://www.gardening.cornell.edu/factsheets/ecogardening/complant.html 

How to Prune Arizona Rosewood Against a Wall

Q. I planted a 5 gallon Arizona Rosewood a year ago against a wall for visual screening. How and when should I prune it?
Arizona Rosewood one year after planting
A. This plant can be grown as a shrub or small tree. As a shrub, led it continue to grow as it is except for any weak stems. Any weak, floppy stems should be cut back about 1/3 to half their length to encourage them to become stronger.
As a tree, it can be grown with a single trunk or multiple trunks. This initial pruning to establish its architecture or form should be done during the winter or early spring. It is not too late now.
If your plan is to use this as a small tree, then I would select 3 or 5 larger diameter stems (an odd number is more pleasing to the eye) coming from the ground and eliminate all other growth coming from the base. As new growth appears from the base, eliminate it at any time of the year you see it.
Next, stake these stems individually in an arrangement you would like them to grow. Staking young stems for one year will encourage them to continue growing in those directions. Finally, cut any long, floppy stems back to encourage strength. Make these cuts ¼ inch above a side branch in any direction away from the wall. Remove any strong growth growing towards the wall.
Here is some excellent information with more background on Arizona Rosewood by an extension agent in Arizona.

Why Are My Leaves Yellowing on Loquat?

Q. The leaves closest to the trunk of my two-year-old loquat have started turning yellow and falling off. New leaves have started to grow and they look fine. It was a 5 gal tree when I planted it. Last year the tree grew very well and produced a few loquats.This year the amount of fruit appears to have doubled but it has developed this leaf problem. 
I did some research on loquat leaves turning yellow. They suggested overwatering might be the problem.  I give it about 24 gals of water once a week. I checked the soil with a moisture meter and it does not show being wet.

A. I cannot give you any definite answers why your loquat has initiated leaf drop and yellowing of the leaves. I can tell you this; many leaves will yellow just before they drop from the tree so this type of yellowing just means that the leaves have died and will drop soon. The leaf color of loquat without chlorophyll is yellow.
When the tree has initiated the dropping of its leaves, the leaves will lose their chlorophyll and hence their green color. The remaining color after the chlorophyll has disappeared will be yellow due to the presence of carotenoid pigments which are masked by the presence of green chlorophyll.
Most likely this tree went through some sort of shock. This shock initiated leaf drop. The shock can be related to water, salts including salts from fertilizers, a light freeze, toxic chemicals or salts such as a high concentration of fertilizer applied to the leaves, etc.
The water-related problem can be from too much or not enough. For instance, if it went through a very dry spell it will drop its leaves. If the soil is too wet for an extended period, it will drop its leaves. If fertilizer was applied to close to the trunk or the rate was too high for the plant, it will drop its leaves.
There are two types of overwatering; one is related to the volume of water the plant is given while the other one relates to how frequently the water is applied. The overwatering I am talking about is applying water too often, not overwatering due to applying too much water in a single application. Once a week is not too often in my opinion unless you have a drainage problem.
If you do not think the soil has been too wet or you have not fertilized the tree by either applying fertilizer to the soil or spraying leaves, then I would just wait and see what happens.

If you applied fertilizer to the soil and you suspect the application was too strong, then flood the area with water and push the salts through the soils and away from the trunk and past the roots. That's probably the best I can do without more information.

Wednesday, February 18, 2015

Should We Keep Politics Out Of Gardening?

I'm not so much asking a question as telling one of my solutions. My garden is along an East facing concrete block wall and though shaded in the afternoon there is still considerable heat coming off it during the summer.  

Add caption
Two years ago I stopped someone picking up election signs and asked if I could have some.  They said yes and I got enough to do most of my garden.  Through procrastination and adult life I didn't manage to get them onto the wall until late June.  My tomatoes were growing OK but they were leaning away from the wall and you could really feel the heat when close to the wall.  I mounted the signs on the wall to kinda insulate it from the sun in the hopes of reducing that reflected heat. 

It worked really well as within two weeks the difference was noticeable.  The plants had started growing more upright and appeared to take on a new life.  This year I got some more and expanded the coverage to the entire garden.  Took less than two hours and I'm hoping it helps to grow a bumper crop of tomatoes.

Pictures attached hopefully.  You can use all of this if desired but please, no name or e-mail address.  Thanks.

Now if I could just figure out what's wrong with my peach tree I'd be set.

Seed Exchange and Music in 29 Palms March 1

I hope all of you in the 29 Palms area will help support this event! It sounds like lots of fun and a great way to get some local seeds that have a proven history of success.

Sunday, February 15, 2015

Prune Grapes to Improve Production

Our climate in the Mojave desert can damage grapes during the cold winter months. This winter was warmer than usual and the two times it dropped into freezing weather this winter was when plants were deeply in their winter slumber.

That's good. Freezing weather occurring early in the fall or late spring is typically more damaging than the same freezing weather in midwinter.

For small-scale producers and backyard gardeners I like to tell them to prune their grapes last. Wait until the most brutal part of the winter is over and then prune. The reason for this is simple. When we prune grapes we typically remove everything on the plant that is not necessary. When we are finished pruning we leave behind very short Spurs or longer canes depending on the variety of grape.

Regardless, for good production we need everything that we have left after pruning to be alive. Temperatures in the Mojave desert can drop to temperatures that can damage grapes. If we prune grapes too early and this is followed by very cold temperatures, we can lose some and possibly most of our production because of the death of these spurs or canes due to cold.

Here are some tips on pruning table and wine grapes:

1. When you prune grapes and the temperatures are warm, grapes will bleed. That is, you will see water coming from the cuts. This is normal. This is water being pumped up the vine by its roots in preparation for spring growth. They may continue to weep like this until growth starts and the leaves suck this water away from the cuts and the cuts have a chance to heal.

2. Identify all of the growth that occurred last year. This will be a different color than the older growth or it just will not look as old. Once you have identified last year's growth, you can cut all of them back so that the new growth is about 18 to 24 inches long. These long canes are where your grapes are going to be produced.

3. Space these long canes which will produce grapes about 12 inches apart. You want to do this for table grapes because this will encourage the berries to become larger. You want to do this two wine grapes because you want to concentrate the flavors developed by the plant into fewer berries. Choose healthy and vigorous canes to be your producing canes. Identify any canes that are between your producing canes. You can either remove these or them back and remove all of last year's growth. If you remove a cane, you will remove the fruit.

Grape pruning progression for spur pruned grapes. Cane pruned grapes are just
longer spurs.
4. The remaining canes will be cut back to about an inch long (spur pruned) or about 12 inches long (cane pruned). If you want to get technical, identify the buds on the canes. When spur pruning, leave only one to two buds remaining. When cane pruning there should be 10 to 12 buds remaining.

5. If you have Thompson seedless grapes, or Black Monnuka do not spur prune them. These should be cane pruned. Make sure you have 8 to 10 buds present on the cane when you're finished cutting.Most other table grapes are spur pruned. Most wine grapes for our climate are also spur pruned.

Here are some previous posts on my blog concerning pruning grapes.

How to Control Whiteflies on Tomato This Summer

Whiteflies on the bottom of pomegranate leaf
Q. I am new to gardening in the desert and am surprised at my success thus far!  That is, until the white flies came.  They showed up on the grapes and zucchini first, maybe in May or June.  Unfortunately, I didn't think they would become a problem. By August they had attacked everything! I pulled broccoli plants and found I needed a mask to keep from inhaling them! What can I do this season?

A. Whiteflies are a very tough to control once they get established in the numbers you are talking about. They are much easier to control if you’re diligent about controlling them when you first see them.

Females lay a couple hundred eggs at a time and these become adults that can lay more eggs in about six weeks. This means you can have exponential growth in their numbers if they are left undisturbed in six weeks.

Whiteflies, like so many garden pests, do not show themselves but remain hidden. Unless you stoop over and turn over leaves and look at their undersides, you will not know they are there until you see their telltale signs of plant damage. Signs of damage are yellowing and scorching of older leaves, sticky residue on upper leaf surfaces of lower leaves and ants.
Bottom leaves of sunflower yellowing and scorching due to past problems on the bottom side of the leaves.
Photo courtesy Viragrow.

Ants love the sticky residue that whiteflies and aphids produce. Ants climbing on plants in the garden or on fruit trees is a very good sign you have a developing pest problem.

Backpack sprayer suitable for vegetable and Orchard spraying
If you buy transplants to put the garden, spray the undersides of the leaves and the stems with insecticidal soap, neem horticultural oil. Once the transplants have been placed in the garden and they have grown a little bit, remove the bottom leaves of transplants that are within a couple inches of the soil.

These bottom leaves are perfect hiding and living quarters for many of the problem insects. They are so close to the soil surface they can’t be sprayed effectively.

Stay away from conventional garden insecticides unless this past really gets out of control. Whiteflies are resistant to many conventional pesticides and these traditional pesticides can knock out whitefly predators that help keep them under control.

Get yourself a decent compressed air garden sprayer such as Solo or Chapin and use soap and oil sprays in rotation with each other. Early in the season when it is still cool, check the undersides of the leaves and look for critters.

Weekly applications are probably enough during cool weather. When it starts to get warm, inspect the bottom sides of the leaves and spray twice a week. Make sure you spray the undersides of the leaves. That’s where these critters are!

Control ants that are getting into the garden. They are buddy buddy with aphids and whiteflies. Ants come from a nest in the ground. Follow their entourage back to the hole in the ground and treat around the hole with a bait that they can carry back to the nest. These are the most effective for ant control.

If you see bottom leaves that are starting to get yellow, pinch or clip them off. If they started to turn yellow they are contributing to the plant anymore. Look at the underside. There are probably critters feeding away. Removing these leaves, removes pest problems.