Magnolias and their care in the greater Austin area

Southern magnolias, Magnolia grandiflora, are widely considered to be one of the most beautiful and sought after tree species in the Southern and even Western United States. Not only are they often extremely large at maturity, but they live for upwards of 100 years under the right conditions, and explode all summer long with the most amazingly large and striking white flowers throughout the entire canopy.

I began my care of magnolias in the Bay area of Northen California about 18 years ago. Pruning and general fertilization to these amazing trees in the deeper soils of Northern California was generally only preventive care, storm damage repair and general maintenance, as most were vigorous and healthy and not many challenges arose.

Here in Central Texas, caring for magnolias is a different issue entirely. Although the species will grow here, even in rocky soils, their needs really need to be assessed based on the site. Our soils vary widely. Some soils such as those of South and North Austin, Round Rock and Cedar Park are very rocky and riddled with shallow limestone and very little good soil. The rocky soils are very high pH (alkaline) soils. Other areas such as downtown and East Austin, and Northwest Hills have much deeper soils. Areas by Lake Austin have flat alluvial and extremely fertile soils from years of silting and produce magnificent specimens.

Having cared for them in all these areas, I must note that most of the problems magnolias have here are soil related. Additionally, compaction and lack of mulch often exacerbate already poor general soil conditions. Lack of water, in addition to one or more of these factors, is also a limiting factor in the summer months especially. Soil amendment to add topsoil and lower pH, mulching to 3 inches (max) and watering during the hot summer months are a great things to start doing if your magnolia is thinning and stunted.

Magnolias are one of those species that, in addition to their macro-nutrient requirements (N,P,K,S,Ca,Mg), they also require certain micro-nutrients in larger amounts than other species. Iron and Zinc are two of the most widely lacking micro-nutrients for magnolias in this area. Zinc, for example, is needed for the blooms. Iron is needed to prevent interveinal chlorosis (yellowing between the leaf veins). Additionally, magnolias thrive in low pH, acidic soils. Although they will grow in alkaline rocky calcareous soils, they do not get large and grow very slowly, and are of course more prone to nutrient deficiencies.

In addition to general soil amendment and mulching, yearly fertilization is also recommended. When we apply the general slow-release, granular fertilizers we use, we also add a magnolia ‘micro’ mix to add missing micro-nutrients. I have brought many magnolias back in the Central Texas area over several years, and find that they will thrive if given the right minerals, mulch, water and soil conditions, including lowering the Ph. If you have a stressed or stunted magnolia, Call us and I can prescribe a recovery plan over several years that will significantly increase the trees vitality and overall health.

Is your red oak turning yellow?

Shumard oaks are in the red oak family. The scientific name is Quercus shumardii. As one of the largest species of the southern red oak group, they are beautiful, long-lived trees that grow enormous and live for a long time, often over 100 years in the right growing conditions. They are also prized for their beautiful red fall color. They are on the list of trees recommended for the Austin area. Shumard oaks are all over downtown Austin and we have often pruned giants in the central Austin area.

That said, shumard oaks require deep soil. The central Austin area has, generally speaking, deep soils. A tree in general needs a 2 foot soil depth to thrive, although of course most of the absorbing roots responsible for the uptake to the woody conducting or anchoring roots are found in the upper 8-10 inches or less of the soil surface.

Unfortunately for shumard oaks, although they thrive in deeper soils such as Northwest hills or central Austin, they are not well suited to shallow limestone soils. Limestone holds iron in an unavailable form for many plants. When iron is unavailable to a plant, it results in interveinal chlorosis. This is basically a yellowing of the leaves of the plant, while the leaf veins typically remain green. Some water problems can manifest themselves similarly, however on shumard oaks, iron deficiency is quite severe.

The trees basically turn a bright yellow, resulting in marginal leaf necrosis (die-back), where the leaf eventually shrivels up and falls off. This leaf loss leads to chronic defoliation and death. Fertilization and iron amendments can provide temporary solutions, but are rarely recommended because they cannot take the place of inadequate soil requirements. Expensive and time consuming solutions such as soil amendments and radial trenching can be attempted, or adding topsoil and mulch over the roots in small enough amounts so as not to suffocate the absorbing roots. Generally, we recommend removal and replacement.

Often, the shumard oaks will thrive for a number of years, showing no signs of yellowing for as many as 7-10 years in some cases. Then, the trees outgrow the available soils/root ball, and hit the limestone. At this point, they yellow and go into irreversible decline. We recommend not planting a shumard oak unless you have good soil. If you are looking for a similar tree that will grow well in high caliche limestone soils, I recommend picking out a Spanish oak, which is the native Southern red oak, Quercus falcata, to this area. It has evolved to these soils, and can thrive even in high limestone, rocky Austin soil, although it grows better and is healthier in deeper soils. It also gives red fall color during leaf senescence.

Is your post oak in decline?

Post oaks have arguably the most sensitive roots of all native Central Texas tree species. On multiple occasions throughout my career, I have been called out to diagnose declining post oaks in and around the Austin area. With this particular species, it is extremely important to note that ANY root disturbance at all can lead to a very fast and most often irreversible decline. The trees quickly yellow, slowly defoliate and then eventually die. This can occur quickly or over several years, depending on the extent of the root damage.

Most post oak decline, until recently, was associated almost entirely with construction damage. Driveway and new home construction, additions and remodels, swimming pools, etc. In these instances, we were often unable to reverse or even halt the decline and bring these trees back. It is extremely Important with post oaks to try to eliminate any construction around the roots at all, or to protect as much of the root zone as possible PRIOR to construction.

As if that weren’t enough, we now have a much bigger problem. Hypoxylon canker, Hypoxylon spp., is a fungal pathogen that is now moving into the Austin area. This fungus is not new to Texas, but is now starting to wipe out post oaks in Bastrop and closer in to Austin and in rural Georgetown areas. Although this disease seems to affect mostly weakened trees, the recent droughts have exacerbated the problem by stressing post oaks everywhere, and now it is rampant. It is also an extremely fast-moving fungus, and kills and infects rapidly.

The fungus is transmitted by beetles and airborne spores from tree to tree, not by the roots. However, there is currently no cure for this disease. The only preventive measure is to invigorate the trees by invigorating them by watering them during drought conditions, and removing broken and damaged limbs from uninfected trees to help prevent/reduce avenues for infection. Removing infected trees is also not considered effective due to the extensive nature of the fugal spores in infected areas. With post oaks, once the fungus has infected a tree, eventually it kills the tree or large parts of the tree, and the bark falls off, exposing the brown fungal spores. If you touch the exposed wood at this point, you can actually see the brown very fine spores cloud up into the air. If the tree is not completely dead at this point, it soon will be.

Lightning damage can also lead to infections. It is currently still under debate as to whether the disease infects healthy trees as opposed to only stressed, unhealthy trees, although the Texas Forest Service has mentioned that increasing the wood water levels to ‘normal’ amounts can help reduce infection. Either way, I see it as a catastrophic killer of post oaks and I think that it is well on the way to eventually wiping out all Central Texas post oaks if nothing changes. I am also concerned about the susceptibility of our three oak wilt resistant species, bur, chinquapin and Monterey live oaks as they are also white oaks. I have already seen it kill a 50 year old bur oak in Austin last year.

Why should I trim my Austin trees?

Actually, the correct term is tree pruning. Years ago when I first started in the industry, I specifically remember the phrase “prune the word trim from your vocabulary”. However, for the sake of simplicity, and because it’s an important search term, we will continue calling it tree trimming for the rest of this page…

When Should a Tree Be Trimmed?

I am getting a lot of questions about whether or not a tree should be trimmed. I am one of those honest business owners who will tell you if tree trimming is necessary or not, and if it is not I will tell you not to have it done.Over pruning can do more harm than good by stripping the tree of too many leaves necessary for photosynthesis, and therefore starving the tree.

The main reasons trees are trimmed in an urban environment are:

  • Tree Safety
  • Tree Health

Other reasons include:

  • Aesthetics
  • View

Structural pruning on younger trees is often necessary to guide the trees to healthy future growth, such as training a single leader with no co-dominant stems or crossing branches. Pollarding is a highly specialized form of tree trimming that generally is used to control height and for uniformity.

Please note that general pruning to ISA pruning standards includes:

  • Class One Pruning – the finest class, which most of my customers want
  • Class Two Pruning
  • Class Three Pruning – the least of the three classes; the minimum level recommended

Check the International Society of Arboriculture (ISA) web site for detailed descriptions at

Safety Tree Trimming

Safety tree trimming comes into play when there are limbs that threaten target zones such as structures, cars or people in general. Sometimes limbs are overextended (ie. too long, often with too much end weight), crotches are weak with included bark, and/or the trees are generally very thick and heavy throughout. When some or all of these factors are present, often a tree may be hazardous and action must be taken. In most of these instances, thinning is generally an acceptable remedy, sometimes in conjunction with cable installation in the case of overextended limbs or split crotches. Some trees may be hazardous for other reasons such as rot or root damage. Sometimes limb removal or even tree removal is the only option. This is where hiring a seasoned certified arborist is crucial.

Health Tree Trimming

Health tree trimming mainly involves removing dead wood from the tree so the branch collar can close up and the tree can begin the healing process, minimizing rot in the healthy wood. This is also important because it minimizes carpenter ants which live in the dead branches on the tree and can get into your house.

Tree thinning is also often important for the health of the tree because it minimizes general splitting and the consequential wounding it can create; in particular splitting from ice storms and general thunder storms with high winds and rain. If you have been in Central Texas for any amount of time I am sure that you are familiar with both.

Other health pruning aspects include crossing branches and diseased/broken limbs. This would include mistletoe removal and removal of limbs that have been rubbing against each other and causing wounds from the constant agitation. These agitating limbs, especially on live oaks and red oaks are a cause for concern because they are avenues for infection. Knowing tree species is critical when prioritizing work, and again a seasoned certified arborist is the only way to go. If a tree is miss-identified, often it is improperly pruned.

Aesthetic Tree Trimming

An example of aesthetic tree trimming would be pruning the native ashe junipers (cedar trees) to remove dead wood. These trees have a different physiology from hardwoods and do not close their wounds when dead wood is removed. Rather, they have tannins in the wood that make the wood extremely rot resistant instead. Subsequently, dead wood removal is considered aesthetic pruning on these trees. Bald cypress would also fit this category.

Ball Moss Removal

Ball moss removal in most instances is also aesthetic pruning. Ball moss is not parasitic, but is an aerophyte (air feeder) like a bromeliad. Most of the ball moss comes out with dead wood removal. In Austin, most of the time ball moss infestations are light and standard pruning removes most of it. Generally, pruning the rest of the ball moss from the healthy limbs constitutes aesthetic pruning, because it does not negatively affect the tree. However, extremely heavy infestations (generally found in other, more humid parts of Texas) can be detrimental because the ball moss can grow to the ends of the limbs and choke out the leaves. Sometimes heavy infestations in central Texas can lead to additional limb failure during ice storms, for example due to extra weight on the branches, especially if the tree is very dense.

View Pruning

View pruning is a term that upsets many arborists (not my favorite subject either). It is not ideal and in most cases has a detrimental effect on the overall health of the tree. It is controversial. Generally, view pruning involves reducing the height of the tree to see over the top, or in the case of extremely tall trees, generally involves opening up the tree through the center to see through it.

View pruning is extremely difficult to bid, and in most cases tree care companies generally end up having to bid it on an hourly basis because it is very time consuming, generally is on slopes where brush cleanup is a nightmare, and as the trees in the front are pruned, other trees behind them are opened up and need pruning also. Most reputable tree care companies generally offer it as one of their services out of necessity. It can be done with minimum impact to the tree, but generally needs to be done yearly and in the winter for minimum impact. Aspects of height reduction such as drop-crotching and yearly pollarding are often used. I will do view pruning where it can be done with minimum impact to the trees, and do understand how a good view can impact the value of a property.

Crepe Myrtle Pruning

Not many trees grow in this soil and climate, but crepe myrtles are the exception and thrive here. There are two way to prune them. The first and best way is to thin them, remove the dead wood and crossing branches, and treat them like a small tree. This is the way most (arguably all) horticulturists would like to see it done. The second way, often referred to as crepe murder, is called pollarding.

Pollarding is when the tops of the crepe myrtles are reduced so that the plant grows to the same height every year. It is usually done for uniformity, to keep the plants all the same size and height such as medians. It is also done when growing space is restricted such as plants too close to structures or to large shade trees. Once it is started, it needs to be done yearly and in the winter, preferably January through mid February, but most years we can get away with some March pruning also.

Pollarding can be done to several species of trees also. These include sycamores, white or fruitless mulberries, fig trees. Of course shrubs are pollarded across the board (hedges). Other tree species can also be pollarded, but here in the US these are the main types.

As you can see there are many factors. I did not even talk about fruit trees. My advice to you is to call me out if you need tree trimming, or think you do. I will assess your trees, advise you on the suggested actions and give you a bid for any needed services.

Again, your trees are too valuable and you need the advice of a well-trained, educated certified arborist. Additionally, hiring a professional such as me, with a degree in the field such as a forestry or horticulture who has the educational foundation and knowledge is even more to the benefit of you and your trees. Please call me for an estimate/walk through. I’m happy to come out and take a look!

What is oak wilt?

Should you be concerned about oak wilt and are your trees at risk?

Oak wilt , Ceratocystis fagacearum, is a fungus that has been introduced to the Central Texas area since the 1960’s with devastating results. It is thought to have been in the US since the 1800’s. It is widely believed that it was originally brought in to this specific area from infected Spanish oak (Southern red oak) firewood. When a Spanish oak dies, it forms fungal mats in the Spring. These fungal mats form on the trunk wood. The nitidulid beetles (pin-head sized), feed on the fungal mats and then can then transfer (vector) the fungus to other Spanish oaks or live oaks.

Where did oak wilt come from?

This is still a mystery, but it is thought to be an introduced disease brought in from Central or South America, possibly Mexico. How? We are not entirely sure, but it could have been vectored into the United States by a sap-sucker woodpecker. These animals may have fed on a beetle carrying the spores, and vectored them into an oak tree while feeding on the sap, starting the whole process. This is, however, only a theory.

Which oak trees are susceptible?

It is important to note that Spanish oaks can only be infected by the beetle. They do not share grafted roots below ground. Live oak trees, on the other hand, do share grafted roots below the ground. So, when live oaks are infected by the nitidulid beetle from infected Spanish oaks, the disease can spread below the ground and infect other live oaks as it moves from tree to tree through these grafted roots. It can move through the roots at up to 100 feet per year, but may move slower up hills and faster down slopes.

What are the symptoms of oak wilt?

Oak wilt leaf symptoms are very prolific. The leaves form a rusty discoloration along the center vein of the leaf, which then moves out towards the leaf margins via the smaller veins. To the trained eye, this cannot be confused with anything else. Additionally, when oak wilt moves into an area, it spreads out radially from the first newly infected live oak tree in a circular pattern through the roots of the closest live oaks.

A study done at Fort Hood by Dr. David Appel, current head of the Department of Microbiology and Plant Pathology at Texas A&M shows that the beetles fly up high into the atmosphere and can be carried for miles on windy days. They then come down in new areas and form new epicenters in the direction of the prevailing winds.

It is important to note that oak wilt is often mis-diagnosed. Most live oaks that I am called out to inspect are declining due something unrelated to oak wilt. Although oak wilt is not always the cause of defoliation in oaks, always call me to check anyway. Although unlikely, oak wilt is around and if your trees do show symptoms, they need to be treated immediately for best results.

If you suspect that one of your trees has oak wilt of if oak wilt has moved into your neighborhood, contact us for a free evaluation and plan of action.

What is mistletoe and should I be concerned if I have it in my trees?

Here in the Central Texas area, mistletoe is found mainly on hackberry trees, cedar elms, and red oaks. Mistletoe is a parasite, and although it makes its own food through photosynthesis, it roots into the vascular system of the host tree and removes minerals and water from the host tree for its survival. It can be especially draining on trees weakened due to construction stresses or during droughts. If not removed, mistletoe will stay with the host tree until the tree or the limb it is on dies.

It is important to note that mistletoe only spreads from seed. It does not move through the host tree’s vascular system and send out new plants. If it is broken off, it will grow back from the existing roots in the same place. Mistletoe reaches seed in 3 years. Therefore, if we are removing it every two years, it cannot reach seed and cannot spread.

Since mistletoe is much more common and often much more severe on cedar elms than it is on red oaks, and since cedar elms are an extremely widespread and valuable tree in this area, we are often removing it from these trees as part of our pruning regimen. If stressed cedar elms have major infestations, we are often removing the mistletoe every few years in conjunction with fertilization and mulching/watering programs to re-invigorate the trees over time.

We have slowly nursed many severely mistletoe infested and stressed cedar elms back over the years. It is important to note, however, that if there are mistletoe infested cedar elms on neighboring properties, that re-infestation can still be a problem due to the spread of new seeds into the maintained trees due to birds. Birds eat the seeds and then deposit them into new trees. Squirrels can also move them around on their fur since the seeds are extremely sticky.

Mistletoe infestations can often result in swelling and subsequent weakening of tree limbs due to tissue scarring. This is also an aesthetic issue as the trees can become quite unsightly over time. As of right now, there is no product on the market that can be sprayed on mistletoe that kills the roots. There are defoliants such as Florel that can be applied, but they are expensive, have very high mix rates, and can only be applied is the winter or they will defoliate the tree as well as the mistletoe.

Dr Tom Watson, a Texas Agricultural Experiment Center urban forest researcher at College Station, has been working on a study using a plant hormone to control mistletoe (including the roots) with promising results. If successful, the product could be patented for use throughout the United States.

Vine removal in Austin trees

Customers often ask me whether or not vines should be removed from their trees. Before that question can be answered, first of all we have to identify the vines on the tree. Certain vines are much more aggressive than others.

Some vines do not climb all the way to the top of the tree. Some only go up 10- 15 feet, some go up a little higher, and some go all the way up to the top of the tree. Some vines are deciduous, giving the evergreen trees such as cedars, pines and live oaks some reprieve in the winter months.

The most destructive vine to trees in this area is the English ivy vine, which I have seen grow to the top of trees and envelope the canopy. Once this happens, the vine leaves cover up the leaves of the tree, and the tree actually slowly starves, eventually dying. Since English ivy is both invasive, fast growing, hard to contain and evergreen, this poses a serious problem for infested trees. In fact, due to its invasive and destructive nature to native plants, many nurseries have stopped selling it completely.

Extreme English ivy infestations can be costly and time consuming to remove from large trees. Vines have to be unraveled or pulled and cut off the bark with a pruning saw. If the vines are dead in the tree, they take even loner to remove because the break off in little pieces instead of larger sections.

In the Austin area the second most destructive vine to trees would have to be the mustang grape vine. Although this vine is native and deciduous, it is quite destructive and fast growing during the long growing season we have here. It can reach great heights in the tree canopy, enveloping in some cases entire trees or even groups of trees. Additionally, it gets much worse when water is continually available such as by lakes, rivers, intermittent streams and shady areas with high water tables. Many people also propagate these vines or the grapes they produce, which can be used for wines and preserves. The stems of this vine can get extremely large, up to 12 inches in diameter or larger close to the ground in extreme cases.

Another fast-growing and sometimes problematic vine is the wisteria vine. When kept to trellises and pruned repeatedly to keep it at bay, this vine can be a beautiful addition to a landscape. However, when neglected or allowed to grow up into trees or stands of trees, this vine can prove to be quite destructive. Due to its high rate of growth, it can spread through trees very rapidly, enveloping them.

Lastly, vines such as Virginia creeper and poison ivy can also get high into a tree’s canopy. These two vines are often confused with each other. Virginia creeper has 5 leaves and poison ivy has only three. Both are typically less problematic than the others listed above, but Virginia creeper also can envelope entire limbs in extreme cases and may need to be prune out of certain trees.

A little information about poison ivy is important at this point, as it can be a serious pest in the urban landscape. Poison ivy is often problematic not only due to the fact that it infests your trees, but mainly due to the sap. The plant (leaves AND stems) contains a poison (toxicodendrol) with reacts with a persons skin and causes severe rashes (rhus dermatitis) that are extremely itchy, red, raised and blistered, and may persist for, in some cases, many weeks. If swallowed or if chipped and inhaled, it can have very serious consequences. Some people are hypersensitive to it, others are immune to it. Most people (more than half of the population) get at least some reaction when expose to it, and severity of the reaction depends on amount and duration of the exposure. We recommend learning how to identify it properly and staying away from it.

If poison ivy is in your back yard or in your tree, we recommend removing it right away. Wear rubber gloves and keep out of contact with surfaces that are contaminated. Keep in mind that the sap of the vines/stems can be more concentrated than the leaves! Make sure that clothes that are in contact with the vine are washed right away and separately.

It is important to note, that if left in the yard, pets will eventually rub up against the leaves of the poison ivy, and then transfer the sap to their owners. If left in the trees, the vine continues to climb up into the canopy, making tree maintenance near impossible. It has to be removed from trees prior to pruning, to allow access to the tree.

Lastly, there are other landscape vines that can climb into trees in this area, but they are generally not problematic. Jasmine vines (star or Asian varieties) are generally not a problem because they do not climb very far up the trunks. They can be easily maintained at 6-8 feet up the tree. I have rarely seen trumpet vines or other ornamental vines that are really all that invasive either.

Keep in mind that if you do have a serious vine infestation in your trees, but do not have the budget to have the vines removed by a tree service, you can always cut them at the base. When cut at the base, the vines die in the tree, and no longer grow and continue to compete with the tree. Although often aesthetically displeasing, as the vines wither and dry up in the tree, it is better than losing a tree to a choking vine. Often in these cases, budget dictates and sometimes the trees are in a heavily wooded riparian or greenbelt area, and completely removing vines is not a priority but tree survivability is.

Trees and construction

One of the biggest challenges to local arborists and construction managers is maintaining trees on construction sites. Whether you are the construction company foreman or the homeowner, you need to do all you can to maintain and assure survivability of the valuable native trees on the construction site.

The homeowner has specific expectations around which native trees he or she wants to incorporate into the new landscape, but additionally, the local city arborist has expectations with respect to native tree survivability and tree protection. Sometimes, mistakes in the tree protection plans can shut down construction projects until the city specifications are met! I have personally seen this many times. So getting this right is crucial. This is why you should consult with a certified arborist as early in the process as possible.

Root damage

A number of factors associated with trees and construction come into play but by far the main factor is root compaction or destruction. Tree roots expand to the drip line (outer canopy) of the tree and then at least 1/3rd of the roots often extend past that. In areas where roots are restricted on one side of the tree, the roots may compensate by growing out 2-3 times past the drip line. Generally though, a municipality expects the construction company to fence off a tree’s roots to the drip line all around the canopy whenever feasible. Once fenced off, this area cannot be walked on or driven on. In conjunction, they also often recommend that this area be mulched as well, to additionally reduce compaction and reduce water loss.

The damage done to a root system by crushing the soil with heavy construction equipment can be irreversible. The problem here of course is that the damage cannot be seen and may only be realized once construction is finished. With many construction workers being unaware of the importance and shallow nature of a tree’s hidden root system, workers are simply unaware of the damage they are doing. Most of a tree’s root system only exists to two feet below the surface. Additionally, most of a tree’s absorbing roots only extend 8-12 inches (max) below the surface soil. Grading can scrape away 50-80 percent of a tree’s important absorbing roots. Add compaction and often trenching to the equation, and it’s a miracle that many trees survive construction at all!

Often, I am called in after this root damage has already been done. It is much more difficult to revive trees after construction damage, and we often loose trees at this point. Certain species such as already stressed trees or more susceptible species such as post oaks, often die even with minimally invasive construction. Trenching too close to the trunk of a tree can sever large vital anchoring roots, and lead to trees actually falling, especially in high winds/storms. This can be a serious and even deadly mistake.There is a rule of thumb for trenching close to trees; the trench should be no closer that two and a-half times the trunk diameter away from the base of the affected tree.

Vehicle compaction crushes not only tree roots, but also compacts the soil itself, having a crushing effect and reducing ‘pore space’ associated with healthy soils and optimum roof growth. This is called a ‘traffic pan’. Oxygen is reduced when soils are compacted. Water cannot penetrate as easily, permeation is reduced leading to less water absorption and more run-off. Rubber tires do more damage than tracked vehicles, because the psi is much higher due to the small amount of surface area between the rubber and the soil associated with the overall vehicle weight. On a tracked vehicle, the weight is distributed over a large track, whereas rubber tires put all the weight onto several square inches. To put the importance of compaction in perspective, even rain drops falling on bare soils add to compaction!

Tree protection plans

When a development is phased for construction, and the lots are surveyed, the trees are then inventoried. Then, certain trees are set aside as protected trees and certain trees are flagged for removal. Whether it is a commercial project or a new neighborhood, these protected trees are the ones we have to fence off and save. As municipalities are becoming more and more involved with these processes, the general requirements are also getting stricter. Compliance is mandatory from the beginning of the project to the end. Often, trees have to be fenced off prior to construction. Also, trees often have to be mulched and fertilized before construction begins, and then additionally re-fertilized after construction.

Sometimes, construction companies are required to put up bonds when they are building around large, old and extremely valuable trees. In Northern California 15 years ago, I remember a construction company killing a bonded tree in the middle of a new Saratoga neighborhood. They called me out after the damage was already done, and the tree died. The tree cost the company $20,000.00 because they did not adequately protect the root zone as required by the tree protection requirements.

Fencing off the root zone

Sometimes simple plastic fencing is required by the city to fence off the root zone, sometimes more adequate fencing is required. Some municipalities, depending on the job, require that a minimum 6 foot chain link fence be installed around the drip line. Most tree protection plans I do recommend the chain link fences, as the plastic ones are often driven over by over-zealous bobcat/heavy equipment operators. It is really difficult to successfully keep all construction crews off the root zone of a protected tree throughout all aspects of construction without putting up a more substantial chain link fence.

The problem with tree protection plans is always communication. There are scores of completely different and unrelated construction crews that are involved with all the different steps involved with the building process. It is very challenging for a construction foreman to supervise all of these different crews throughout the long construction process. Years ago when I had my house built, I had the construction foreman erect a plastic orange fence around my only front yard live oak. He would not put up a chain link fence, even though I requested it. It all went well through the entire construction process until the lot was graded in order to put down the sandy loam beneath the St. Augustine. A bobcat operator ignored the plastic fence and graded the entire root zone of the tree. I was able to stop it before it got worse, but it caused a lot of unnecessary stress to my front yard tree.

Front yard trees are almost always more negatively impacted than back yard trees. The compaction and damage to the trees in the front of the house are always associated with the majority of the heavy equipment as all of the materials are brought in from the street.

Additionally, work crews often eat their lunches under these trees. It’s much cooler under a trees canopy outside with the breeze blowing than it is inside the newly constructed building. Interestingly, even worker foot compaction to these root zones can have a negative impact on root and soil compaction, especially on bare soil.

Deep root fertilization requirements

As local Central Texas municipalities constantly refine and revise their tree protection requirements for new construction, deep root fertilization is vastly becoming an important and necessary component. Most municipalities, such as the City of Austin, for example, are now requiring pre and post-construction deep root fertilization.

Generally, the requirements are that the root zone, to the drip line, be fertilized using a pressurized, generally slow release, fertilizer mixture applied using a ‘fertilizer gun’ with a sharp tip. The fertilizer gun is essentially a soil probe with a tip that has four holes in it. The tip is inserted into the root zone of the tree at 2-3 square foot intervals, usually 5-6 inches below the surface directly into the absorbing roots of the tree.

The pressure of the system usually varies from 150 to 300 PSI. This procedure also breaks up compaction and gets additional water to the root zone. The slow release aspect is a granular fertilizer that does not completely dissolve in water, but rather breaks down over a 12 month period. This is much more effective and long-lasting than a water-based (much cheaper) fertilizer that then leaches right out of the soil after the first rain.

Oak wilt and pruning concerns

Another important factor, although generally (but not always) less severe than root destruction, are the pruning/limb removal concerns during the construction process.

Sometimes heavy equipment or large trucks break off large overhanging limbs, which need to be immediately addressed. Sometimes construction crews have to remove sections of large trees in order to erect the second stories to the building, or the rooftops/gables or overhangs.

It is always better to call in a professional tree crew quickly to take care of these issues. Having the construction crews use circular saws or jigsaws to remove limbs can lead to limb tearing or sometimes flush cutting that can not be repaired. Additionally, oak wilt concerns need to be addressed, and the cuts need to be sealed off. Also keep in mind that we can usually get a crew out to a site right away to take care of these issues, and it is often not even that expensive. Also, municipalities are starting to require that pruning by professional tree crews supervised by a certified arborist be a part of the overall tree care requirements on construction sites.


It is imperative that a good tree protection plan be improvised from the very beginning of the construction process for maximum health and survivability of all the native trees you want to or are required to incorporate into your landscape. It is very rare that I run into homeowners or construction foremen who are not sensitive or aware of the dollar value and overall aesthetic value that trees bring to a new buildings landscape. It is almost always just as important to them a that trees survive as it is to the city arborist. A large dead native tree is as devastating to the homeowner as it is the construction foreman/company.

Generally, the components that are missing on the construction site are not compassion or care, but knowledge as to how trees can be saved and what not to do to ensure survivability. Also, the communication aspect associated with every aspect of the construction process, as new crews constantly come and go.

If you can erect 6-8 foot chain link fences around the tree roots to the drip line or beyond, before construction starts, add mulch and have a pre and post construction fertilization done, the trees will survive and thrive. Additionally, have any pruning done by a professional tree crew supervised by a certified arborist. Frequently monitor to make sure the fences aren’t driven over or pulled apart and keep all foot traffic and vehicle traffic off the root zone! Trench as far away from tree roots as possible, and keep all fill soils, construction debris and material off or as far away as possible from the root zones.

Better yet, consult me first and I will be happy to discuss these and other pertinent factors associated with your specific site and concerns. Let’s keep your trees alive from the start and avoid costly tree loss and replacement requirements. It is much easier to keep trees alive at the front end of a project than try to reverse construction damage on the back end.

Squirrel damage to Austin trees

Squirrels in the Austin area are considered cute to many local Austin area residents. We like to watch them play and chase each other around the tree trunks and across the lawns. We like to watch them sun themselves on the tree trunks, and many people feed them to help promote their presence in the landscape.

This all would be great if they were not destructive to local trees and even homes! Many people do not know that squirrels destroy trees by stripping the bark off local trees and even stripping insulation from attic wiring! Often soffit and insulation damage occurs as they chew into and around the attic and roof areas.

In many parts of town, especially areas with a large urban forest, squirrel populations have exploded. With large amounts of food such as acorns and pecans, not to mention bird feeders, and virtually no natural predators, there are simply too many squirrels per acre. When the squirrel populations explode, trees suffer.

Maples, cedar elms, lacebark elms, hackberry trees, mulberry trees and red oaks all suffer damage from squirrels. They strip off the bark on the tops of limbs, sometimes ‘circumventing the cambium’ or stripping the bark off all the way around the limb, killing the branch from that point to the tips. Often they strip the bark from the upper sides of large limb crotches, drying out the limbs and weakening the unions, causing limbs failure.

In certain cases, I have even had to remove trees due to excessive squirrel damage causing large, continual and dangerous limb failure. Why do they do this? Apparently, they are eating the stored sugars made by the leaves in the summer, and that are now stored under the cambium and other cells under the bark. They often peel the bark off in strips, and may also be using it to line/weave their dens. They like the thinner, smooth barked trees and branches on the species listed above.

Squirrels do not hibernate, and may have as many as three dens they frequent at any one time. Their food sources are typically lower during the winter months and early spring, so this is when most damage occurs. Limiting and/or reducing squirrel populations is a good idea, but can be extremely difficult, time consuming and often costly. I have spoken to customers that have trapped and moved scores of squirrels with no apparent dent in the local population. Properties backing onto greenbelts are especially problematic when it comes to all wildlife, and squirrels are no exception.

In areas with fewer trees, squirrels are less prevalent and also easier to keep out of the trees. There are ways to wrap the trunks with inverted metal cones, raise low limbs, clear limbs back from roofs and sometimes separate the trees to keep the squirrels out of the canopies in these areas. Sometimes dogs in the yards also help scare the squirrels off. Keeping bird feeders out of the trees completely or putting up squirrel-proof bird feeders is also recommended. There are also several other home remedies for keeping out squirrels such as moth balls or predator urine, but that don’t always work well.

Grackle Control: Managing flying pests

Grackles are messy, black to brown colored birds that flock in large numbers in certain areas of central Texas.  They feed on garbage, generally out of dumpsters, and are extremely messy when they roost in dense trees in or near parking lots and defile the parking areas, vehicles, bus stops, etc . Grackles are becoming a vastly more severe pest problem as the years go by in Central Texas, and various methods are being explored to control them.

Years ago I attended an interesting seminar on grackle control by a Texas State Park official who worked in the Dallas area.  His area was so badly infested with grackles, that he was actually imlementing shooting off ‘whistlers’ to control grackles.  These ‘whistler’s are actually a type of shotgun shell that is fired into the air, creating a whistling sound culminating in a explosion that temproarily scares off grackle flocks from their roosting areas.  Although effective, it is loud and disruptive, and there are certain areas where this simply cannot be employed.

I have found thinning dense trees in high impact areas to be quite effective at controlling grackles. Thinning needs to be done anyway, not only to reduce potential storm damage to landscape trees, but can also be highly effective in reducing grackle roosting problems.

For example, in several instances in 2010, we thinned trees out in several different shopping centers that were having grackle infestations. After the trees were thinned, the grackles no longer had the cover of the dense foliage, and have since moved their roosts elsewhere. At the Tech Ridge Center at Parmer and I-35, the property manager was looking at installing an extremely expensive grackle control misting system to all affected trees.

This system had to be hot-wired into the ground at all tree islands in the parking lot, and was supposed to expel an irritant at certain times to repel the pests.  After thinning out the landscape trees early in 2010, we are now experiencing such a decline in grackle activity that they are not considered to be a major problem at this time.