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Why are there approved street tree planting lists?
Approved planting lists are part of routine, responsible urban forest management. The lists are to help ensure the species selected for planting are appropriate for both the specific site and Portland’s urban canopy as a whole. We call this the “right tree in the right place.” The goals of the approved street tree planting lists are to encourage diversity, prevent infrastructure conflicts, and maximize the benefits of the urban canopy.
What if I want to plant a tree that is not on the approved street tree planting list for my site type?
When you get a permit to plant a tree in the City right-of-way, you will be assigned an Urban Forestry Tree Inspector to visit your site and determine where the tree can be planted. The Tree Inspector will also be the one to approve your final species selection. If you want to plant a tree that is not on the approved street tree planting list for your site, talk to your Tree Inspector about alternate options. Tree Inspectors may approve additional species that are appropriate.
If you are planting street trees with Friends of Trees, these are according to permits issued by Urban Forestry and all trees that they offer have been approved and can be planted in the appropriate site type.
How are the approved street tree planting lists determined?
Species are approved for planting based on several criteria, including: the space available for planting, status on the Portland Plant List, threats of pests and disease, how the species has fared in the urban environment in the past, current canopy diversity, climate considerations, and desirable tree characteristics.
Certain species are approved for planting sites of specific sizes in order to maximize tree benefits while minimizing potential infrastructure conflicts, such as sidewalk damage from tree roots. Trees on the Nuisance Plants List, specified in the Portland Plant List, invaders of Portland’s natural areas, are not approved for planting in City rights-of-way. Trees that are susceptible to pests and diseases are also not approved for street tree planting. Examples include elm trees that are susceptible to Dutch elm disease.
Who created the street tree planting lists?
Creation of the street tree planting lists was a collaborative process involving Portland Parks & Recreation, the Urban Forestry Commission, the Bureau of Environmental Services, Friends of Trees, and representatives from the nursery industry, local tree care experts, and the public.
When are the approved street tree planting lists updated?
The approved street tree planting lists are updated approximately every 3-5 years.
Why are maples not approved for planting in the City right-of-way?
Maples are currently overrepresented in the City of Portland, making up 28% (+ 5%) of Portland’s street tree population and almost 29% of the park tree population, according to Urban Forestry’s 2007 Urban Forest Canopy Assessment. Ongoing inventories across the city indicate that the percentage of maples in the street tree population varies between 22% and 45% per neighborhood.
These figures are disproportionately high, creating a significant risk that any pests affecting maples will catastrophically reduce the city’s tree canopy. Decreasing the dependence of Portland’s urban forest on maples and increasing its diversity will help protect the forest from significant future risks. In order to prevent a catastrophic canopy loss, PP&R Urban Forestry is encouraging planting diverse trees throughout the urban forest, not just in the City rights-of-way. This is an important step toward creating a healthier and more resilient urban forest in the long term.
What are the specific threats to maple trees in Portland?
Of current concern is the threat of Asian longhorned beetle (ALB). Portland is one of three U.S cities with the highest ALB infestation potential, according to the US Department of Agriculture Animal and Plant Health Inspection Service. ALB has already been found in Oregonbut thus far has been contained. ALB attacks all species of maples and several other hardwood genera, killing healthy trees within a short number of years. There is no known cure for ALB, and the only available management remedy is removal of infected and susceptible trees.
Maples are also susceptible to anthracnose, a fungal disease that can cause repeated defoliation and lead to declining tree vitality.
Will maples be allowed for street tree planting in the future?
Maples may be included in the approved street tree planting lists in the future if canopy or inventory studies show that maples are more appropriately represented in the City’s urban forest.
How do I use the approved street tree planting lists to select the right tree for me?
There are many great planting options on the new approved street tree planting lists. First, submit a planting permit application to Urban Forestry. An Urban Forestry Tree Inspector will inspect your site and send you the approved street tree planting list that is appropriate for your site. Select a tree from the approved list and notify your Tree Inspector, and he will issue your planting permit for that tree.
The new approved street tree planting lists offer a diversity of choices. Tree characteristics such as fall color, showy flowers, fruits/nuts for wildlife, and interesting bark, as well as native and evergreen trees, are distinguished so you can easily select a tree that has the qualities you’re looking for.
If you would like to plant a species that is not on the approved list for your site, your Urban Forestry Tree Inspector may approve an alternate species if it is appropriate for the site size and urban conditions. You can do your part to help increase the diversity, interest, and resilience of Portland’s urban forest by picking a less common tree to plant in your planting strip or yard.
Can we expect to see limitations on planting other trees in the future?
The species allowed for planting on City property will change over time due to management needs. The threat of foreign pests may precipitate restrictions on planting certain species in the future. However, the magnitude of the threat also depends on the abundance of the host species. Our urban forest managers will consider the threat of pests and disease and current and future tree species composition when evaluating the need to restrict planting of certain species on City property.