Who hasn’t dreamed of the most grand tree house imaginable? Trap door, zip line, bucket on a pulley to get your stuff up. Well, for a few lucky kids their dream came true. And, their dad cared enough about the tree to call me in for advice. He didn’t want the dream tree house to be the demise of the tree. There are techniques to employ to minimize the damage to your tree when building a tree house.
As a landscaper, your job might not be to manage tree ordinance compliance, but planting trees from this specific list will help your client (the contractor) keep their costs down. Planting trees from the list below will count toward the tree mitigation fines.
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75% of the trees planted must be from the class one list; 25% can be from the class two list.
Quite opposite of the typical instinctive thought, putting a patio around a tree can be very beneficial to the tree. I will cover the fundamental benefit the tree receives from a patio and discuss the pros and cons of different construction materials / techniques.
The significant benefit that a tree gets from a patio is reduced soil compaction to its root zone. If there is no buffer between your feet and the soil, then the compaction that takes place over years of foot traffic becomes a very real stress factor to the tree. A patio can either reduce soil compaction by distributing the weight of your foot steps or eliminate compaction entirely by getting you completely off the ground.
Pavers are a popular choice for construction materials. They do a good job of letting soil and air penetrate the soil and do a fair job of distributing weight load to reduce soil compaction. The bigger each individual paver, the better job it will do distributing weight.
Concrete slabs do a much better job of distributing weight. Because the slab is one big piece, each foot step gets distributed over a larger area. Concrete becomes a problem in two scenarios. One, if you are covering more than half of the root system you might run into water and air exchange issues. And, if your slab requires you dig footing trenches around the edges the trenching might cut roots. However, if you slab is covering a small portion of the trees root system, then you can actually help water retention (remember that trees roots go out 4-5 times as far as the branches). Whenever it rains, the water moves laterally once it gets in the soil. So, water does get up under the concrete. However, as the sun and air dry up the water, the concrete slab will protect the soil underneath and act as an oasis of moisture after exposed soil has long since dried. I have heard and read about concrete buffer soil pH to deadly high ranges, but I have never experienced this on my projects.
The best patio construction material to use around trees is wood. Elevated wood decks get footsteps completely of the soil. And, if you provide small gaps between the boards, water and oxygen will easily access the soil and roots. In addition, the trees leaves will be able to slip through the cracks to the soil surface and retain a natural litter layer that recycles nutrients back into the soil. This is, hands down, the best way to go.
Whatever your approach, remember to leave enough room around the trunk for growth. You don’t want your patio girdling the tree trunk. And, if you have to dig piers or footers be careful. So, carry on, be careful and rest assured you are doing your tree a favor.
Quite possibly the only thing better than being under a shade tree in the summer is taking a dip in the pool. If you are planning to build an in-gound pool near one of your prized trees be careful. You are going to be digging a big hole in the ground and will likely be taking many tree roots in the process.
The kind of tree you will be working around will be a big factor regarding the amount of disturbance the tree will tolerate. For example, live oaks will take a lot of abuse; I’ve seen pools built within a few feet of the trunk of a live oak and the tree survived. American Elms, however, do not fare well after substantial root injury.
My general rule of thumb for any construction around trees has been to try and give at least 15′ of clearance from the tree trunk. If you are digging or leveling the soil within 15′ you are asking with trouble. This holds especially true when digging out for a pool.
A good thing to do before you start digging is to use an airspade and dig some trenches to find out where you have big tree roots. An airspade is a high powered air compressor that can blow away dirt without damaging tree roots. Doing a few test digs will give you an idea of how much trouble you are getting into.
Regardless of your exact proximity to the tree trunk, any trees near the pool should be put on a fertilizer regimen to help the tree repair wounds and regrow root system. Often, trees that are not right next to the pool, but adjacent to the path used for equipment access get damaged, too. Don’t forget about these trees.
High traffic areas around the pool and along the access path should be de-compacted using and airspade to restructure the soil. This is critical to providing the trees a good soil environment for the roots to regrow.
The bottom line is that pools can be built near trees without having to sacrifice the trees. But, certain steps must be taken to ensure your pool design allow for sufficient tree preservation measures. You should go into the design process with an open mind and willingness to sacrifice some pool features to save your tall green friends.
Tree care that takes place after the construction process is arguably the most part of mitigating damage from the construction process. Even if you had a great tree protection plan and follow it to the “T”, there is going to be damage done. Probably to both the canopy and especially the root system. It will take the trees years to recover from the damage. But, engaging in appropriate after care will help speed up the recovery and minimize the signs of stress.
If you haven’t already done the soil de-compaction, do it soon. This is very important for helping water and oxygen penetrate the soil surface in areas where construction activity compacted the soil. Tree roots can’t regrow without these two things.
Plan to maintain a regular fertilizer regimen for at least 2-3 years. Five years would be ideal, and I recommend some form of fertilization on a regular basis depending on your landscape and site conditions.
You basic plan should be outlined by the time construction begins. Things change during construction and your tree needs may change as well. There are a few things you should be ready to manage while construction is going on.
Ideally, tree pruning should be done near the beginning of the construction process, but after planning is finalized. At this stage you can predict what clearance pruning will need to be done and get it handled before the construction workers start hacking at what’s in their way. You’ll probably need another small round of pruning near the end of your project to tie up some loose ends.
Pay close attention to you tree protection fencing. It is going to get pushed down and you will have to put it back up. Just expect this.
You might need a treatment application during the project. For my services we do a regimented program where certain treatments are done at certain times of the year. Some tree services will simply do a once before and once afterward approach.
It is possible that adjustments to your building plan and/or layout can change in the middle of the project. Don’t forget to inform your arborist of any changes, you never know when something might affect the trees.
Watch the mulch spread under tree canopies. This mulch is there to help reduce soil compaction. If it gets moved out of place or squished into the ground, replace it. It is also a good idea to use an airspade to de-compact the soil in high traffic areas to reverse the soil compaction affects. This should be done as one of the last things before the landscaping is put down.
Don’t forget to review you post construction plants. That part is just as important.
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.
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.
