How Do You Sterilize Pruning Equipment?

Q. You often discuss the need to "sterilize" your garden tools to prevent transfer of disease. How do you "sterilize" these items?

A. A. What I mean by “sterilize” is exactly what is meant to a medical doctor and for some of the same reasons. Not sterilizing pruning equipment before its use is a terrible oversight. People overlook cleaning and sanitizing equipment because people don't understand why it is needed.

99% of the time unsterilized equipment is not a problem. It’s that 1% of the time when it becomes a problem. These are the times I receive questions about the dieback in olive, mulberry, silk tree and perhaps even ash trees.

Diseases are transmitted. Several important diseases are transmitted on pruning equipment. These include sooty canker (fungal disease of mostly ornamental plants), fire blight (bacterial disease of

Mimosa or silk tree die back due to Verticillium wilt.

many ornamental plants and fruit trees), crown gall (bacterial disease of many woody plants), slime flux (bacterial disease of many plants), Exocortis (viroid disease of citrus and tomatoes), bacterial spot (Xanthamonas, a bacterial disease), sudden oak death (fungal disease), figure mosaic virus, rose mosaic virus, tobacco mosaic virus, Fusicoccum viticolum on grape (fungal disease), Pierce's disease of grapes (5% transmission rate, bacterial disease) and others. I did not include tropical plant diseases like papaya ring spot virus and banana wilt.

Sooty canker on ash.

Cut flower growers and florists also realize the importance of sanitizing knives and pruners to prevent infections from entering the cut flower and promoting its longevity.

Whenever we enter fresh plant tissue with a pruning shears or saw the equipment needs to be sharpened, cleaned and sanitized. Adjusted and sharpened pruning equipment provides a narrow point of entry which minimizes plant damage around the cut. The concept that gardening tools should be kept clean, adjusted and sharpened is less controversial since this makes sense to people.

Equipment should be adjusted, sharpened and sterilized at the beginning of a pruning day. Equipment used for pruning should be sterilized for the same reasons we sterilize hypodermic needles and scalpels. Several important diseases are transmitted on pruning equipment. You can read more extensively about this topic this week on my blog.

Sanitize and sterilize pruning equipment. Here I am using an alcohol wipe after cleaning, sharpening and adjusting the blades.

Unlike a medical procedure which usually enters the body in one location, pruning involves entering the plant multiple times at different locations. So when pruning we must be concerned about transmitting a disease from plant to plant and the possibility of spreading a disease on the same plant to multiple locations.

If trees are healthy, then there is no reason to sterilize or sanitize pruning equipment between cuts or between trees. If the disease is present or you suspect a disease, sanitize between every cut to prevent the disease from spreading within the tree.

What to use for sterilizing equipment? First of all, wash the cutting surface of all pruning equipment with soap and water. Removing dirt and debris from the cutting surface improves the efficacy of sanitizing materials. It also prolongs the life of sanitizing solutions.

Sterilizing methods have been researched and there is some disagreement about what works best. Sterilizing solutions recommended include household bleach, Pine-Sol, rubbing alcohol, trisodium phosphate (TSP), and household disinfectants. 

Household bleach (ex: Clorox): 25% solution (1 part bleach + 3 parts water)

Pine oil cleaner (ex. Pine-Sol): 25% solution (1 part cleaner + 3 parts water)

Rubbing alcohol (70% isopropyl): 50% solution (1 part alcohol + 1 part water)

Denatured ethanol (95%): 50% solution (1 part alcohol + 1 part water)

Trisodium phosphate (Na3PO4): 10% solution (1 part Na3PO4 + 9 parts water)

Quaternary ammonium salts: use as directed on product label

Household Disinfectants (Lysol, etc): full strength

Personally, I have used alcohol and even a cigarette lighter when nothing else was available.

By the way, bleach can be very corrosive to steel. When using bleach, oil your equipment at the end of the pruning day.

Sterilizing and sanitizing solutions have a life span. Dispose of these solutions at the end of the day and reformulate them again when needed. If there is a lot of pruning and equipment is particularly dirty, then sterilizing solutions will need to be reformulated more frequently. 

One excellent method that reduces disease transmission from a piece of equipment is air drying it.  Unfortunately, when you are pruning the cuts are made fairly rapidly and the blades never really have a chance to dry between cuts which increases disease transmission potential, particularly bacterial, viral and viral-like diseases.

How often should you sterilize equipment? Equipment should be adjusted, sharpened and sterilized at the beginning of a pruning day. If trees are healthy then there is no reason to sterilize her sanitize pruning equipment between cuts or between trees.

When you encounter a tree that is diseased or you are not sure if it does have the disease, I would recommend sanitizing between every cut to reduce the potential from spreading it within the tree.

Workers who are moving between properties must sterilize equipment between properties at a minimum. They should be taught that if a tree or shrub looks unhealthy, they need to sterilize between cuts. This is when a rag for wiping off debris and cigarette lighter that can fit into your pocket becomes handy. Any attempt is better than no attempt.

Root pruning. Sometimes I recommend pruning roots of plants. When cuts are made on roots of plants it is important to keep the pruning cut exposed to the open air for 24 to 48 hours before allowing it to come in contact with the soil again. This helps prevent disease transmission from the soil to the plant of soilborne diseases which are numerous.

Encouraging Monarch Butterfly in the Mojave Desert?

Q. I've been thinking about growing milkweed plants to help in the Monarch fight. Two varieties look worth pursuing Asclepias EROSA and SUBULATA. Any thoughts?

A. I grew up in the Midwest and in the path of Monarch butterflies migration routes to Mexico. In fact, as a boy I volunteered to monitor Monarch butterflies for a research study done in Canada back in the 1960's.

After moving to southern Nevada I have not seen any Monarch butterflies in the 30 years I've been here in the Las Vegas Valley. My understanding is there are two migration routes; one from the eastern population of Monarch butterflies and one from the Western population.

Map of Monarch butterfly routes

http://en.wikipedia.org/wiki/Monarch_butterfly_migration#mediaviewer/File:MonarchWanderungKlein.gif

The eastern population misses us completely in the Western population is pretty much restricted from us by the Sierra Nevada Mountains.

Encourage and sustain local populations. I agree with you wholeheartedly on encouraging our local populations of butterflies and moths. They had a lot of beauty and grace to our landscape and provide some pollination and a food supply. Instead of focusing just on milkweeds I think a diversity of plant material for attracting these insects might be important.

Be careful of pesticide use. Also, reducing or eliminating pesticide use in the butterfly garden area would be wise. There are a number of pesticides that are harmful including two that I recommend frequently to organic gardeners: Bt and Spinosad. When considering pollinators both of these insecticides can be lethal, in particular Spinosad to bees.

Always apply pesticides, if they must be applied, at times when these creatures are not active. This means the very early morning hours. Many of our moths fly at night so I would avoid applying pesticides at dusk if a major concern are night flying moths.

Further reading. I put together some links on general information on Monarch butterflies, moths and butterflies of southern Nevada and how to make a butterfly garden. I wish you much success.

Wikipedia on Monarch butterflies

http://en.wikipedia.org/wiki/Monarch_butterfly_migration

Donate to Wikipedia

http://wikimediafoundation.org/wiki/Ways_to_Give 

Threats to Monarch butterflies

http://www.flightofthebutterflies.com/conservation-preservation/

Butterflies of southern Nevada.

http://www.unce.unr.edu/publications/files/ho/2005/sp0525.pdf

How to make a butterfly garden in the southwestern desert of the US

http://www.dbg.org/system/files/253/original/Butterfly%20Gardens%208-11.pdf?1315954953

http://gardenoracle.com/butterfly_garden.html

Time of the Year for Holes to Appear in Trees

Q. I noticed that the woodpeckers have attacked our Palo verde tree. There are probably 60 holes around the truck and main limbs. The sap is running even though the holes are just under the surface - not deep. Any advice how to prevent further damage and do you think this can eventually kill the tree.

A. The only thing is exclusion and putting up some wire mesh to keep them from the trunk. They will still get into the lower limbs since it is hard to put wire mesh there.

Sapsucker damage to apple (above) and eucalyptus, aka gum (below).

I have seen our fruit trees attacked, the same ones, year after year and the trees still seem to be doing well. I know it causes damage but it seems to be not life threatening so I would let it go.

You could try some hot pepper sprays just before they begin damaging plants. Mark the event on your calendar. They are migratory so putting on some sprays might discourage them and force them on to your neighbor’s trees.

Imidacloprid and Bee Decline Linkage

Q. I don't like what I'm reading about Imidacloprid and wanted to know if there is a better insecticide that won't harms bees.

A. Trade names for this chemical name include Gaucho, Admire, Merit, Advantage, Confidor, Provado and Winner.This particular pesticide has a lot of problems and will probably be eliminated in the not-too-distant future because of these problems. Unfortunately, this pesticide is extremely good at what it does and fills a pest control niche that few other pesticides, if any, currently can fill.

We need other choices. The niche that it fills is a very effective borer killer that is systemic and for the most part gives you season-long control. Some of the same reasons it is so good may make it also dangerous to use. Even though the label allows for its use on fruit trees for example, I discourage people from applying it to those trees because it is systemic. I believe that any systemic insecticide has the potential to enter the food that we eat.

Method of application protects bees. Methods of application have a lot to do with exposure to bees. Those pesticides which are applied as a liquid or as a foliar application to the leaves and stems of plants have a higher probability of coming in contact with bees than the same pesticide applied as a soil drench. Soil drenches are liquids applied to the soil and rarely come in contact with bees.

Common products containing Imidicloprid.

Be careful of plants treated. However, this particular insecticide is systemic and can be transported from the roots of plants to the flowers that bees may visit. So in the case of this particular insecticide applying it as a soil drench may still be a problem for bees that visit flowers of plants that were treated with a soil drench. The larval form of many butterflies and moths rely on the leaves of some plants as a food source. Systemic insecticides applied as a soil drench may also be a problem for these insects.

Best use for this pesticide? If we are to continue to use this insecticide perhaps its best use might be as a soil drench on trees and shrubs that are nonflowering and are not used as a food source by anything that we value.

Alternatives? As for alternatives, I do not know one that is this effective for borer control. If we are talking about borer control then prevention is the key. This means preventing sunburn to these plants and keeping them actively growing and healthy is a partial solution.

As for other insect pests that it controls you have many alternatives. However, these alternatives will probably not be as persistent so you will have to apply them more often.

Whenever your focus is on protecting bees you must consider how toxic the chemical is toward these critters, avoiding applications when plants are in flower, applying foliar pesticides at very early morning hours or at dusk when bees have gone home, using pesticides which have a very short life after they are applied and are not persistent in the environment. And even more importantly we must begin to think about the use of pesticides as a last resort, not a first choice when there is a problem.

Pruning Japanese Blueberry to Encourage Growth

Q. I have 13 Japanese blueberry's they have been planted for quite a few years. They have grown tall but only one filled out from the bottom to top because of some shading. This shading is now gone. What can I do and when to stimulate the growth and hopefully have them fill out all over. 

Japanese blueberry picture from another reader.

 A. Severe shading can cause branch or limb dieback. Reduced light to branches can also cause leaf drop and poor growth on living wood.

What to do? Determine if these branches are alive or dead. If they are dead then all you can do is remove them back to the trunk or back far enough to healthy wood. Grasp these branches and bend them. Dead branches will snap like a dry or dead twig. Living branches will bend and not break as easily. If you bend a living branch back far enough of course it too will break so you have to be careful when bending them.

Wait and hope.If they are dead and you have pruned them back, all you can do is wait and hope that light reaching inside the plants will “sprout” new growth and fill in over time. If they are alive then do not prune them all the way back but cut off just a few inches of the ends just far enough to cut into living wood.

Dead branch of Japanese blueberry from another reader.

This might be one or two inches or six or more inches depending on where living wood is located. These types of cuts are called “heading cuts” and remove the terminal buds and will stimulate the plant to fill in bare areas.

When to do this? Do this in about early to mid-February next spring. Fertilize the plants at that time with a tree and shrub fertilizer or even a lawn fertilizer and give the plants a two or three deep waterings with a hose a few days apart. The water from the irrigation system will move the fertilizer into the root area. The fertilizer should be a high nitrogen fertilizer. It would be helpful to give them some iron applied to the soil as well at the same time.

Again More Rabbit Damage!

Rabbit damage to chard. Picture courtesy of another reader.

Q. We live in Sun city Summerlin the rabbits are eating our plants Star jasmine, silver spoon yuccas, and even canary island date palms lower leaves. We have tried Shake-Away Fox and Coyote Urine Granules and scaring them but nothing has worked. Any suggestions or tips would be helpful.

A. These kinds of products are deterrents. Once they are hungry those will not stop them and they will eat even less desirable plants. The only real way to get a handle on them is exclusion (fencing)
which can look horrible. Planting less desirable plants (Arizona fact sheet found on the link below) will help push them to more desirable plants they can find in the neighbors yards.

Rabbit resistant plants Arizona

http://xtremehorticulture.blogspot.com/2013/10/rabbits-problem-fencing-and-rabbit.html

http://xtremehorticulture.blogspot.com/2013/07/how-tall-should-wall-be-to-keep-out.html

http://xtremehorticulture.blogspot.com/2013/10/rabbits-do-not-jump-over-fences.html

http://xtremehorticulture.blogspot.com/2013/11/pictures-are-classic-rabbit-damage-to.html

http://xtremehorticulture.blogspot.com/2014/12/damaged-cactus-edges-probably-rabbits.html

Fire Barrel Cactus Adds Interest to Desert Landscapes

Care and Pruning of Pyracantha and Honeysuckle

Q. I am writing and enclosing photos of my pyracantha and honeysuckle. I cannot find info on the issue/treatment. A friend suggested I email you after reading the LVRJ column.

A. Thanks for the pictures but they were not very helpful without more information. Let me tell you what I know about these plants and maybe that can help.

Both of these plants grow well in our climate in a mixed, non-desert landscape. They are not desert adapted or desert plants so they will not perform well with rock mulch.

Over time, they will perform better using wood mulch on the surface of the soil.

They should be irrigated at the same time as other non-desert plants. They should be on an irrigation valve that provides water as frequently as other nondesert trees and shrubs.

Most landscape plants require at least one fertilizer application each year in the spring or late winter. You can apply these spring fertilizers into March. Any general landscape, tree and shrub fertilizer will be good.

Pyracantha occasionally develops yellowing due to iron chlorosis so an application of EDDHA iron chelate to the soil at the same time as the fertilizer would be advised. Apply both within a

foot of drip emitters on top of the soil. The iron chelate needs to be covered with mulch.

Pyracantha has a history of borer problems, particularly if it is planted in a southern or westerly exposure in rock mulch with lots of heat and intense sunlight. Borers can be active in the plants and the plant can still appear healthy for one or two seasons.

After a season or two of borer attacks branches turn brown and begin to die back. They normally die back to where the borer damage while the rest of the undamaged plant below this remains green. Prune these dead branches out and let the plant regrow from these areas.

Pictures from reader

Because of the dead branches, the interior wood and trunk will receive intense sunlight. This intense sunlight increases the chance of sunburn to larger limbs and the trunk. This sunburn damage attracts boring insects (borers) to those locations.

Borer damage in purple leaf plum

For this reason, shade from the canopy on the interior wood of the plant is extremely important. Many woody plants in the rose family, which includes Pyracantha, are subject to damage from intense sunlight due to their thin outer bark.

Most of our fruit trees are also in the rose family and are subject to sun damage and borer
problems. Pruning should be pruned to maintain a moderately dense canopy. A canopy which is not so open provides filtered sunlight to the interior of the plant and reduces sun damage. You don't want it pitch black inside the canopy but you do want filtered light, not intense sunlight, for any length of time.

Honeysuckle is a good vine to use here. However, it tends to get woody at the bottom as it gets older. This woodiness at the base can be managed by pruning it correctly. Woodiness at the base is promoted when the vine is pruned only at the top. Several years of pruning the top results in an unattractive plant that is mostly wood without much foliage.

When pruning this plant this winter, instead focus pruning efforts on the area close to the soil surface. Find large stems originating from this area and remove one third of this older wood close to the ground. This removes a lot of plant material from the vine but promotes new growth from the pruned stems.

Limb dieback of peach due to borers

These types of pruning cuts encourage new growth from the base of the plant. Next winter remove one third more at the same location and you should be back on track and reversing the aging of this plant, making it more juvenile. Focus your pruning efforts closer to the ground.

Can We Plant in December and January?

Q. We are re-doing our whole front yard and just finishing up the drip lines. Is it too late in the season to put in new plants now?  We are planning on lantana, society garlic, red yucca, Mexican bird of paradise, and some deer grass.

A. We have entered the coldest part of the winter now in Las Vegas. We can expect temperatures to reach anywhere from mid teens to mid-20's late in the night depending on where you live. All of the plants you mention, except red yucca, could be damaged if you plant now. Larger, cold hardy trees and shrubs would still be okay to plant. Wait until after the coldest period of winter has passed to plant, about the first to the second week of February.

After you plant you should consider applying mulch to the soil surface surrounding them just to give them a little bit more protection. Whenever you are planting trees and shrubs into residential soils you want to mix good quality compost in the backfill surrounding plant roots. Use an equal amount mixed with the backfill surrounding plant roots.

Which Is the Best Pomegranate Variety?

Q. Which varieties of pomegranate are good to grow in the Las Vegas area?

Wonderful pomegranate grown in  Las Vegas

A. Southern Nevada is a good pomegranate climate, similar to the climates where pomegranates originated in south central Asia, Persia, Pakistan, Afghanistan and India.In areas: or than this pomegranates can freeze back. In warm but humid climates pomegranates have disease problems that we never see.

In the United States we have a wide selection of pomegranates available to us that have been collected from throughout the world. Some of the newer selections may be cold sensitive in parts of our Valley. I would stay away from unknown varieties unless you want to experiment.

Beautiful yellow pomegranate with red arils grown in Tajikistan

For the most part, all of the pomegranates available commercially do well. Of course the flagship pomegranate variety is ‘Wonderful’ with its beautiful outer and inner ruby red color. In actuality pomegranates come in a wide range of colors from dark purple to nearly black all the way to lemon yellow and off-white.

Pomegranates come in a wide range of colors on the outside but the inside of the fruit can vary from dark red to pink to white and from seeded to nearly seedless (soft seeds)

You will not go wrong with varieties such as ‘Sweet’ or ‘Eversweet’. A local favorite, sometimes referred to as seedless is ‘Utah Sweet’, a selection from ‘Sweet’. A variety from the former Soviet Union receiving rave reviews is ‘Parfianka’.

Other varieties I have liked include ‘Sharps Velvet’, ‘Red Silk’, ‘Pink Satin’ and ‘Grenada’. One variety I have been less than thrilled about is ‘Ambrosia’, and early producer but no flavor. I have seen no winter damage on any of the varieties I mentioned above.

What Causes Leaf Browning in Lilac?

Q. Since late September my five foot lilac planted on the West side of the house has been showing signs of stress. The lilac made it through the summer fine and all green but has recently shown browning of the leaves despite continuing to bud.  I read that fertilizers are not recommended or necessary but I am tempted to try.

A. Both common and Persian lilac grow in our climate. They will not do well in a rock landscape. They prefer soils higher in organic matter. If they are surrounded by rock, they will begin to decline in about 3 to 5 years, leaves will begin to scorch, you may see some branch die back, leaf drop and a reduction or no flowering at all.

Some varieties of lilac perform better here than others such as the early bloomers. An old reliable common lilac is Lavender Lady hybrid one of the first low chill lilacs produced. This particular variety requires less chilling and blooms well here. Another variety to consider might be Excel which also have a lower chilling requirement and is a very early bloomer. I would proceed with caution on low chill, late bloomers such as Angel White, California Rose and Esther Staley unless someone has had a proven record of good blooms and color.

This could be a location problem. A Western exposure is too hot for it. It likes sunlight but not combined with intense heat. It is best to have it in a location protected from late afternoon sun.

But I totally disagree that lilac doesn't require fertilizer. It not only requires fertilizer once a year applied after blooming but, under desert conditions, benefits from compost or organic amendments added to the soil. Lilac will perform well with some unamended arid soils but our desert soils in Las Vegas are just too low in organic matter. Lilac likes a richer soil than unamended desert soils can provide. It likes compost, wood chips as a surface mulch and fertilizer.

Can I Plant My Gift Hydrangea Outside?

Q. My kids sent me a hydrangea for the holidays.  I know I have to keep it as a houseplant.  When I lived in New York, mine were huge outdoors. What do I need to do keep them alive and thriving?

A. Hydrangeas are not meant for planting in our climate and soils. Hydrangeas given as gifts are like poinsettias; intended to be grown in greenhouses for a one-time gift event. But what the heck, give it a shot!

There are some varieties of hydrangeas that are more suitable for growing outdoors than others. Western Sunset Garden Book has recommended varieties you can try. If you are lucky enough to have gotten one of these varieties as a gift then you may have a fighting chance of keeping it alive.

They need a bright location on the north or east side with filtered light. Add compost to the soil at the time of planting. The plants need an organic surface mulch that decomposes, enriching the soil, such as wood chips. It should be fertilized with an acid fertilizer every 6 to 8 weeks.

If you want to go whole hog on this plant then get some aluminum sulfate and apply it to the soil when you plant and in early spring. Aluminum sulfate does a better job acidifying the soil than sulfur. Acidifying the soil helps keep the flowers of vibrant blue color.

You are fighting an uphill battle on this one but if you really want it to work you must spend time and money on this plant with soil preparation, mulch and specialized fertilizers such as aluminum sulfate.

Otherwise, I would not bother and enjoy it for what it was intended; a gift on a special occasion from loved ones.

What is Causing Citrus Leaves to Yellow?

Q. What is causing the leaves on my lemon tree to turn yellow?  This has been happening gradually all year.

Readers lemon leaves

A. Leaf yellowing of citrus is caused by any of these problems or in combination: high light intensity, micronutrient deficiency such as iron, irrigation and drainage problems and salinity. If the yellowing occurred during the winter and it was more of a bronze appearance then I would say it was due to winter cold.

Looking at the picture you sent, some of the leaves have leaf tip burn. That could be caused by salinity or a lack of water. It is possible it could also be too much water or poor drainage but I don't think this is the case unless you are watering it several times a week.

Without more information I am guessing it is a combination of high light intensity, micronutrient deficiency and possibly salts. If the leaves were more “bronzy” looking I might also conclude it could be high light intensity if it is in a location with lots of reflected light.

Yellowing of citrus leaves due to high light intensity

Flush salts from the soil. Apply a large volume of water to the irrigated area under the tree to flush salts that might be causing a problem. Do this two or three times over a period of a few days then revert back to normal irrigations.

Water no more than every ten days right now. Make sure the volume of water is sufficient to wet the soil 18 inches deep. When new growth resumes, resort to irrigating more often but this time of the year irrigating 10 days apart should be adequate.

Unkinown nutrient deficiency of citrus but probably manganese or iron. Since iron deficiency is common in the Las Vegas Valley the KISS principle tells us to treat for iron

If there is rock surrounding the tree, pull it a distance of 3 feet away from the trunk. If wood mulch surrounds the tree, you do not need to pull it back. Make sure wood mulch does not contact the trunk of young trees. Keep wood mulch 6 inches away from the trunk.

Next, apply iron chelate containing EDDHA beneath the tree in January near a source of water. Cover the iron chelate with wood mulch to keep it out of the sun or make sure it is placed beneath the soil surface.

Magnesium deficiency of citrus

Next February or after fruit set apply a normal amount of fertilizer. Organic fertilizers are best. You should see a change in the color of the new leaves next spring during growth.

Top 10 Questions of 2014

These are the top 10 questions of 2014. Each question is linked back to its answer. Click on the question and it will take you to my response.

#10 Vitex Water Management Affects Blooms and Growth

#9  Why Are the Leaves of My Locust Tree Turning Yellow?

#8  Warty Growths on Tree Limbs Solved

#7  Get Ready for the Leaffooted Plant Bug Invasion

#6  Stink Bugs Attack Residents and Car in Henderson Nevada

#5  What Your Vegetables Need Now

#4  Determining the Correct Sized Drip Emitter

#3  Vegetable and Herb Planting Calendar for Las Vegas

#2  Puffballs and Other Mushrooms Common to Desert Landscapes

#1  What Is a Good Patio Container Fruit Tree

What Causes Brown Leaves on Yucca?

Q. Why are the tips of my yucca leaves turning brown? 

Brown leaf tips on yucca. Can be from soil or irrigation problems.

A. This is pretty common on yucca in our climate and soils unless they are grown in filtered sunlight and the soil has been prepared well before planting. They always tend to have brown tips. In the case of your plant, judging from your picture, it does seem excessive.

When we see brown tips on the foliage of desert plants it usually means a watering problem, a soil salt problem or lack of drainage.

This particular yucca is native to the Chihuahuan desert so infrequent irrigation is critical to its health. Most of the soils in the Chihuahuan desert are better than our landscape soils created by the builders of our homes.

Regarding your irrigations, compare your watering with how these plants might be watered in their natural habitat. This is a guideline for how you should water. They won’t need watering that often so if you are watering more frequently than every two or three weeks in midsummer, I would suggest this is too often.

If this plant is on the same irrigation circuit as other landscape plants, and these other plants are not a desert plants, then I would suggest the plant is being watered too often.

The volume of water you give the plant is not as critical as the frequency it receives water. In other words, you can give it a large volume of water and not hurt the plant as long as you wait long enough before the next irrigation. Giving large volumes of water may waste water but it seldom keeps the soil too moist for the plant between irrigations.

If this plant is watered too often, remove it from that irrigation circuit and water it by hand every few weeks. It will like a couple of deep winter irrigations, a spring irrigation, a couple of midsummer irrigations and a fall irrigation and that's about it.

If the applied water is close to the trunk, then the trunk could be rotting. Keep frequent irrigations away from the trunk. However, it is okay to water in a large basin beneath the plant if it is done infrequently.

If there are other plants around it, it is probably getting enough water from its neighbors. But I would still give it an occasional drink to be on the safe side.

Can I Apply Iron in the Winter?

Q. I have a dwarf lemon tree with many yellow leaves. Can I add iron at this time of year (December)?

This is not citrus but it is iron chlorosis. You can tell from the yellowing of the leaf while the veins remain green and appearing on the newest growth. It is possible to confuse it with manganese deficiency easily.

A. If you apply iron this time of year (December) it is best applied as a foliar spray rather than to the soil. If the leaf yellowing is not extensive you could wait until spring. Leaf yellowing reduces a plant’s ability to capture sunlight and produce energy to maintain its growth and health.

Iron chelate made for applying mixed with water. 

If you want to correct it now, you must apply iron to the leaves as a liquid or foliar spray. It is best to use an iron chelate mixed with water and add about 1 tablespoon of white vinegar if you use tap water to reduce the alkalinity. If you use distilled water, you will not need the vinegar.  To this water add the appropriate amount of iron chelate listed on the label. You should add a wetting agent to help the spray penetrate the leaves.

You can make your own wetting agent by using a liquid detergent like Dawn or Ivory Liquid at a rate of about 2 teaspoons per gallon added to the finished spray mix. It is not as refined as a commercial wetting agent but it will do the job.

A very safe wetting agent for better leaf penetration

You would apply this mixture of water, chelate and wetting agent to the leaves immediately after mixing it until the spray runs off the leaf surface. Let the leaves dry and repeat it a few days apart or until you see the leaf color change from yellow to a darker green.

Foliar sprays like these may require several applications to get the results you desire.  Citrus leaves have a very waxy surface and are difficult to penetrate with just plain water. If you use tap water then each time you prepare a new spray you should adjust the alkalinity of the water with vinegar and add a wetting agent.

Foliar sprays should always be freshly made, applied immediately and not stored for any length of time. Unfortunately homemade iron liquids, unlike commercial sprays, do not store very well. It might be cheaper in the long run to buy the liquid iron spray already made and make the application.

It is also possible citrus leaf yellowing could be a magnesium or manganese problem. Liquid iron sprays will not correct problems due to magnesium or manganese.

Radishes Are the Perfect Winter Vegetable for Beginner Gardeners

Radishes are the perfect winter crop for the beginner gardener in the ground, raised beds or containers. They are easy to grow, will germinate at very low soil temperatures and will mature for harvesting in as little as 30 days. Don't plant them too deeply and to speed germination cover with some clear plastic to keep the soil warm. Remove the plastic after you've seen them germinate.

Space the seed in rows or in blocks so that the seed is about 1 to 2 inches apart from each other. In our Las Vegas climate you should be able to get 5 to 6 crops during the fall, winter and spring seasons when they are the sweetest.

Find some hybrid varieties which will reduce the heat or spiciness if you don't like that. The tops can be eaten in a salad or cooked as greens just like mustard greens. The oil that you use in cooking greens has a big impact on the flavor of cooked greens.

French breakfast radish after 30 days

Spacing of radish seeds. If radishes are too close together they will not produce large bottoms.

Brown Ugly Space Alien in the Garden

Recently I found this brown space alien into one of our raised beds. This is the pupa, or resting phase, of the tomato hornworm. This is the stage of development between the worm or larva and the adult hummingbird or sphinx moth. This insect is a voracious feeder of all garden plants but particularly tomatoes, peppers, eggplant and even grapes!

This insect will overwinter in this stage and emerge again in the spring as the adult hummingbird moth. It will find a mate by flying at dusk and lay eggs on plants that it likes to eat. The eggs will hatch into a miniature hornworm and voraciously grow into the much larger version.

Hummingbird or Sphinx moth

Right now you can dispose of them. But later in the spring after planting you will want to protect your plants with either Bt or Spinosad.

Bt can be found under the names of Dipel or Thuricide as well.

One of the names for Spinosad. Check the ingredients

Delay Pruning Grapes Until Very Cold is Past

Q. I usually prune my grapes when I do the roses but would like to get a jump on it this year. Will I do them any harm if I prune them now (December)?

A. You can do it but I worry a little bit about possible freezing damage if these are winter tender grapes and desiccation. Some grapes are less cold hardy than others. For instance, Thompson seedless has some wine grape heritage (vinifera) and tends to be less cold hardy than some other table types.

I have noticed in our desert climate that we can also get winter desiccation (drying out) in windy locations. Those grapes which are pruned to spurs usually leave only one or two buds which means the spur may only be one half inch long after pruning. If we lose this half inch of growth from winter cold or desiccation, then we have lost our crop for the season.

I usually delay it until almost the first week in March when buds are starting to swell. By delaying it I can prune out the dead wood that occurs during the cold winter months and focus on the stuff that is still alive. I would wait.

Swarming Bugs; Ants or Termites?

Q.  We were out in our yard last weekend putting up decorations when we noticed small bugs flying up out of our yard. They were thick groups of them coming out of small holes that looked like grains of rice clumped together in bunches. There had to be thousands of them. The "exodus" lasted for about an hour and then it was done with no sign they had been there.  Can you tell what they are?  Are they harmful?  Do we need to do something to get rid of them?

Flying ants or termites. The length of the wings suggests termites but a visual check of the bodies and antennae need to be done.

A. These look like winged ants or possibly winged termites. It was difficult to tell from your picture. They both swarm in identical fashions. The ants are just a nuisance. If these are termites then you may have a problem.

You need to catch some of these insects and look at their body shape, antennae and length of their wings. Ants have a constricted waist or segmented body parts. Termites do not have these segmented body parts and body parts are not as easy to distinguish. 

I have provided a link on my blog for you to follow or you can type the following into your search engine that will help you identify the difference between the two different insects. 

How to tell the difference between ants and termites

If you believe these are termites contact a reliable pest control company and schedule a follow-up.

Follow the link below or on my blog to read information about flying ants from Colorado State University. More about flying ants

When Should I Winter Prune Flowering Plants?

Q. I have some bushes and shrubs in my backyard that still seem to be blooming. How do I know when they are ready to be trimmed back?

A. Sometimes we have to prune them back to make way for new growth in the spring. For small plants that get a lot of woody growth at the base, let them go through the winter and trim them back after all of the very cold weather has passed this winter. That is usually by mid-February.

Lantana after winter pruning. This was actually left too long. Prune closer to the ground. After pruning, this is what you will look at until February.

Pruning of ornamentals is all about appearance. If it looks bad to you, go ahead and prune it back. You will not hurt the plant. My major concern about pruning too early is the possibility of freezing damage and creating more work for yourself. If you prune now and we get more freezing weather then you will have to prune a second time.

Waiting until the end of the coldest part of the winter avoids pruning a second time. But if you like to go out in the yard and tinker, prune when you need to. It won't bother the plant.

Harvest Oranges Before a Hard Freeze

Q. After 6 years, I am finally getting  oranges. They are turning orange and I have been told not to pick them until mid January. Is this right or can I pick them now (mid-December)?

A. Different varieties ripen at different times. I would sample one now and if it tastes good to you then harvest the others at the same maturity. If it is not yet to your liking then wait a bit but if temperatures drop to the mid-20’s then the fruit might freeze. In the Las Vegas area we get our coldest weather NORMALLY from mid-December to the end of January.

Play it by ear a bit right now but normally they would be ready right about now. You do not want to wait too long because fruit remaining on the tree can interfere with new flower production.

I copied and pasted this citrus calendar from the University of Arizona pdf document you can download from HERE. These are the approximate harvest dates (this is for Maricopa County, aka Phoenix area). We are a bit colder so harvest times can be a bit later. However for areas like Laughlin and Bullhead City they would be on the mark.

Note: I am recommending citrus in the Las Vegas area in only warm microclimates or protected from winter cold and winds.

The chart below I copied and pasted from the University of California Riverside pdf document you can download HERE.  This tells you the critical temperatures where you might lose different parts of the tree (flower buds, blossoms, green fruit, ripe fruit).

Will Buffalograss Grow in the Mojave Desert?

Q. Will Buffalograss grow in the desert?

A. Buffalograss grows perfectly well in the Mojave desert. The major problem is finding a source for it. I would not start it from seed if you want a good quality lawn. The best method would be to use sod but without a source of sod locally, you could have plugs shipped in from a reputable supplier.

Buffalograss can make a good quality lawn if you started from sod or plugs but not from seed..

Buffalograss is native to our dry grasslands and prairies of the United States. Like Bermudagrass and zoysia grass, it is a warm season grass which means it will become dormant or go to sleep during the winter months. It is best planted when soil temperatures have begun to warm in the spring or very early summer.

Preparation of the soil is very important for good establishment. Plugs are normally at least 2 inches in diameter and spaced 12 to 24 inches apart in the lawn area. Because Buffalo grass is a sod forming grass it fills the bare soil between plugs with stolons or surface runners. With good management the lawn area should be completely filled before it gets cold in the fall.

This is a bit controversial but research in Arizona has demonstrated Buffalo grass to use about the same amount of water as Bermuda grass but it does not require the fertilizer or the same level of management.

A reputable supplier out of Nebraska is Todd Valley Farms. Give them a call and talk to them if you are thinking about Buffalo grass.

Can I Grow Persimmon From Seed?

Q. I had a couple of persimmons from a friend's tree in California. Can I plant these seeds from this fruit and if so do the trees thrive here?

A. Yes, persimmons will grow in the desert with a little bit of extra care. Our desert soils must be amended with compost before planting. After planting, persimmons will perform best with a surface mulch of 3 to 4 inches of wood chips. Persimmons perform very well if you fertilize with compost once a year.

Persimmon leaf size with organic fertilizers like compost applied to our desert soils.

You can grow persimmon from seed easily but these trees will not be exactly the same plant as your friend’s. A tree from these seeds might have better fruit or the fruit might be worse.

To germinate, persimmon seed must go through about two months of cold, wet conditions,Similar to the conditions it would find in nature. In nature the fruit matures in late fall or early winter and drops to the ground in a layer of natural surface mulch or debris. In this surface mulch it spends the cold winter. In its native environment this surface mulch would stay relatively moist compared to our dry desert winters. 

Hachiya persimmon grown in the desert that is nearly mature. At this stage the seeds can be harvested but the fruit will not be quite at its peak of ripeness and will still be astringent.

You can simulate this by using a refrigerator. Refrigerator temperature is fine but the seed should be kept moist but not wet. These conditions remove inhibitors in the seed coat that may keep it from germinating. Make sure the seed is clean and pack them in ever-so moist sand before putting them in the fridge. This should not be in plastic bags but something that can "breathe" while in storage. You need to moisten the seed's environment periodically.

After the two months and freezing temperatures have passed, you can plant these seeds directly into amended soil in the garden area or in a container.

Alternatively, plant them directly into amended soil in the garden or container, moisten the soil, mulch it with 2 inches of wood mulch and water about once every 3 weeks during the winter. They should germinate in the spring in the spot where you planted them when the weather warms.

Saving Bougainvillea From Freeze Damage

Bougainvillea summer time

Q. While most of our bougainvillea are in large pots which we bring indoors for the winter, this year we planted one in an above ground planter built around the Jacuzzi. What should I do to help it survive the winter without having to dig it up and transplant it again in the spring?

A. Your bougainvillea will have a better chance of surviving the winter planted in the ground than it will planted in a container. However, expect it to be damaged this winter unless you are willing to apply heat to the area where it is planted and cover the plant all the way to the ground.

Bougainvillea that has frozen back during winter

If left unprotected, your bougainvillea will freeze to the ground as soon as temperatures drop below freezing. If temperatures dip quickly below freezing and rise above freezing in a short period of time, damage will be light. If temperatures dip below freezing and stay there for a while, the entire top of the plant above ground is likely to freeze and die.

The death of the top of the plant is not necessarily a big problem. The dead parts can be pruned back close to the ground and encouraged to regrow in the spring. My major concern is protecting the base of the bougainvillea, near the soil, so it can regrow.

Some inexpensive insurance is to pile several inches of mulch around the base of the plant just before it freezes. This wood mulch acts as an insulator which protects wood at the base of the plant from dying. Of course if temperatures get unusually cold for long periods, it is possible to lose the entire plant. But in most winters this will not happen if mulch is used.

In mid-March prune out any damaged plant parts back to healthy wood. Fertilize the plant with a high nitrogen fertilizer and water deeply. After it has re-grown significantly, apply a phosphorus fertilizer either to the soil or spray and liquid on to the foliage.

Protecting Plants from Freezing Weather