Roadway Standards Section 255 - Landscaping

Roadway Standards Section 255 - Landscaping

Within the public right-of-way, landscaping and irrigation shall be maintained by adjacent the property owner unless an agreement exists that requires maintenance by others.  Street trees located within landscape strips are required by the ZDO as part of development.  The number of street trees along a property frontage shall be maintained by the property owner unless otherwise approved by the County.  Approved ground cover including shrubs, plants, or grasses should be installed at the time of development within landscape strips and landscaped medians.

If installed as part of development, landscaping and irrigation are subject to a Development Permit.  Otherwise, landscaping installation compliant with Section 130.2 is not subject to a permit.  Street trees that are removed are required to be replaced if required as part of land use approval. 

The County presents guidelines for street tree installation and landscaping not subject to a Development Permit.  It should be noted that regardless of compliance with County standards and guidelines for street tree planting, the adjacent property owner is responsible for the landscaping, and per ORS 368.910 and County Code Section 7.03, is responsible for the maintenance of adjacent sidewalk and curb and any damage that may be caused by landscaping or other activities.

255.1 Topsoil

The top 6" of topsoil in the planter strips shall be a well-draining soil blend suitable for growing.

255.2 Shrubs, Plants and Grasses

1. Shrubs, plants and grasses species should comply with the County's Shrub, Groundcover, Riparian Plant List. 
2. Landscaping should be designed to minimize water consumption and utilize Oregon native plants.
3. In addition to street trees, landscape strips should be planted with a sufficient quantity and density of shrubs, plants and grasses to minimize weed growth. 
4. Irrigation should be provided unless the applicant presents a planting plan that is likely to succeed as recommended by a Landscape Architect and/or Arborist. 

255.3 Street Trees

These standards are intended to ensure that new trees planted within the right-of-way are of the highest quality, require low maintenance, and will not compromise public safety.  Comply with the requirements of Standard Drawings L100 and L200.

255.3.1 Street Tree Selection

Street trees shall comply with the Clackamas County Street Tree List.

255.3.2 Street Tree Quality at Time of Planting

1. The trees shall have a straight trunk perpendicular to the ground with a minimum branching height of four feet above the ground for trees 1 ½" caliper to a minimum of six feet above the ground for trees with 2" caliper.  No trees may be planted with a caliper less than 1 ½" except as noted below.
2. Plant material shall be grown to the current standards and specifications of the American Association of Nurserymen and American Standard for Nursery Stock.  Plant material shall be of standard quality or better, true to name and type of their species or cultivar.
3. Trees shall be provided reasonably free, as defined by nursery industry standards for street trees, from insects, decay, major structural defects and damage to the trunk, branches, and root system.

255.3.3 Street Tree Condition at Time of Planting

1. If balled and burlapped in wire baskets:
2. Trees shall have a sound root ball with a firm attachment of the trunk with the root ball.  The trunk shall not be loose, but firmly held within the root ball.
3. The size and condition of root balls shall conform to the current standards and specifications of American Association of Nurserymen and the American Standard for Nursery Stock.
4. Root balls of trees shall not be allowed to dry out at any time from the nursery to the final planting.
5. Trees shall have a well-developed root system and not be root bound or have circling/girdling roots.
6. If in a container:
7. Trees shall be free of circling/girdling roots.
8. The trees shall have been grown in the container for a maximum period of one year.
9. If bare root:
10. Shall not exceed 1 ½" caliper, measured six feet above mean ground level.
11. The roots shall not be allowed to dry out and shall be kept moist at all times from the nursery to final planting.
12. The roots shall be well established and full of live and vigorous fibrous roots along with the larger structural roots.

255.3.4 Preparation of Tree Planting Holes

1. If balled and burlapped and in wire baskets:
   1. A shallow, broad tree planting hole at least 1 ½ times the diameter of the root ball shall be excavated to a depth that will position the trunk flare level with finish grade.
   2. The inner surfaces of the excavation shall be scored or roughened to the extent necessary to encourage rooting in the native soil.
2. If bare root:
3. Tree planting holes shall be one inch wider than the spread of the roots.
4. Holes shall have sufficient depth to position the trunk flare level with finish grade.
5. A mound of native soil shall be left in the center of the hole to support the roots.  The roots shall be draped and spread in their natural position over the mound.

255.3.5 Seating of Trees

1. Trees shall be set plumb, upright, and faced for best appearance.  Broken branches should be pruned after planting.
2. The hole shall be backfilled one-half with original soil and the hole flooded with water to remove any air pockets.  After backfilling is complete, the entire planting area shall be thoroughly saturated with water to remove any remaining air pockets.
3. Mulch shall be applied to a depth of two to four inches around the tree.  Mulch shall be kept free of an area within two inches of the trunk.
4. A continuous three inches high raised berm shall be constructed around the planting hole to direct water to the roots.  The berm should be removed after one year.

255.3.6 Staking

If an anchor system is not provided per Standard Drawing L200, staking is required:

1. Hardwood stakes shall be driven firmly into the ground outside of the hole.  Care shall be taken to avoid driving the stakes through the root structure.
2. Trees shall be attached to the stakes at a height of two feet using non-binding tree ties or tree ties that are at least one inch wide to prevent damage to the tree trunk.  Ties shall be attached in a manner that will allow the tree to move but still be held firmly in place.

255.3.7 Establishment Period

If installed as part of development, the establishment period for an original tree or replacement tree shall be determined by Section 190.4.

255.3.8 Root Barrier

Any tree planted ten feet or closer to a structure, such as curb or sidewalk, shall have an engineered impenetrable root barrier installed near the structure.  The root barrier shall run the length of the planting area or the structure and reach a depth of at least 18 inches.

255.4 Sight Distance

Proposed landscaping shall comply with the sight distance standards of Section 240.  If in question due to marginally adequate vertical or horizontal curvature, landscaping designers shall be required to provide evidence that proposed landscaping will not grow to become sight hazards.