The city of Austin heritage tree ordinance was adopted back in February of 2010. The new ordinance expands upon the existing tree protection ordinance creating a new “class” of protected size tree. The idea of a heritage tree is that some trees are so large and significant that they warrant special attention.
Under the new heritage tree ordinance, a heritage tree is defined as a tree 24” DBH and larger. Also, to qualify as heritage, the tree must be one of the noted species. Otherwise it remains as a standard level of protected tree. See the special species list at the bottom. I’ll explain later what a “standard” class of protected tree is. The basics on how a heritage tree must be treated to meet preservation criteria is really not at all different than the requirements for preserving a standard class protected tree. The difference is that fines for heritage trees are more. Heritage trees measuring 24-29” DBH are carefully scrutinized by city staff. Heritage trees 30” DBH and larger are referred to as “public hearing trees” and they MUST meet tree protection criteria, and any variation from this must be approved by the environmental review board and meet special criteria.
The previous (and still existing) tree ordinance titled “Tree and Natural Area Protection Code” was adopted in 1983. Its details outline the regulations for what I’ve been referring to as “standard” class of protection and defines what we refer to as Critical Root Zone or CRZ. Actually the ½ CRZ is the primary area we worry about.
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Protecting the root zone of a tree doesn’t necessarily mean you can’t build within the protected root zone area. Although, the trees might prefer that you don’t. Creative techniques that would allow you to develop inside the 1/2 CRZ will vary by site. Condition of the tree, construction plans and landscape are all factors that will ultimately determine how you build around a heritage tree. I’ve found nearly every site to be different. For certain, you are going to need a good arborist with experience working in construction site tree preservation if you attempt to build inside of the 1/2 CRZ of a heritage tree. City staff is not going to accept arboriculture recommendations from somebody who is clearly not an arborist.
Summary of Tree Size Definitions
| site type | protected size | species | protection class |
|---|---|---|---|
| commercial | 8-23” DBH | any | standard |
| residential | 19-23” DBH | any | standard |
| comm./residential | 24-29” DBH | special | heritage |
| comm./residential | 30”+ | special | public hearing tree |
List of special species:
texas ash, bald cypress, cedar elm, american elm, texas madrone, big tooth maple, all oaks, pecan, arizona walnut, eastern black walnut.