Good tree protection starts with planning. At this stage changes can be made to move buildings, parking lots, utility lines, etc. And, schedules and expectations can be established to ensure the trees get what they need when they need it and provisions can be made for after care. There are a few specific strategies that need to be articulated at the planning stage.
First, when drawings are created, plan for as much distance as possible between trees and any physical structures. It is very possible to build up close to many species of trees, but it is good practice to give the trees as much room as you can.
Talk to a few arborists before the planning is finalized. This is good opportunity to get feedback from multiple tree preservation professionals and make a decision as to who will help you manage the trees before a shovel hits the dirt. This will also allow you to budget your tree conservation efforts before you are in too deep and no monies have been appropriated.
Here is a checklist of things that should be covered before the construction process begins:
where will you get mulch to protect root zone, and get it down before activity?who will be responsible for putting up tree protection fencing?when will provide tree pruning and treatments?have a meeting with the general contractor to inform him of tree protection measures?ensure that local ordinance requirements are met and any appropriate paper work is submitted.
Putting up signs will also help with overall awareness regarding tree preservation on the construction site. This will let workers know trees are important to you and that individuals will be held accountable.
It’s a good idea to start fertilization / treatment services prior to ground breaking. For my fertilizer services we do regimented treatments that are run on a time schedule. Different treatments are done at different times of the year. Not all tree services work this way. Whether it is part of a program or one stand alone treatment. It is best to get the first application done early.
There are several facets of construction site tree protection that need to be covered. Most of the basics are pretty straight forward. Since all construction sites are different, the tricky part is understanding the impact to trees on your particular site. Some of the things you can do yourself, and some of the techniques will require you to hire a professional tree guy.
The most important part of construction site tree protection is fencing off root zone areas so construction workers don’t have access. The ideal situation would be to fence off the entire area within the tree’s drip line (the extremities of the branches reach). The tree roots definitely go out further. But, this would protect enough root zone to yield minimal damage to tree roots. In many cases, protecting this much tree root zone on a construction site is not possible, so fence off as much area as possible.
For areas that are likely to receive high traffic apply a 3-6” layer of mulch to reduce soil compaction. The thickness of the mulch will vary with the type of traffic. For foot traffic, a 3-4” layer will suffice. If heavy equipment will be driving across the root system, a thicker layer will be appropriate. If there is to be regular equipment activity, put plywood across the mulch to further distribute weight and reduce soil compaction.
Understanding that trees are going to suffer root damage during the construction process, it is important to engage a regimented fertilizer / treatment program to help the tree repair injuries. Ideally, this would start before construction begins, but it’s better late than never.
In addition to root injury, trees will typically require some pruning to allow room for the new structure and for traffic underneath. Over-pruning might be required to meet the goals of the construction project. All the more reason to fertilize the trees regularly.
The last construction site tree preservation technique I want to discuss is soil restructuring. The idea here is to till the areas of the construction site that received high traffic to un-compact the soil. Using and airspade to blow out the soil with air allow the earth to be tilled without destroying tree roots. Mixing in some finely ground mulch or other organic matter will further improve root growing conditions.
Oak wilt is a serious problem in central Texas. It kills neighborhoods worth of trees at a time. Implementing control programs is crucial, but implementing programs to plant replacement trees is arguably more important. But, what kind of trees should be planted?
Lately, the popular choices have been wilt resistant oak species: bur oaks, chinquapin (cheenk-a-pen) oaks, monterrey oaks and lacey oaks. While these are all reputable trees, they are not without their own limitations. Bur and chinquapin oaks in their natural setting are found in river bottom areas where there is substantial water available in the underground tables. Planting these trees in the hill country or on a rocky slope is not a good idea without irrigation; even then, you are testing mother nature’s boundaries. Monterrey and lacey oaks are better adapted to rocky slopes and dry conditions, but you should know that these are not tall growing trees. Monterreys get a little taller than the laceys, but both max out around 15-20 feet. And, their life span is relatively short as well. Depending on planting conditions, you should expect 20-40 years. Maybe that’s long enough for you, but come on, you are going through all the trouble to plant a tree; why not plant something that will grace the neighborhood long after you move on.
My favorite trees to plant are the natives, even the ones people shun because of oak wilt susceptibility. Live oaks and red oaks are two of the best adapted varieties of trees for the central Texas area, but many people write them off because of oak wilt. The reality is that transplanted oaks generally don’t graft roots with the natives and will survive an oak wilt onslaught. Cedar elms are another good choice for central Texas, and these trees are hardy to a large variety of growing conditions.
Live oaks and red oaks are the best trees for the area. It’s bad enough that oak wilt is killing them. We don’t the to make the problem worse by failing to replant these spectacular species. Basing your planting selection on one single tree disease is succumbing to evil’s trickery. Just because a tree is tolerant of oak wilt, doesn’t mean it won’t have other problems. And, oak wilt control is getting better all the time. With the digital age upon us, documentation and our knowledge base is improving. Mark my words, one day soon, we will be able to effectively treat and control oak wilt. Help restore our oak forests by planting new live oaks and red oaks today.
Soil restructuring is one of the most powerful tools we have for tree health management. The idea is to till the soil; improving its structure will allow valuable air and water to more easily penetrate the soil. While fundamental in gardening theory, this task is not easy at the scale of a large tree.
One of the first challenges we must deal with is maintaining tree roots while tilling the soil. After all, we are trying to help the trees here! This challenge is overcome by use of a tool called an airspade. An airspade is an over powered air compressor that blows away dirt without damaging the tree roots. There is just enough power to displace soil, but not enough to cut through roots.
In most scenarios, we will till the top 4-8” of soil depending on the site conditions. We’ll then add about 2” of finely ground mulch or other organic matter and then re-till the soil to get it all mixed up good. Once this part of the process is completed we’ll top dress it with about 4” of mulch.
The end product is an inviting soil that is great for growing anything. This is as close to mimicking a natural forest floor as we can get in an urban environment. Add a few small to mid size shrubs to provide an additional layer of shade to the soil surface and some irrigation and you’ll have a full blown tree utopia!
What is the best fast growing shade tree to plant in Austin? Here is my answer: red oak. There are several factors that must be considered, and there are special precautions you need to take. No tree is fool proof.
Red oaks grow fast to provide shade quickly, plus they are long lived and hardy. Here is a red oak 6 years after planting
The general trade off for fast growing trees is that they are shorter lived and require more maintenance, but you get shade faster. And, typically, slower growing trees live longer and tend to require less maintenance in a typical urban landscape. The red oak is a good balance. This tree has a rapid growth rate, 3-4 feet per year, and has a solid wood you would expect from an oak which makes them less prone to limb failure during storms. The norm for fast growing trees is that they have weak wood that require regular canopy thinning to reduce the likelihood of limb failure. Red oaks require very minimal pruning throughout their life, comparatively.
You do need to pay special attention to red oaks during the first few years after planting your new red oak. These trees are especially susceptible to transplant shock. Keep in mind that they have spent the first few years of their life in a tree farm that has maintained perfect growing conditions to grow trees fast. So your tree has just been relocated from a tree utopia to the virtual desert that is your yard. It is important to water and fertilize your tree properly during the first 1-3 years (read our fertilizer blogs).
Get past the first few years and you will have a fast growing shade tree that will grace your neighborhood for 75 years or more. In as little as 6 years you will have a tree that really looks like a tree, not just a stick in your yard.
There are a variety of tree fertilizers out there. Knowing which ones to use can be very confusing. And, to make matters worse, many quality tree friendly products are really “fertilizers” at all. Most of the products in the line I use for my companies treatment programs are alternative products (I don’t like the word “organic,” it is confusing to many and misleading). Here is a list of the products I think are the best:
- Fertilizers – Urea has been regarded as the best nitrogen source for trees lately. It comes in many forms, but I believe that urea-formaldehyde and methyl-based urea are the best choices. I use a product called Coron that is a methyl-based urea.
- Mycorrhizae (my-core-rize-uh) – These are fungi that grow on the existing root system of trees and then make their own root like system. The fungi then share the water and nutrients they absorb with the tree in exchange for sugars. These fungal spores are readily available to be applied to the soil. This is a great way to improve the water absorbing ability of a tree, and can be very beneficial during our hot, dry summers.
- Humates – I use a raw form of humic acid derived from leonardite. Humic acid is by-product of composting organic matter and is know to provide many, many benefits. The two most important benefits (in my opinion) are soil structure improvements and hormone balancing. We know that humic acids help break up tightly compacted soils which improves water and air penetration into the soil. Much of the hormone balancing effects are not fully understood, but I can confirm that regular use of humic acid applied both to the soil and sprayed into the canopy result in noticeably healthier trees. We use humic acid with every treatment we apply.
- Growth hormones – I’m going to keep this simple to avoid a science class article. Application of a balanced mix of growth hormones has a fantastic effect on helping foliage develop to its maximum potential and stimulating root growth. If you can find a product that has a balanced mix then go for it. But, if you don’t know what you are doing, then skip this one.
- Micro-nutrient, vitamis and enzymes – All the good stuff we need just a little of. This is like taking your vitamins. Use of these products helps both tree growth and development and improves soil health, in turn, helping the tree. A tree fertilizer / treatment program without these products is surely incomplete.
- Soil restructuring – This is a process, not a product. But, soil restructuring is one of the most powerful tools we have to help trees in extreme urban environments. The idea is to take sterile, urbanized soils and reincorporate rich organic matter back into the soil. Fundamental in garden theory, but very difficult to accomplish on the scale of a large tree.
You should have noticed in my fertilizer discussion that only nitrogen was included. There was no mention of phosphorus or potassium. It has been my experience that application of these two fertilizers don’t generally provide noticeable improvements in tree health. Due to this fact and that high phosphates cause problems with the local streams in central Texas I don’t see the point in applying these other fertilizers.
I'm Keith Brown, owner of Austin Tree Experts. This is my repository of tree knowledge. I hope you find what you are looking for. Let me know if you don't.
