To help the tree survive in the urban environment it is also important to select large-caliper trees. Larger caliper trees typically branch higher, providing necessary clearance sooner than smaller trees. Smaller trees are also more prone to damage and vandalism. Planting larger caliper trees of good nursery stock helps protect the investment in our urban canopy resource.
Broadleaf trees must be at least the minimum caliper size as defined below at the time of planting. Tree caliper shall be measured at 6” above the tree’s natural ground line for trees <4”, or at 12” for trees >4”.
Broadleaf tree size requirements
|Street tree minimum caliper size
|One and two family residential
Conifer tree size requirements
Conifer trees shall be a minimum of 5 feet in height at time of planting.
Trees must be grown and harvested in accordance with the standards in the American Standard for Nursery Stock (ANSI Z60.1-2004 or the most current edition). Trees acquired for planting in the City right-of-way must exhibit the following characteristics:
- Healthy and vigorous, with trunk and limbs free from insects, disease, defects, injuries, and decay
- Single trunk that is straight, with a well-developed leader and good trunk taper
- Well-distributed branches that are considerably smaller diameter than the trunk, with wide-angled branch attachments or branch attachments that are appropriate for the tree form.
- A fibrous root system
- Bareroot trees: Bareroot trees shall have abundant root growth, with both larger anchor roots and smaller fibrous roots. Roots shall not be broken, torn, decayed, or damaged. Bareroot trees shall be planted prior to bud-break.
- Balled and burlapped (B&B) trees: B&B trees shall have a firm root ball. The root ball shall not be loose, broken, or desiccated. The trunk shall be solidly attached to the root ball. The root ball shall be large enough to support the tree caliper size. Minimum root ball diameters for selected sizes of shade trees (ANSI Z60.1) shall be:
|Minimum root ball diameter (inches)
- Container trees: Roots shall be well-developed enough to hold the potting substrate together. The tree shall not be pot bound or have matted or girdling roots. The soil shall not be desiccated.
- Fabric bag trees: The trunk shall be solidly attached to the root ball. The root ball shall not be broken or desiccated.