Is ball moss killing my live oaks in Austin?

I get this question very often.  People see the ball moss in the live oaks on the dead limbs and automatically think it is killing the branches and that it will eventually kill the tree if it is not removed.   The truth is that ball moss is an epiphyte, or air feeder, and is not parasitic to the tree.   Because it is growing inside the canopy in shady areas around here, it looks as though it is killing tree limbs, when in fact the limbs are dying naturally over time due to lack of sunlight penetration.  Unfortunately, many less reputable and/or uneducated sales representatives for some local tree care companies often use the interior limb death as a fear factor and a sales tool to sell extensive ball moss removal for their companies.

However, the truth about ball moss with respect to tree health is not always completely cut and dry.  I attended a seminar on ball moss about five years ago at Texas A&M by Dr. Todd Watson who is Urban Forest researcher at Texas Agricultural Experiment Station and an expert on mistletoe and ball moss (as well as a great guy).  When the class full of professional, certified arborists were asked if ball moss is detrimental to plant health, half of the class raised their hands and the other half did not (I did not).  This was very interesting.  The reason for the split had to do with where specifically in Texas the arborists were practicing.

In humid areas of Texas, especially around lakes and bodies of water, ball moss infestations can be huge.  In the Austin area, however, the air is dryer and even by water, the infestations are generally not as bad.   In humid areas where ball moss is severe, it can actually grow over the ends of limbs in the full sun, causing the branches to actually be shaded out at the tips and killing sections of the outer canopy.  In these instances, it needs to be pruned off or sprayed.

Here in Central Texas, the way I handle ball moss on live oaks is to prune it out of the trees.  The air is generally quite dry here, and the infestations are rarely severe.   Trees with larger amounts of dead wood that have formed since the last pruning cycle are more apt to have ball moss.  As the canopies thicken back up since the last pruning cycle, the interior limbs die due to lower of sunlight penetration, and more ball moss forms on these limbs, and often on the interior living limbs as well, although generally not to the same extent.

It is important for long-term tree health to remove dead limbs from the interior of oak trees over time, especially large dead limbs.  This then allows the trees to heal over and compartmentalize rot, helping to keep the living limbs healthy.   As the dead wood is removed, so goes the ball moss.   Since the trees generally do not form that much ball moss between pruning cycles, it is not an issue in most cases.   Since spraying is costly, does not address the pruning needs of the tree, and is generally not necessary due to mild infestations, you will rarely see ball moss spraying as a preventive measure around here.

Is oak wilt treatable and how?

Once oak wilt is diagnosed, many people are at a loss as to what to do.  In the course of my career here in Central Texas, upon being called onto a property, many people have told me that once live oaks get oak wilt, that they are untreatable and that they should just let them die.  This is simply not true.

The most important factor to diagnosing oak wilt is diagnosing it early. If you in any way think that your oaks may be in decline, immediately call me out to inspect them. At this point, I will be able to either eliminate the possibility altogether or, immediately diagnose the disease and start treatment right away.

The longer you wait, the more damage the fungus will do to the tree, and then a successful treatment is less likely. In some cases, even a 20 percent defoliation can be evidence that the disease has progressed too far, and a treatment will be unsuccessful. Generally speaking, when an infected oak is treated, if it takes in enough material, it tends to stay at the canopy density it has when it is treated. This is why you often see live oaks that have been treated looking so thin and defoliated.

We use Alamo fungicide, generally at 20 milliliters per liter, and generally only treat trees once they have been diagnosed with oak wilt, or are in a stand of oaks that are symptomatic.   Trees put on new rings of growth every year, creating thicker trunks, roots and branches, and new roots and shoots.  Since this is new living tissue, once the Alamo has been injected into the tree the new years subsequent growth does not contain the chemical, and is not protected. We used to recommend treatment initially as a preventive for five-year intervals, with re-application every five years thereafter. Now, we are recommending treatment every two years; but only when the trees are either symptomatic or at high risk of contracting the disease within 12 months after treatment.  We use the recommended Texas A&M macro-injection method.

On larger properties such as parks and ranches, or in certain neighborhoods, sometimes trenching can be a good idea.  When hundreds or even thousands of oaks are at risk from oak wilt infected trees on property perimeters, often root severing through trenching two feet deep is the best and most cost-effective option for keeping out the disease. This is NOT a panacea, and it will NOT keep beetles from spreading the disease to healthy trees under ideal conditions, but it CAN keep the disease out in certain instances. It is better undertaken where large natural areas and large amounts of trees make Alamo treatment economically unfeasible. In neighborhoods, streets and sewer lines are essentially trenches, and the disease is often confined to city blocks once new beetle infections occur.

Cabling and bracing trees

Central Texas Tree Care has installed hundreds of cables in Austin area trees over the last 10 years and I am very proud of our record. My staff is highly trained and seasoned in this area and we now properly install more cables every year than just about any other local company. The purpose of this article is not to be overly technical, but rather to explain to the average person that we know exactly what we are doing, what standards to follow and what hardware to use.

Cabling and bracing trees are scientifically approved methods for supporting trees with split crotches, or for trees that have limbs or crotches that are predisposed to failure. The International Society of Arboriculture, ISA standards for tree cabling that we follow are called the ANSI (American National Standards Institute, Inc.) A300 standards for supplemental support systems. When done properly, cabling and bracing will often save limbs or entire trees. They are generally considered permanent solutions, although constant re-inspection and monitoring/pruning is always recommended.

Cabling trees is generally done to tie in either limbs that are overextended (too long and heavy), or to tie in large limbs in the upper canopy to support weak or split main crotches. Cables are almost always installed in conjunction with canopy thinning to reduce the end weight of large horizontal sections.  Sometimes, come-alongs are also used to help pull together split crotches so the cables can be properly tied  in. Often with split trees, (although not always necessary) threaded through-bolts are installed through the split crotch for added support.

Through-bolts are used as anchors. These are galvanized metal bolts, with a fully enclosed ‘welded’ eye and are installed right through the limb to be supported. A hole is drilled through the limbs at exactly the right angle and then the bolt is slid through the limb. After the bolt is in place, a washer and a nut is then put into place on the back side of the limb. This practice makes for a very solid and permanent anchor solution that will not pull out of the tree or rust. Nor will it interfere with the natural expansion of the limb. Additionally, the ring on the inside will not break. With cheaper hardware, often the ring is not a welded eye and the cable pulls out during the first storm.

Once the anchor bolts have been installed, then the cables are tied to the anchor bolts using thimbles.  The two strongest ways to do this are either with ‘dead-end grips’ or twisty ties as we call them, or by bending and splicing the cable itself through and around the eye ring, then splicing it. Both of these methods are extremely strong and effective.

Most (not all) cables I see installed by other companies in the Austin area are installed incorrectly.  Almost every time, besides using inferior hardware, the cables are installed either too low in the tree or too far down the limb they are supposed to support. ANSI A300 standards specifically state that cables should be installed a minimum of two-thirds of the way from the crotch to the end of the limb being anchored.

The cables and bolts need to be the right size for the job. Large trees and limbs require larger bolts and larger diameter cables. Smaller trees require smaller diameter bolts and cables. Limbs that are being used to anchor the tree require large enough diameters to support the bolts, but conversely putting bolts that are too long into large diameter wood is often not correct either (too far down the limb).

Safety factors such as proximity to power lines or other utility lines are paramount. Metal cables conduct electricity and must never be installed in trees where power lines contact the tree. Also, metal cables can rub against themselves or tree limbs, so they must always be installed free from obstructions.

Trees with multiple large limbs and weak crotches often require multiple cables. Often triangle, box or ‘wheel and spoke’ systems have to be installed.  When more than one cable has to be anchored to the same limb, more than one anchor bolt must be installed (one for each cable). The anchor bolts must NOTbe closer together than the diameter of the limb being drilled. Note: For safety and power, we use gas powered drills with forward and reverse settings, instead of electric drills that require a dangerous power cord.

Although lag bolts are on the approved list of hardware for ANSI A300 cable systems, we prefer to stick to through-bolts. As an arborist with more than 15 years experience installing support systems, I find lag bolts to be unpredictable and weak anchors, especially in large trees. They often pop out in storms.  Although they work better, for example, in oak limbs that have stronger wood, and are significantly easier to install, I have seen them come out or generally fail too many times in stormy weather. I would NEVER recommend lag bolts in softer wooded trees other than oaks, mesquite or black walnut trees in this area and prefer not to use them at all.

Often cables are not necessary at all, and I have seen cables installed when they are not needed with startling regularity. Always get your trees evaluated first to see if they even need cabling or bracing. I often see other tree companies promoting them because the crews need the work and not because the tree in question actually needs a cable. Beware of unnecessary tree work! Contact us if you want an honest professional evaluation.

Fake grass under your trees?

Fake grass. When we think about fake grass, many of us think back to the astroturf in football stadiums, or the cheap fake grass they used to use in the grocery store produce sections or various department stores. The fact is that ‘fake’ or man-made grass has come a long way since then. Stick with me here.

Now, you can actually buy artificial grasses that look like fescues, buffalo grass, St. Augustine or Bermuda as well as many other species. Not only that, but there are actually companies out there that help you pick out what you like and actually install it for you! Install it, you ask?

A football field for a yard?

The first time I saw an artificial lawn in the Austin area I couldn’t believe it. I could not understand the appeal at the time, but had not really even thought about it before. Upon further reflection and after living through this record-setting drought, it’s all started making sense. The watering, the weeding, the chinch bug applications, the fungicide applications, the mowing, the edging, the fertilization, the yearly dillo dirt application, the watering, the watering, the watering…

It’s no wonder people are looking for other options. Standard xeriscaping is not for everyone. The goal here is water conservation and the reduction in fertilizer and chemical applications.  But, how can it be good for trees?  I thought it would be awful for trees, suffocating and sterilizing the tree roots. Boy, was I wrong!

Better than the real thing?

Artificial lawns are porous, allowing water and oxygen to get to the tree’s absorbing roots. Artificial grass has no roots to compete with tree roots. Weed killers, which are always used on lawns and which often kill trees outright via Roundup, weed and feed or other herbicides, are no longer needed. Pollution due to lawn mowers is eliminated.  Thousands or dollars per year are saved by the homeowner. So let me get this straight, the trees are actually happier and the homeowner saves money?  Exactly!

I never thought I would be touting artificial anything. I hate artificial Christmas trees, wreaths, etc.  In this case though, there are more than a few things to think about.  First, we live in a desert environment here in the Austin area, where everything has to be artificially watered in order to survive in the blistering dry summer heat. Droughts are constant. Water is expensive, and as you water the grass it grows and then has to be mowed and maintained.  Water is a limited resource and we all waste more of it than we should.   If not for irrigation, it would all be live oaks, cedars and cactus in the yard.

Think about this.  We treat water so that it is potable (drinkable), then waste it on our lawns. Lawns don’t need heavily treated, drinkable water!  Jerry Jeff (the country artist) told me recently that he has a house in Belize where he has a holding tank under the house the same size as the foundation. This tank catches the rain water that is then used to flush the toilets and irrigate the landscape. What is the point in heavily treating water that you flush down the toilet or use for irrigation? Not only that, but the chlorine used to treat water is not optimum for plant health anyway.  This is simply one thing most Americans just don’t think about.

An idea worth considering

So back to fake grass.   It’s just another option for the Austin area.   Maybe it’s not for you, but maybe it is.  It is expensive to install, but once installed it looks real!   And it lasts, too.  For up to 10 years or more before it starts to fade.  We are getting better at making it, and it’s a more viable option than ever before.  As we seem to be getting worse and worse droughts here all the time, andLakeTravisjust gets lower and lower, maybe we should be getting more creative with our options.  I’m just saying…

Improper pruning and its effects

Topping? Lion-tailing?  What do these terms mean? 

Of the damage that can be done by improper pruning, topping and lion-tailing are certainly two of the worst things that can be done to tree.

Why you shouldn’t top your trees

Topping involves removing the tops of the limbs and leaving huge, ‘stubbed off’ limbs and nothing else. A fellow arborist I worked with over 15 years ago likened it to a person having their arms and legs cut off.  More often than not, it kills a tree outright.  If the tree does survive, it has to tap into all of its energy reserves to re-grow multiple limbs from each cut. Unfortunately, as these new long skinny limbs re-grow around the outside of each large wound, the center of the wound then begins to rot slowly over time.  While the weakly attached re-growth often eventually breaks at the area of attachment, the actual limb itself rots from the center causing even weaker and more dangerous limbs over time.

Topping typically kills slow growing trees, such as oaks, right away. Unfortunately, these are the trees that are the best at compartmentalizing rot and have the strongest wood.   Also, topping usually kills excurrent trees such as pines or bald cypress (that have a pyramidal shape and one dominant, central leader), outright.  Survivability after topping is much higher in faster growing, softer wooded trees such as maples or ash trees.  Unfortunately, these are the very trees that rot the fastest because they are poor at compartmentalizing rot.  These softer wooded trees quickly become hazardous after topping.

Heading is like topping, but is done to an individual branch.  Heading back a limb has the same effect as topping.  If the limb gets enough sunlight, it re-sprouts many new branches from the cut.  These branches are also weakly attached, and unsightly.  Branches that are pruned properly are much less likely to re-sprout.  If limbs that are in full sun are headed back into the canopy and are shaded, they typically die.

Why lion-tailing should never be done

Lion-tailing, or ‘poodle-tailing’ is done by stripping branches of all their lateral limbs, except for the branches at the end of the limb. This causes the limbs to look like a lion’s tail, or a Dr. Seuss truffula tree, for example.  This is extremely bad for the tree, and causes the limbs to eventually break off due to the excessive weight at the very end of the branch. This also has a weakening effect over time.  Limbs have many living ‘lateral’ limbs along their length.  These lateral limbs have the effect of strengthening the limb over time as they expand, but also have the effect of increasing the limb diameter at that point along the limb, increasing taper by increasing the limbs diameter at that point along the branch.   Limbs with little to no taper are always very weak, and much more prone to failure.  Add to that the effect of weighting the branches only at the ends, and we have a seriously unsafe situation that gets much worse over time.

Certain trees, such as maples, are more prone to re-sprouting.  Oaks, for example, often do not re-sprout.  Certain trees have more inner leaves than others.  Oaks, for example have much less interior leaf growth than maples, ash or elms.   This contributes to the trees ability to re-grow leaves in the center after limb loss.  This is of course taken into consideration when pruning each species.

The costs of improper pruning

When it comes to pruning, you can pay a great deal of money to have your trees destroyed.  I have seen it happen before many times.  Years ago my neighbor paid $2400.00 to have his four ash trees lion-tailed.  For five years after he had it done, limbs were continuously breaking and hanging down in the canopy, causing hazardous situations continually.  Over-thinning or topping trees leave you with an additional expense to have them removed when they die.  Then you have the expense of re-planting as well.

I still see these types of poor pruning today.  Although it is not as prevalent as it was years ago, it does still happen.  Bad pruning cuts are a daily occurrence with poorly trained pruning crews. A ‘flush cut’ that cuts off the branch collar cannot be corrected, and may never heal, leading to rot and even tree failure in the future.  Stub cuts, although they can be corrected, are unsightly and can also lead to decay and infection when left.

It is better to get a seasoned certified arborist out to your property to have it done properly the first time Trees can add up to 20 percent to your property value.  There is simply no substitute to hiring the right person when it comes to your valuable trees.  Don’t cut corners.  Often you will even pay the same for bad pruning work, as you would for a quality job.  Call us for a free estimate!

About dead limbs in live oaks

Are there smaller diameter dead limbs throughout the canopy of your live oak?

In a drought, the live oaks, as with most trees are also experiencing stress.   The good news is that live oaks are extremely drought tolerant.  They are resilient and can handle long periods with very little water.  Very few diseases affect live oaks, and those that do (oak wit aside) are often not fatal.

It is important to note that live oaks form dead wood in the inner canopy naturally over time.  This ‘interior’ dead wood is normal and forms because the interior limbs get less sunlight as the outer canopy grows and thickens over time, causing them to drop their leaves and ‘shed’ these branches.  The scientific name for this branch shedding is cladoptosis.

Occasionally, live oaks lose previously healthy limbs in the canopy.  These can be caused by physical damage such as wind damage or vehicle damage, or in rare occasions they can be disease related.

When trees are weak from stress, they are more susceptible to disease.  One of the diseases that live oaks get more frequently during drought years is a fungus called twig blight, Cryptocline cinerescens.   It is not widespread in theAustin area, but when it does happen, it can be scary to the homeowner.   Since most local arborists are not familiar with this disease, it is often misdiagnosed.

I was first introduced to this disease 20 years ago inNorthern California, where it is much more prevalent.   The disease is characterized by many dead and dying limbs of smaller diameter, scattered throughout the live oak canopy, usually but not always fairly evenly distributed.

This disease is rarely fatal.  Most of the time, it is just responsible for the death of specific smaller limbs throughout the canopy which then can be pruned out past the transition zone into the healthy wood.  After that, we usually spray the tree with a fungicide to address re-infestation.  As with all diseases, initial and correct diagnosis is the key.

Why do Bradford pears split?

Maintaining Bradford pears in the United States is a multi-million dollar per year industry. When Bradfords were more widely planted, billions or dollars were spent maintaining, bolting, cabling and bracing them. Cities are and have been moving away from Bradford pears for years, and are replacing them with less problematic, more easily maintained and longer lived species.

Every time we have a storm of any intensity, I ALWAYS get a phone call for a split Bradford pear. Upon inspection, the question always arises as to whether or not to remove the broken limb(s) or, in cases with extreme tree/trunk damage, remove the whole tree. Often the damage it too severe or the aesthetics of the tree is so compromised the homeowner wants to remove and replace.

Another problem with Bradford pears is that they do not live very long. A life expectancy in the range of 18-25 years is typical, depending on the site. As for the size, people are often surprised at their canopy spread as the trees approach maturity. When they start getting large, the limbs have a tendency to have very few upright limbs, as most of the limbs pull down as they thicken up. This leaves the center sparse and aesthetically displeasing to many people.

The reason Bradford pears split, is quite simple. Firstly, they have numerous limbs that all originate from the same point on the stem. These limbs all have weak, acutely angled crotches to begin with, all with included bark. Included bark is bark that forms on the inside of the branch unions, and where it forms there is no wood to wood connection. Additionally, as these limbs expand in diameter they put pressure against one another. As these limbs are already weakly connected due to the included bark, the additional end weight exacerbates failure potential. Add to this weak dry wood, due to drought conditions, or wind and added water weight in summer storms, and you have a recipe for disaster.

I have had customers in tears before due to Bradford pear failures from summer storms. If it’s the only front yard tree you have, it can be quite devastating to the landscape when it fails. They are beautiful trees in the springtime. They explode with striking white flowers, and they are relatively bullet-proof with respect to most diseases. Also, there is no messy fruit to deal with.

So, are there any substitutes for Bradford pears? Yes! There is the aristocrat pear, Pyrus calleryana, ‘Aristocrat’, 25-45 feet tall at maturity and considered a much better species, with a dominant trunk and more open form. Why reputable tree nurseries still sell Bradford pears is beyond me. There are of course many other species to consider as well, such as crepe myrtles, non-flowering species like Chinese pistache trees, and many others.

If you do have a Bradford pear, it is not necessarily the end of the world. If the tree is maintained and thinned out regularly, and cabled in extreme cases, it can give the homeowner many years of shade and spring color.

When is the best time of year to prune my live oaks?

One of the most frequently asked questions I get is: when is the best time to prune my live oaks? Is there a “correct” or “better” time? Many people believe the spring is a bad time, or summer is a bad time. Are they right? Are they wrong?

The bottom line is that there’s a lot of bad, unsubstantiated misinformation circulating. To preface my answer, I am a professional, certified arborist. I graduated from Virginia Tech with a degree in forest management and I have been pruning and caring for trees for more than 18 years since I graduated, including the last 12 years in the Austin area as the owner operator of Central Texas Tree Care. We pride ourselves on solid, scientifically based, high end tree care. We have a stellar reputation from Georgetown to Buda.

As I drive to customers, I constantly encounter community signs that say “do not prune your oaks from January to June.” Local radio stations and even TV stations interviewing “experts” tell people the same thing. A search on the Internet will find articles repeating the same information. Do all Central Texas tree care companies hang up their pruning equipment for half of the year? Should they?

The answer is a resounding NO! If an oak tree needs to be pruned, it should be. The simplest and easiest way to explain this is that if an oak tree has limbs rubbing against the roof or hitting cars in the driveway, or if limbs are being broken by large vehicles driving down the street, then the tree has cracked, broken or rubbing limbs causing constant sap flow. If these broken/rubbing limbs (including crossing limbs in the canopy of the tree) are not corrected, the tree is at constant risk of infection.

Once an oak tree is properly pruned, with cuts being sealed off to eliminate sap flow, then the tree is much less likely to get infected. In fact, in all my years pruning trees in Central Texas, not only has our company NEVER had a healthy tree we pruned get oak wilt, but I have never even heard of an instance where a reputable, scientifically trained tree care company had a tree get infected with oak wilt because they pruned it.

Through my years of hands-on field experience, I have found that improperly maintained live oak trees are usually the trees that get the disease first. Then the fungus spreads through the roots to the healthy live oaks. Improperly maintained Spanish oaks are more likely to contract the disease from the beetles for the same reason.

Additionally, no scientific data exists that says leaving at-risk oak trees unmaintained is a sensible measure for containing oak wilt in Central Texas. In fact, I believe that if we pruned more Central Texas oaks to ISA ANSI-A300 pruning standards we would have less oak wilt, especially in urban areas where trees can be more realistically maintained and pruning companies regulated by municipal laws and regulations.

Native trees to consider planting in the Austin area

In order to give some guidelines for which trees to plant with success in the area, this article focuses on tree species native to the area. A separate article focuses on non-native species that grow and thrive in the Austin area, and then to non-native species that thrive here.

I am constantly asked for planting recommendations in the Austin area. Many people plant the wrong trees in the wrong place.  For example, water loving trees (riparian or swamp species) are planted in dry, sunny areas, often close to the road where radiant heat exacerbates their decline. Often trees that cannot survive in rocky soils are planted in heavy limestone. Certain trees, such as loquats or certain palm varieties cannot handle frost in the winter without being wrapped up.

Commonly planted native trees

Live oaks: The most common native Texas tree to this area is of course the live oak.   Although the common native live oaks such as the escarpment and interior live oaks are the two   common local species, the now introduced Louisianaor coastal live oaks, Quercus virginiana, are now cross-pollinating with the local species and creating hybrid live oaks.

The native live oaks are a stronger wooded tree, but much slower growing. By contrast, the virinianas are fast growing and weaker wooded warm winter live oaks. These trees are commonly planted by nurseries and builders in new neighborhoods. The hybrid species the nurseries are now selling have both the characteristics of faster growing live oaks with slightly stronger wood as well. Live oaks can live for hundreds of years under ideal conditions, with some local trees surviving for up to 500 years or more!

Cedar Elms: The second most common native species to this area is the cedar elm. This native, drought tolerant species grows among the live oaks, ashe junipers (cedars) and other trees in greenbelts. These elms have smaller leaves than other elm species, with thicker cuticles to help with the hot, dry climate. They grow thicker than the live oaks, have weaker wood physiologically, and are also less adept at compartmentalizing rot, which leads to more decay pockets in older trees that tend to be more susceptible to storm damage.  In spite of this, the cedar elm is considered the next most valuable tree to the live oak as it lives for up to 100 years or more under ideal conditions and adds considerable value to a property.

Southern red (or Spanish) oaks: I consider the Southern red oak family the next most common local native tree.  Again with much hybridization, the local southern red oak is called the Spanish oak. These trees have adapted to the local limestone slopes and are able to access the iron in the limestone. They live for well over 100 years, especially in deeper soils where they can get quite large, but are mostly found on rocky ridges and slopes where they usually stay smaller due to poorer soil. Spanish oaks growing in these conditions may be much older than they look.

Because they have thin leaves with larger surface area, Spanish oaks do much better in areas where they have shaded root zones and in greenbelts as part of a thick forest canopy. Where the sun bakes the roots, and as edge trees (see Knowledge Center article on Spanish oaks), they often get bacterial leaf scorch from too much heat and inability to retain enough water. I recommend planting them in landscaped rocky areas where little else will grow, and where they can get more water in the summer due to sprinkler irrigation or hand watering, and preferably in shady areas, although they will also thrive in deeper soils.

Texas ash: With a rounder and typically deeper green leaf, this much smaller and relatively short-lived native tree typically is characterized by a single dominant leader. Relative to other trees, this tree is fairly thin and scraggly and one of the shortest-lived native greenbelt trees in the Austin area. They typically have a 15-20 year life cycle (or less).  For this reason, you can often see many dead Texas ash trees within local greenbelt slopes. These trees grow slightly larger and live a little longer in deeper soils with irrigation, but due to their shorter life span typically lose out to other species in most local landscapes. Some native plant purists love them but not many people want to invest in ash trees versus longer lived, more valuable species such as oaks or cedar elms.

Rarely planted native trees

Escarpment black cherry: This is an interesting but rarely planted native species. Most of these trees I encounter are in natural greenbelt areas on slopes or ridge tops. We have pruned them from time to time. They have interesting bark, with lenticels (small holes that act as gas exchange) on the bark that give them an interesting look. They don’t produce fruit, and are not exactly plentiful, but do give some additional diversity.

Due to the limestone here, we have a fairly simple oak/elm/cedar forest here for the most part, with a lot of native understory plants. Some smaller trees, such as the Mexican buckeye are also present, but most of the local plant diversity seems to be in smaller trees and shrubs, and one can learn quite a few of these species by walking trails at Wild Basin, for example.

Overall and in generally favorable conditions, meaning in times of average rainfall and temperatures, any of these trees should do well if planted at your home or business. Of course it’s important to give a newly planted tree extra attention — water and often fertilization — to help ensure its long-term health and growth.

The Drought of 2011: What it means to Central Texas trees

For more than a year now we have had only a few inches of rain. Austin and the surrounding areas and even the entire state are experiencing a severe water deficit. And this isn’t getting any better, as harsher watering restrictions come into play.

No relief yet

What this means is that area trees are under serious stress, and likely will be for the foreseeable future, even as we say goodbye to the triple-digit temper- atures of summer. With the increased restrictions, a lot of trees are not getting any sprinkler water or any supplemental water, which means they are in serious trouble.

By the time the drought in 2009 was over, we’d lost hundreds of trees around the area, including scores of trees in Zilker Park. Many trees appeared to be dead, and we were unsure whether they would re-leaf in the spring. For most of 2010 we were removing dead trees, most of which were pecan trees. Additionally, some live oaks, cedar elms and other species also died and had to be removed.

During these extreme, extensive drought periods, trees that do not have additional water, are in exposed, bare soil areas (no mulch over the root zone), or are in areas that get direct sun on the root zone are extremely susceptible to decline. Radiant heat from the street, driveways, patios and other concrete features can further add to stress.

Stress spares no trees

Many trees turn yellow, many wilt and droop, and the canopies appear thinner and less robust. Trees eventually defoliate and die. All trees go into a semi-dormant state to conserve as much water as possible. Small, absorbing roots die, and then grow back when they finally get rain. Trees with higher water requirements such as maples, box elders, cottonwoods, bald cypress, willows, sycamores, catalpas, silver maples and hackberries are generally the first to die if their water supply dries up or they do not get supplemental water. The tougher native trees in water-stressed settings are the next to go.

In 2009, native pecan trees in the hottest, driest areas such as parks and dry south-facing yards died and defoliated by the hundreds. This was not something we’d seen before. We’d just assumed that these native trees were fairly drought tolerant and could handle the hot, dry summers. What we found was that during three months of 100+ degree temperatures with no rain, all bets were off. Many pecans had 50 or more percent canopy dieback, and we spent a great deal of time in 2010 removing the dead limbs in these canopies.

What you can do to minimize tree stress

So, what can be done?

Water your trees: We recommend that if you are not watering your lawn regularly, you hand water the trees once a week or once every two weeks to help keep them alive. Water only has to get down around 12 inches or so (max) below the surface soil. However, frequency and duration are the important factors during drought summers. The best way to think of it is to mimic rain when you water. Although rainwater is better for trees than chlorinated city water, as it also contains nitrogen, the important thing to note is that it saturates the soil for a prolonged period so the tree can take up enough water to make a difference. If you soak the tree for 15-20 minutes once a week or once every two weeks the frequency will also help.

Protect the root zone: Mulch: A thick layer of mulch, 2-3 inches thick is recommended around the root zone, as far out to the drip line as possible. Mulch helps keep the water in the roots, and also helps insulate the roots from the heat and keeps them cooler. Tree roots are not as deep as many people think. The anchoring woody roots go down typically no more than 2 feet. The small, absorbing roots that are responsible for uptake can typically be found in the top 8-10 inches of soil, in the Austin area they are often much closer to the surface than that.

What to do if damage has occurred

Once severe drought damage has occurred, often the limbs in the upper canopy will die. Once this happens, they will eventually need to be pruned out of the canopy, especially if they are of any size, before they fall. Sometimes we get what we call tip die-back, where smaller diameter twigs die back throughout the canopy. This is often associated with drought conditions, but also with root problems in general.

Water whenever, however you can

Water is obviously the limiting factor. Knowing what species you have and what their water requirements are is also key. Mulching to invigorate the roots and help with water retention is also recommended. Many people I talked to since the last drought had no idea that their trees needed supplemental water. Many people are having to re-think their trees water requirements, and help the trees out a little. It also helps to look up! Is the tree wilting? Losing leaves? Turning yellow? Maybe it’s time to turn on the water!