Brown Spines on Agave stricta

Q. A quick question about a newly planted Agave stricta. Within 2 weeks of planting the spines have begun turning brown from the tips down. Do these plants generally brown out in the cold or is this one dying? It is a 15 gal plant - purchased from a local cactus nursery. It had some brown on a few stems shen purchased, but not like this. It was planted according to the instructions from the nursery with a sand/soil mix at bottom and sand around the perimeter.

Click here to see what Agave stricta looks like

A. I had to look up that particular agave because I did not know it. There is some information about it at the San Marcos nursery website

http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=84

It is found growing in southeastern Mexico in its native habitat at about 5000 feet from what I could find. San Marcos nursery says it will handle temperatures down to at least 20° F. This is for Agave stricta ‘Nana’ so I am wondering if this is what you have or not.

A. stricta is confused with A. striata a lot because they look almost identical. This particular cactus may benefit if it's not placed in a location where it receives very hot direct sunlight in the afternoon. It sounds like it is a little bit delicate perhaps because of where it grows and its elevation.

Click here to see what Agave striata looks like

I am thinking you may have one of two or three things going on with yours. I don't think it's temperature. If this cactus was growing in a shaded or semi shaded area and then placed into an area that receives a lot of direct sunlight in the late afternoon it's possible that it could be sun damage.

How you planted this cactus sounds fine but if you are watering it too often, even with good drainage, this could also cause problems. When water is scarce it relies on internal storage of water. During the summer I would not water it more than every three weeks if you are planning to push some growth.

If you're happy with that size, you can water it less often than that. It is also possible that the soil mix that was used could have been a little too saline. Flush the soil with several gallons of water a few times to remove any excess salts if you think this might be a problem.

But I do not think it is a temperature damage but more likely to be sun damage or damage from irrigation. During the winter you should be able to water only once or twice during the entire winter.

Further thinking, it is POSSIBLE it could be a salinity problem. There are soil mixes out there that use sands with lots of salts in them and they are not washed sands. Wash plenty of water through the soil where you planted a couple of times a few weeks apart to reduce salt problems. Now is a good time to do that because temperatures are cold and tolerance to lots of water in the soil is much higher in plants during cool or colder weather.

Acacia longifolia Tolerance to Cold in the Mojave Desert

Q. Would Acacia longifolia do okay in the Las Vegas area?

A. San Marcos Growers reports cold hardiness down to 20F so it will take temperatures similar to Myers lemon, a fairly cold hardy citrus.

Click for A. longifolia at San Marcos Growers 

It is possible it might have dieback during some extremely cold winters but it should re-sprout easily from its base once it has established for one season. Like any Acacia I worry a little bit about allergies from its pollen. It is a rather large plant usually grown as a shrub but I think you could train it into a small tree fairly easily. It should handle our soils with little problems just make sure that you amend the soil at the time of planting with compost.

Anyone with experience with this plant?

Planting Vegetables from Seed in January

I have seen garden editors right that there is very little to do in January. How wrong! This is a very busy time of the year for vegetable production. In our cold desert climate with warm days and cold nights some of the best vegetables of the year are produced. Cool and cold winter temperatures slow growth of plants which concentrates flavors and reduces bitterness in many of our cool season vegetables.

Germination from seed. As long as temperatures are warm enough during the day, seed germination of cool season vegetables may take longer but they will germinate if the soil is warm enough. Loose, dark, fluffy soils are warmer than heavy soils. Work in enough compost so that the soils are no longer compacted. Warm air during the day must be able to enter the soil through loose pores to warm it.

Select vegetable seed of known varieties that have performed well in the past or have been recommended to you by others who are good gardeners. Don’t use varieties of seed that are unknown to you unless you just want an experience and don’t care about the end result.

Know the temperature of your soil. This is important because diseases that are dormant in the soil may affect some vegetable varieties if the soil temperature is borderline for them. Beans are a good example and may fail due to root diseases if planted in soils that are too cold.

 

Use this soil temperature guide for vegetables

Prepare the area to be planted with seed with a high phosphorus fertilizer of your choice. Triple super phosphate is a good choice for conventional gardeners. Bone meal, bat guano, mushroom compost are good choices for organic gardeners.

Cover soils to be planted with clear or black plastic to warm the soil. I prefer clear plastic. Cover the soil with plastic two or three days before planting. Pin the edges of the plastic to the soil. Cover the edges of the plastic with soil so the wind does not lift the plastic. Just before planting cut slits in the plastic where seed is to be placed and leave the plastic on the soil surface until plants have germinated or longer.

Pre-germination of vegetable seed initiates seed germination. Pre-germinating the seed is wetting the seed long enough for a long enough period so the seed absorbs water. This is the first step in germination. The seed is kept in water at room temperature for 6 to 12 hours. The seed is then removed from the water and the surface dried in the air or with paper towels. The seed should be planted as soon as it is dry enough to plant.

Planting depth of seed is related to its size. Very tiny seeds are placed on the surface and covered lightly with soil. Larger seed are planted in the soil to a depth twice its diameter.

Fruit Tree Pruning Workshop in Twentynine Palms January 9

On Saturday, January 9, 2016, I will be at the Twenty-Nine Palms Inn in Twenty-Nine Palms, California, to present a fruit tree pruning workshop. I will also be discussing how to apply fertilizers and what kind and pest control operations that should be performed this time of year. The workshop will begin promptly at 9 AM. I will bring along some fertilizers for fruit trees and EDDHA iron chelates from Viragrow in Las Vegas for those interested. Contact me if you need me to bring along anything else that might not be available locally.

Fruit tree workshop presented last year at the Twentynine Palms Inn

Fan Palms Yellowing and Browning

Q. I have three mature California fan palms, aged at least twenty years, planted quite close to each other and located in Mesquite, Nevada. Two or three years ago, one showed signs of early leaf browning and soon died. Now leaves of others are quite yellow but stems and new growth at the top of the tree is green. I'm afraid they are going the same way as the one that died! Disease?

Yellowing palm leaves of the reader

A. I do not think the yellowing and scorching is directly related to disease. I think it is primarily a soil or plant nutrient problem that will not be solved simply by adding fertilizers. Irrigation might be part of the problem IF the trees are watered too often. In your particular case, I think several things may be going on at once.

I’m a big proponent of soil improvement when planting anything in our desert soils. In Mojave Desert soils, and soils brought in as fill around homes in housing developments, soil improvement at the time of planting is an absolute must even if you are planting cactus.

Desert soils are usually very low in organic matter like this soil. The light tan color of the soil is an indicator of a very low percent of organics in the soil.

If your soil is tan colored or very light brown, there is zero organic matter in that soil. Palms are typically planted without much consideration for any kind of soil improvement. They are planted in tiny holes, the roots surrounded with very little if any improved soil. Once planted, the soil surrounding the plant is covered with rock mulch.

In this type of soil environment roots suffocate and die over time. If they don’t die in the first couple of years, they have a great deal of difficulty taking up the proper nutrients from the soil even if fertilizers are applied. They become unhealthy.

The plants react to this poor soil environment by turning yellow. It’s not a disease caused by disease organisms directly but the plant color indicates they are in poor health.

To correct this problem, add organic material to the soil surrounding the roots and improve water drainage and movement of air into the soil. Until this is done, you will see very little improvement to these plants just by adding fertilizer.

In the past we used a technique called “vertical mulching”. It is no longer talked about much anymore but it was effective. Vertical mulching created vertical holes to a depth of 2 to 3 feet around the plant in the root area. These vertical holes were filled with improved soil.

Read about vertical mulching here

Vertical holes were created using a high-pressure watering device or a post hole digger. Pull back the rock mulch where you are going to create vertical holes a foot or two from the trunk. Create the holes using a post hole digger or water from a high-pressure nozzle to a depth of 2 to 3 feet. Be careful of irrigation lines.

Fill these holes with a 50-50 mixture of the soil you took out of the hole mixed with compost, minus any rocks larger than a golf ball. Create a minimum of four holes around these trees. Use these spots in the future to add fertilizer once a year. Apply more compost on the surface to further improve soil at the surface and put back the rock mulch.

Make sure plastic is not on the soil surface surrounding the plants and under any mulch. Plastic on the soil surface can create similar problems.

What To Do To Fruit Trees in January

Class in 29 Palms in 2014

What should you be doing with your fruit trees now?

• Finish your fruit tree pruning before February 1
• Fertilizing fruit trees
• Controlling pests

Thanks to Viragrow for letting me use pictures of their products.

Fruit tree pruning. I gave several classes on fruit tree pruning in December. I will be giving is in Twentynine Palms, California, on Saturday, January 9 beginning at 9 AM at the Twentynine Palms Inn. You can read about it on their blog soon or on my blog.

The major topics I covered included size control and improving fruit production. I divide fruit tree pruning into two operations for those just learning how to prune fruit trees; first of all control the size of the tree and establish its general architecture or structure and secondly prune to improve fruit production.

Fertilize fruit trees in our climate any time in January before the first week in February or before the signs of new growth if you are not in our climate. If you are late by a couple of weeks you can still do it. Use conventional fertilizers or compost. 

Use any fertilizer that is designated as a fruit tree fertilizer. In a pinch, you can substitute a rose fertilizer. Follow the label directions. 

If you were in my class, I would show you how to "read" a tree to determine how much fertilizer to apply. If you don't know, follow established guidelines that you trust. You can apply it on top of mulch or pull the mulch back and put it on top of the soil, then replacing the mulch. 

Make sure that you water it in enough to get the fertilizer in contact with wet soil. That last statement, in wet soil, is very important. Fertilizer cannot move to the roots if it is not in contact with water. 

Example of a dormant oil
available from Viragrow

Be careful how much phosphorus, the middle number, you apply. Phosphorus can hang around in soils a long time and it can build up concentrations if you aren't careful. Apply it only once during a growing season.

Controlling pests. Applying a dormant oil at least once, if not twice, during the winter is a very important preventive pest control application. It is aimed at aphids, scale insects, spider mites and a few other general pests that might appear this coming growing season. 

It is primarily aimed at "suffocating" these insects so it is important to apply it on a warm day with no wind. It is best applied by high pressure pesticide application equipment. However if you are using a backpack sprayer or other pressurized sprayer keep the pressure as high as you can during the application. This will help the oil cover as much surface as possible without leaving any gaps. 

Solo backpack sprayer

Low-pressure equipment or hose and sprayers "spit" out the oil which makes for a very uneven application and wastes a lot of the dormant oil. Dormant oils for homeowners are nearly always lightweight summer oils that are much less dangerous to plants than some of the winter oils applied in decades past.

Don't spray unless you have a problem or you had a problem last year and you're trying to get a jump ahead. 

Mature leaf footed plant bug

A prominent pest on fruit and vegetables last year was the leaf footed plant bug.Your landscape right now. Look for the adults that will be ready to lay eggs on your plants as soon as it is warm and they have some surface area. 

They will most likely hangout right now on broadleaf evergreen trees such as bottlebrush. They can see you coming and will move away from you as you approach the tree or plant. 

The adults have wings so they will be flying in from neighbors when temperatures start to warm up. Sprays that contain pyrethrin or the synthetic pyrethrins are a good choice on these critters. 

As a last resort, Sevin insecticide will control them but use that conventional insecticide when you have exhausted other possibilities such as oils, soap sprays and pyrethrin products.

I have a lot more information but you have to start asking questions if you want it.

Be Careful of Wildflower Seed in Primitive Areas

Q. Our family owns an unimproved lot at about 8500 feet in southern Utah. A combination of heavy snowfall, strong winds and disease resulted in blow down of dead and live trees. We are planning to clear the area to reduce the potential of fire and then seed native plants and wildflowers seeds. I cannot find any appropriate seed available to do this.

A. There are seed packets available locally and online labeled as wildflowers. But these are generic wildflowers and not all native to our area. You are right to be looking for seed appropriate to your area. Generic types of wildflower seeds should not be used for seeding near semi-primitive or primitive areas.

Introducing plants that are not native will result in future problems. Some non-native plants can invade undeveloped areas and “choke out” native plants. This results in multiple, successive future problems for other plants and animals relying on native plants.

Check out this document online from the Utah Native Plant Society regarding sources for native seeds. http://www.unps.org/index.html?PAGES/cohortlist.html. Also download the document from the University of Nevada titled “Living with Fire” which aims at reducing the fire potential for homes located. In the Lake Tahoe area of Northern Nevada but has information appropriate to your situation. https://www.unce.unr.edu/publications/files/nr/2006/SP0611.pdf

Talk with your local Forest Ranger and decide which of these seed choices would be appropriate for your location. If you have trouble downloading these documents, contact me and I can help you.

When you are ready to seed, seed right into the snow as it is disappearing in the spring. The water and warming soils will help the seeds to germinate.S

Does Newtown Pippin Apple Produce Good Flavor in the Desert?

Q. How has the Yellow Newtown Pippin apple performed in our climate. I would love to have one if the quality is good here.

A. I published a list of recommended fruit varieties for our climate and made available on my blog. These are fruit tree varieties I have evaluated over a minimum of five years of fruit production. It can be misleading to recommend a variety when it has produced for only one or two seasons. http://xtremehorticulture.blogspot.com/2011/10/recommended-fruit-trees-for-southern.html

I am not concerned so much whether this variety of apple tree will grow here or not. It will. My main concern is the quality of the fruit it produces in our climate and soils. Just because you like Macintosh apple you purchased from a local grocery store does not mean that a Macintosh apple grown here will taste the same. There are numerous potential problems with a Newtown apple grown in the desert. Only time will tell.

Yellow Newtown Pippin has not had a long enough performance history in our climate to recommend it for the general public. It ripens a little bit before Granny Smith and a month or so before Pink Lady and this is a good time for apples to ripen in our climate. However, other influences such as our soils and climate while it was growing will impact its quality.

Download a copy of my recommended fruit tree list

Extra reading about the Newtown Pippin and Yellow Newtown Pippin apples

https://www.slowfoodusa.org/ark-item/newtown-pippin-apple

http://www.orangepippin.com/apples/newtown-pippin

http://www.nytimes.com/2003/11/05/dining/it-s-crunch-time-for-the-venerable-pippin.html?pagewanted=all

Firewood and Pine Trees. A New Deadly Combination in Southern Nevada?

The following is a Release from the U.S. Forest Service and Nevada Division of Forestry regarding a new pest found in firewood in southern Nevada. This pest will leave the firewood and may attack pine trees in southern Nevada, in particular Mondale and Aleppo pines. From the sound of it, infested firewood was brought in from California into southern Nevada. If you think you have purchased some of this wood please contact the Nevada Division of Forestry for more information about what to do.

Goto Nevada Division of Forestry Contact Information in Las Vegas

Goto Mediterranean Pine Engraver Information from USFS

I was alerted by Jeff Knight from NDA that the Mediterranean pine engraver, Orthotomicus erosus (Wollaston), has been positively identified from two locations in southern Nevada. One site was near Blue Diamond and the other was a firewood distributor in Las Vegas.  The identification was confirmed by Jim LaBonte of the Oregon Dept. of Agriculture.  The beetles were trapped in Lindgren funnels with ethanol and alpha pinene as lures.  This represents the first record of this beetle in the U.S. outside of California.  The beetle appears to very aggressively attack stressed trees and rarely attack healthy trees.  The suspected host near Blue diamond is Pinus monophylla, no suspect in for the Las Vegas site yet.  Attached is the USFS Pest Alert for the beetle.  Further investigation of these sites will take place in early Jan. to determine possible hosts and entrance into Nevada. At this time NDA will not pursue any regulatory/quarantine actions, but will be working on educational information on the insect.

More information about the Mediterranean Pine engraver beetle

Freeze Protection Using White Breathable Fabric

Q. We use a white, breathable fabric for some of our tender desert plants when there's a chance of freezing temperatures.  We're at a 3000 foot elevation on the eastern slope of the Spring Mountain Range and temperatures can be 8° F more or less than those reported at McCarren International Airport. We go by the plant description temperatures and for 30 degree forecasts we cover those that could be damaged down to 20 F degrees. Can the fabric be left on continuously for long periods of time even though nighttime temps are higher than 32 degrees if it's anticipated that in a week or two or more temperatures will drop again below freezing?  Some folks who sell this product say it can be left on all winter but I thought I had better check with you.

Row crop cover used for cold protection for vegetable row crops 

A. Yes you can leave it on! This is a major advantage with these types of products specifically made for protecting plants from light freezes. They are called by several different names including crop covers, floating row covers, frost blankets and floating row crop covers.

Some background on these products will help you understand them. These covers are flexible, nearly transparent, extremely lightweight and made from fabrics that are typically spun or woven.

They “breathe” allowing light, rain and air movement through them but still capture heat coming from the ground. They transmit so much light that there shading effect on plants is only somewhere around 15 to 20%.

They gained fame primarily in commercial vegetable production about 30 years ago for two distinct reasons; protection of vegetables from light frosts and earlier production. When left on permanently during cool weather, they can raise air temperatures under the fabric about 5 to 6° F which causes vegetables to grow faster which in turn means they can be harvested earlier.

Besides protecting young tender plants from freezing temperatures and growing faster, they also provide another valuable advantage; insect protection. In organic production they are a valuable asset to leafy greens that can be damaged from wind, intense sunlight or chewing insects.

            Row crop covers are placed over new seedlings or transplants and kept from blowing away with metal staples and a soil covering the edges. They are also used as a covering for low tunnels used in vegetable production. 

Landscape Committee Wants Evergreen Shade Trees

Q. I am on our landscape committee for A Henderson HOA. We are going to remove many dead and diseases trees in our small community. Mostly privets that through the years have died after we converted to desert landscape from grass. Others are mainly ash trees that are diseased and or have dead limbs and with pruning look terrible. Most of our yards face either East or West. We have been advised to replace the trees with fruitless olives or living oak. All yards are small and have rock mulch. As many other communities we are cash poor and need to make a wise decision because it will be expensive. We are looking for evergreen, shade trees if possible.

I forwarded this question to Andrea Meckley, a Certified Horticulturist working in the Las Vegas area since 1992.

A.  I understand your situation with the privet trees doing poorly.  Since you are going through the expense of replacement I realize you want to make good choices.  Below are a few thoughts:

1. Fruitless Olives:

                  Pros:  evergreen, little leave drop 

                 Cons:  slow grower, sometimes they will fruit even though they are not supposed to.  If this happens you can apply a solution to stop them from fruiting if it concerns you

2.  Southern Live Oak: 

                 Pros:   evergreen

                 Cons:  slow grower, debris from leaves and acorns

Between the two above I would choose the Olive. 

 Young European olive

Young Live Oak

Since you have existing sycamore and desert willow trees that are deciduous, I would also consider the following medium size evergreen and semi-evergreen trees:  Xylosma tree (Xylosma congestum), Holly Oak (Quertcus ilex), Blue Palo Verde (Parkinsonia florida), Desert Museum Palo Verde (Parkinsonia 'Desert Museum'), Bay Laurel standard trunk tree (Laurus nobilis), and Shoestring Acacia (Acacia stenophylla) which may be a little messy. 

Palo Verde in Bloom

Young shoestring Acacia

One good source for good pictures and more information can be seen at Southern Nevada Water Authority website.  Please contact me if you wish to discuss further.

Andrea Meckley

Certified Horticulturist

American Society for Horticultural Science

imn2plants@aol.com

Leaf Drop Can Harbor Insects, Disease

Q. Is it best to remove all the leaves from the soil after they have fallen or leave them on the soil as mulch for fruit trees? My concern is about insects that might stay there during the winter and cause damage in the spring.

fr

From reader

A. In a very general sense I have two concerns regarding leaving undecomposed leaves at the base of plants. You are right, the first one is insect problems and it's very possible some insects will overwinter under loose leaves that have not decomposed.

            Remember to pick up any fruit lying on the ground as well. Do not leave dried fruit on fruit trees because of potential insect problems.

            One insect in particular is the grape leaf skeletonizer. Don’t leave debris around the base of grape plants because of this insect problem. Make sure leaves are shredded or composted. If you have one, lawnmowers are efficient leaf shredders.

The second potential problem is disease. There are a few diseases that cut overwinter on fallen leaves. It is always better to compost or shred leaves if you're going to leave them around the base of plants. Sanitation in the garden is important.

Fungus Gnats Problem in Potting Soils

Q. It seems no matter what brand of potting soil, I have to bake it before I can use it. If I don't, I get hundreds of tiny flies that hatch and swarm. I put out water to catch and drown them. I spray insect oil on top of the soil several times a day. I'm so afraid I'll kill the plants.

A. Yes, fungus gnats in particular are a big problem in potting soils used for houseplants. The younger generations feed off of both decaying plants and soft, succulent living roots. They aren’t very particular about what they feed on, living or dead, so long as it is soft, juicy and tender.

If fungus gnats are extremely happy in their environment they will multiply very rapidly and cause poor growth and stunting. Besides, they are pesky and a nuisance inside the house. If potting soil is sterilized by the manufacturer using a heat treatment it should kill all of the fungus gnats and should pose no problem.

Control fungus gnats with organic pest control products such as beneficial nematodes that go after their destructive larvae and a bacterium is also available with a similar result. You should be able to find these products in your local nursery or garden center.

Yellow or blue sticky traps also work. I received this video on how to make yellow sticky traps from a friend.

Another effective method is to sterilize this potting soil yourself by placing it, moistened, into a clear plastic bag and let it bake in the sun. Temperatures need to get up to about 160 F for at least 30 minutes for good control.

Another option is to apply pyrethrin sprays to the soil and water it in.

More information about fungus gnats from the University of California

Am I Applying Too Much Nitrogen?

Q. We fertilize all of our bushes early spring and mid fall with a 5-10-5 liquid plant tonic.  Hopefully this isn't too much nitrogen.

This concentrated fertilizer
 has no nitrogen but very
high percentages of phosphorus
and potassium

A. There are two ways to look at this question. Applying too much nitrogen can mean either applying it too often or applying too much in a single application. If you follow label directions, the amount of nitrogen applied should be correct. Apply nitrogen as often as 8 weeks apart if you want continuous growth.

             Applying excessive amounts of nitrogen can damage plants or cause excessive growth of leaves and stems.

            When judging how much fertilizer to apply and how often, observe the plant. If the plant does not have good growth or the flower size and numbers have diminished, apply fertilizers or “plant tonics” if you prefer.

Applying too much nitrogen, the first number, is not normally a long-term problem. The potential long-term problem involves the over application of the second or middle number, phosphorus. 

Phosphorus stays bound in many soils for much longer periods of time than nitrogen. Apply fertilizers containing high levels of phosphorus (middle number) less often than fertilizers that contain high levels of nitrogen.

As a general rule of thumb, apply fertilizers containing phosphorus once a year to established plants, two weeks before flowering. The rest of the time use high nitrogen fertilizers.

The exception is at planting time. Every time seed or transplants go in the ground, apply a high phosphorus fertilizer. Before planting, mix high phosphorus fertilizers in the soil to the same depth the roots will grow.

Bagged compost can be hard to find. Most
bagged products that contain compost are
soil mixes, not straight compost.

Consider using compost instead of a mineral fertilizer. I am talking about compost which is harder to find, not a soil mix that contains compost. Most composts have a good balance of nitrogen, phosphorus and potassium and can be used as a substitute for mineral fertilizers.

Composts provide plants with a lot of minor elements not found in mineral fertilizers. Compost lowers soil alkalinity, stimulates good soil microorganisms and provides humus or “black gold” to the soil. It is a very powerful addition to desert soils.

Some Houseplants Need Their Roots Pruned

Q. We repotted a house plant that was constantly wilting and that seems to help. Is it possible that the plant is too large and needs a “haircut”?

A. Potted plants benefit from root pruning as well as top pruning if it is possible to do so. I guess we could call this a “haircut”. Both the top of the plant and its roots should be “in balance” with each other. We sometimes refer to this as a plant’s “root to shoot ratio”.

            More about root to shoot ratios

Not all plants can be root pruned and top pruned to make them smaller so they perform better in their container. Some plants will need a larger container. Some plants are made smaller by “dividing” the plants. Plants that require division are removed from their container and separating a “clump” of plants into individual plants with a sharp, sanitized knife or pruning saw. The cut ends are dipped into a fungicide before replanting.

Some plants require renewal through propagation. Typically these plants are propagated using methods such as stem cuttings, leaf cuttings, root cuttings or layering. These specialized propagation techniques are specific to certain plants. The Internet is a good source of information on propagating interior or houseplants.

Propagation of Houseplants

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Pruning Roots of Plants Gives Added Control

Did you know that the roots of plants can be pruned? This is called root pruning and dramatically alters the root to shoot ratio of plants.

Root pruning, what is it?
As the name suggests, root pruning is the cutting of roots. It is done for different reasons than pruning the tops of plants. We have total access to the tops of plants. Axis to the roots of plants is much more limited. Roots grow differently from stems. Roots do not have buds. You can virtually cut anywhere on a root and it will "sucker" unlike many of the stems of trees and shrubs.

Why root prune?
The most common reasons for root pruning include controlling the size of the plant, slowing the growth of plants, initiate flowering, keep the roots closer to the trunk, keep the roots out of problem areas or creating problems.

This is a root pruning machine used in nursery practices for undercutting trees growing in the field under production.This machine is driven so that the young trees are undamaged as they pass under and between the tracks. The U-shaped blade is pulled behind this machine and undercuts the roots...root pruning... to make a bare root fruit tree that will transplant to the field with fewer losses. Photo taken by me at Dave Wilson Nursery www.davewilson.com 

Root pruning is commonly done in the nursery operations where trees and shrubs are grown to be transported for planting in a new location. Root pruning is common in bonsai to reduce the growth of plants and keep them small. Root pruning is done in some greenhouse operations for similar reasons to nursery operations.

If root pruning is not done and the top of the plant dies or is severely pruned back, then the top regrows again very quickly to its original size. Once it reaches this size, growth slows again. This is the plants way of reestablishing what we have called the root to shoot ratio of the plant. The plant "recognizes" the difference in size between the top growth and undisturbed root size. The plant directs its growth, the flow of carbohydrates and hormones, to the top of the plant at the expense of growth in the roots.

How can I use Root to shoot ratios?
If a plant is growing too rapidly and you want to slow it down, root prune it. Take a sharp shovel and sever the roots by pushing it through the soil and through the roots as deep as possible.

Do you want to keep the roots of plants from entering the septic tank or other problem areas? Root prune between the plant and the problem area. Root prune every 2 to 3 years.

Some diseases are transmitted from plant to plant when the roots fused together and what are called "root grafts". This commonly occurred in American elm with the transmission of Dutch elm disease. Root pruning can isolate plants from trees that are carrying the disease. If an Apple or Pear tree dies from fire blight, root prune the area around the dead tree to prevent the transmission of the disease through root grafts.

When Retrofitting trees and shrubs from a lawn area to drip irrigation, consider root pruning these trees and shrubs to generate roots closer to the trunk were the emitters are placed.

Having trouble with the tree flowering? Try root pruning to create a new root to shoot ratio that might slow the top growth and induce flowering.

How Many Days between Waterings in the Winter?

Q. I am not sure how long some of my trees can go without water during the winter. I have a mature Pepper, Mesquite and some palms that I have not watered for 10 days because of the cold temperatures. Is 10 days between watering okay?

A. 10 days between waterings should be no problem for trees and large shrubs provided they were given a deep watering prior to this. Deep rooted plants, like most trees and large shrubs, can go without water for a longer period of time than smaller plants. Deep watering means flooding the soil with water to a depth of 2 to 3 feet. If drip is used then making sure enough volume of water is applied to soak to a depth of 2 to 3 feet.

Applying water with drip emitters this close to the trunk is okay for the first couple of years. As this tree gets larger, more emitters will be placed underneath the canopy of this tree and further from the trunk. About half the area under the canopy should receive water. Apply enough water in a single application to wet the soil to a depth of 2 to 3 feet.

Many landscapes have small plants and big plants on the same circuit or valve. This means the small plants cannot be watered separately from the larger plants. The small plants require water more often. This forces the larger plants to be watered frequently even when they don’t require it. 

This twisted Acacia would be considered a desert tree. Putting a tree like this on an irrigation circuitFor desert plants gives greater flexibility when applying water. Applying water more often causes it to grow faster, larger and more dense. Applying water less often keeps it smaller, growing more slowly with fewer leaves.

Secondly, plants that do not originally grow in desert climates must be watered more often than plants which do. The mesquite and California pepper are both desert-type trees where water can be withheld for long periods of time with no problems. Palms are more shallow rooted and require water more often. But ten days is not too long for any of these plants during the winter.

In an ideal world the deeper rooted plants would be on a separate irrigation circuit or valve from shallow rooted plants. Deep rooted desert plants like acacia, palo verde and mesquite would be on a separate circuit from the other non desert deep rooted trees and shrubs. This gives you alot of flexibility in watering. 

Palo Verde is another desert tree whose growth can be managed by applying more or less water. Putting desert trees and shrubs on their own separate irrigation circuit gives you this type of flexibility.

The deep rooted plants would include trees and shrubs and deep-rooted woody perennials that die back each year such as Bougainvillea. The shallow rooted plants would include annuals and flowering perennials that die back each year like Lantana. Lawns should be on a separate circuit but could be tied into vegetables as long as the water could be turned off to vegetables between seasonal plantings. 

When to Harvest Oranges?

Q. My oranges are turning orange. How long should I wait before I harvest them.

Yes, oranges and other tender citrus will grow in Las Vegas but not without some careful considerations.

A. Oranges do not necessarily turn orange before they are ready. Orange color develops due to climate. In the tropics oranges remain green or green/yellow even when  they are ready to eat.

Fully ripe oranges in the Philippines. They do not turn orange because of the warm climate. The fruit above it is rambutan.

Orange color is induced in oranges that don’t develop good color using ethylene gas in closed rooms where orange color is important for marketing and sales. The best way is to pick one and try it. If sufficiently sweet, harvest the others or wait and harvest when needed during cold months but leaving them on the tree too long can reduce the number of flowers in the next cycle of fruit production. When they are ripe start removing them. Cut the stem close to the fruit, don't pull the fruit from the tree, for better storage life.

Handheld refractometer used for measuring total dissolved solids (sugar content) from the juice of fruits and vegetables.

A sophisticated method is to purchase a small handheld device called a refractometer and measure the sugar content. Maturity in fruit is usually a measure of the sugar content which the refractometer will read for you.

How Often to Water Fruit Trees in the Winter?

Q. Do you have any guidelines for watering fruit trees in the winter?  I cant find anything specific to winter watering on your web page. I have apricot, nectarine, apple, fig, pear, plum, cherry, peach, orange - planted spring 2015.  I am not expecting the apple or cherry to make any fruit yet, They are just ornamental. Pomegranite, jujube, lime, grapefruit I planted 3 years ago. Will deep watering once a month suffice for December - February?

Fruit tree with irrigation basin surrounding the trunk. Irrigation bubbler at the top right of the basin that allows 2 gallons of water to flow from it every minute. The basin must be level so that water flows evenly across its surface.Surrounding the trunk is rabbit protection.

A. Once a month is not even often enough for trees established for years in our warm winter desert climate. Once they have been established, trees established for one season might be closer to every two weeks during the winter. If the soil is very sandy, then once a week. Fruit trees surrounded by dry soils should be watered more often than trees in wet soils. Wet soils in the desert might happen if fruit trees are grown close to a lawn area, a wall that has irrigation applied on the other side of it, intercropped between the trees with other plants like vegetables or herbs.

Irrigation basins surrounding newly planted fruit trees that have been staked and mulched with wood chips. The screening around the trees is for rabbit protection which also keeps the wood mulch away from the trunk. If drip emitters were used, two emitters might be enough for the first 2 to 3 years. When they have reached 2 to 3 years old than increase the number of emitters to at least four.

Generally speaking, if there is a surface mulch of at least three inches, add one to two days in the summer and up to one week in the winter. Sandy soils require more frequent watering with smaller amounts applied. Desert soils should contain 50% compost at the time of planting. Fruit trees perform much better with wood mulches applied to the surface and require less frequent watering.

General Watering Schedule for Fruit Trees
Let me run down a general schedule of watering fruit trees that is ignoring rainfall since we only receive an average of 4 inches (10cm) or rain each year.

Newly planted in spring or fall during cool weather....2-3 days; winter 1 to 2 weeks depending on soil and mulch covering. After growing for one season then assume the trees are established.

Fruit trees established at least one season with fruit or nuts on the tree... Summer every three to four days depending on soil and mulch. Spring and fall, weekly. Winter every two weeks. Fruit trees that have been harvested can be watered less often.

How Should I Care for My Fairy Duster Plant?

Q. I'd appreciate some pointers on how to arce for fairy duster plant So it becomes healthier and a better looking shrub. Very little has been done because the bees are usually on it.

Fairy duster and honeybees

A. This plant is native to North and Central America growing in warm desert climates and soils. This tells you a little bit about how to manage it. This should tell you to not water every day. Plants like this are usually very susceptible to root rot so make sure the soil has been amended with compost before planting so that it improves drainage.

Fairy duster in the backyard of reader

It will tolerate desert soils as well as infrequent watering. At planting time I would amend the soil with about 25 to 50% compost and make the whole about three times wider than its container. I realize yours is already in the ground so watering and fertilizer applications are important to mention.

Do not water this plant too often. That will be the biggest mistake people make. Fertilize it lightly once in the very early spring around late January or February with a rose type fertilizer. The plant can get 3 feet wide and 3 feet tall in soils that have been amended with compost.

As long as it's in a sunny location you should see a profusion of blooms in the spring and summer months that attract bees, hummingbirds and night flying moths. Quail like to feed on seed from the seed pods. Rabbits like to browse on new growth.

You can clean up the plant in the early spring by removing dead leaves and stems. You will encourage more blooms if the plant is in a sunny location and flowers are removed before they begin to form seedpods.

Every Potting Soil Contains Fungus Gnats

Q. It seems no matter what brand, no matter where I buy my potting soil I have to bake it before I can use it.  If I don't, I get hundreds of tiny fly that hatch and swarm.  I put out water to catch and drown them. I spray insect oil on top of the soil several times a day. I'm so afraid I'll kill the plants.

A. Yes, fungus gnats are a big problem in potting soils and they can create damage to plant roots. They feed off of both decaying plant parts and soft, succulent living roots as well. Potting soil does not smell very good if you have to put it in your oven at 150° for 15 minutes to kill these nuisance critters.

The larvae can cause damage to new, tender roots of plants. If they are extremely happy in their environment they can multiply very rapidly and cause some severe damage. Besides that, they are pesky and a nuisance inside the house.

This is Garden Gourmet potting soil and I have never seen fungus gnats in this product. However, bagged potting soil that is not been heat treated will carry fungus gnats. This product sells for $5 for one cubic foot.

If potting soil is sterilized with a heat treatment by the manufacturer it should kill all of the fungus gnats. If the soil is introduced into an environment where there are fungus gnats present then it will get reinfested again.

Here is what the University of California says about them

They can be controlled with some organic pest control products; nematodes that go after these larvae and a bacterium which does the same thing. You should be able to find some of these products in your local nursery or garden center. I have never used them so I am reporting only what has been reported on the internet using these methods for fungus gnat control. However, cooking them does work.

Where to get beneficial nematodes
Where to get beneficial bacteria  It says for mosquito control but it is the same product used for fungus gnats and will be included on the label.

Another method is to sterilize this potting soil yourself by placing it moistened into a clear plastic bag in full sunlight and let it bake. Temperatures need to get up to about 160 F for at least 30 minutes for good control. Keep in mind that if you introduce this back in the environment where a fungus gnats are present and they will reinfest this sterilized potting soil. Another option is to apply pyrethrin to the soil and water it in.

When and How to Prune Lantana and Oleander?

Q. How and when should we prune our lantana and oleanders?

This is a Lantana I saw pruned by a local company. Leaving this much wood remaining will make it very "twiggy" at the base. You can actually prune it much closer to the ground in this.

You can see from this close-up that I took last February that suckering can occur much lower on the stems of Lantana. Don't be afraid to cut it close to the ground. Leave about 1 inch for suckering.

A. Both of these plants are pruned during the winter months since they both produce flowers on new growth during the summer months.

After pruning, apply a high nitrogen and high phosphorus fertilizer to push new leaf and stem growth and dark green color. The phosphorus will help to promote flowering. Flowering will not occur until the top growth is large enough and comes into balance with the existing root size. This is sometimes referred to as the root to shoot ratio.

 I would delay pruning them until late winter (late January) unless you don’t mind looking at "dead" space (the space is not occupied by anything). For lantana it normally freezes during winter months and you have a choice whether to leave the dead top of the plant in place or cut it down to the ground, leaving one inch of stems remaining to support the new growth beginning in February.

You can prune oleander close to the ground, just like Lantana. Cut it back to within 2 to 3 inches of the soil surface. This is the time of year to do it up until about the end of January when it begins to push new growth all by itself.

            Because the roots are fully grown, alive and healthy you will see very rapid growth in the spring. Fertilize the pruned plant in late January or early February to encourage new growth and flowers. Use a fertilizer that supports flowering plants such as a rose fertilizer blend or other fertilizer for flowering plants.

You can see from this picture that new growth is beginning to sucker from the base just like Lantana. Apply a fertilizer near the base of the plant close to a source of water. Use the same fertilizer as the Lantana. A rose type fertilizer is fine.

Oleander will regrow very quickly when cut back close to the ground, fertilized and watered. This was one month after pruning. Nitrogen in the fertilizer will push leaf and stem growth along with dark green color. Phosphorus in the fertilizer will push flower growth and flower size.

            Oleander is pruned at the same time of year as lantana because it also blooms on new growth, not older growth. You can chose to remove 1/3 of the plant by cutting these largest stems to the ground for renewed growth at the base or you can cut the entire plant to the ground and let it regrow. Your choice. Either way you will see luxurious growth and lots of flowers next year. Again use a fertilizer that supports flower growth and apply it early in the spring.

This is an example of a fertilizer that will push leaf and stem growth and dark green color. You would apply this immediately after pruning and water it in. A 10 pound bag sells locally for $7.95

This is an example of a fertilizer that it increases the number of flowers and their size. It should be applied about 4 to 6 weeks later. A 10 pound bag also sells for $7.95 .