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Healthy Parks, Healthy Portland

Phone: 503-823-PLAY (7529)

Fax: 503-823-6007

1120 SW Fifth Ave., Suite 1302, Portland, OR 97204

Portland Parks & Recreation Urban Forestry News and Activities 

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How to ID Tree-of-Heaven

An easy guide to identification of this highly invasive species

by Patrick Key, Urban Forestry Tree Plan Coordinator and AmeriCorps Member

Ailanthus growing along fence

 Ailanthus growing along a fence (photo by Johnson Creek Watershed).

Ailanthus altissima has many different names, including tree-of-heaven, stink tree, and Chinese sumac. In China, it is called chouchun, which literally translates as "foul smelling tree." Whatever you call it, this invasive tree has become a big problem in our region. Originally, from China and Taiwan, it proliferates and grows rapidly, often before people realize that it is a problem. Learning to identify this invader is the first step in controlling its spread. 

Tree identification, in general, can be a complicated and sometimes difficult process. Luckily, the tree-of-heaven has a some very obvious characteristics that can make recognizing it easier.

The leaves of Ailanthus are a great way to identify this problem tree. The leaves can grow to be one to three feet long and are compound, meaning that each leaf consists of a number of leaflets. In this case, the compound leaves have 11 or more pointed leaflets. The pointed shape helps to differentiate tree-of-heaven from other trees that grow in our area that also have compound leaves. Taking a closer look at the leaflet's shape will prevent confusing Ailanthus with black walnut (Juglans nigra). The leaflets have an unequal base with two to four teeth. These teeth often have one to four glands. These glands help to give the tree-of-heaven its unpleasant aroma. 

Ailanthus leaflets

Leaflets with notches, or teeth, at leaflet base (photo by National Parks Service).

With or without its leaves, the smell of broken tissue of this species can be a clue to its identity. The smell can come from the glands at the base of the leaves, but also from broken twigs. This means that the smell can help to identify this species, all year long. Some people describe the smell as rancid peanut butter or well-worn gym socks. However you describe the smell, Ailanthus lives up to its Chinese name. 

During the winter months, the bark and leaf scars are the best ways to identify tree-of-heaven. The bark can be light brown to grey, and smooth in young trees. In later years, the bark turns a darker grey and becomes rough. The leaf scars result from the tree dropping its leaves and are located where large leaves attach to the branches. They are characteristically heart-shaped due to the shape of the petiole.

Ailanthus bark

Smooth bark of young Ailanthus (photo by Iowa State University).

older Ailanthus bark

Darker and rougher bark of older Ailanthus (photo by Brandeis University).

The seed clusters of this species can be another indicator to determine species. Tree-of-heaven is very prolific and a mature female can produce between 300,000 and 350,000 fertile seeds each year. This is part of the reason that this species spreads so rapidly. The seeds are twisted samaras, or wing-shaped. They are similar to the seeds that maples produce, but are single seeds versus the maple's dual seed samaras. They often turn a reddish color as they mature, and are clustered in large groups. The seeds are dispersed during winter months, so they are a good way to identify Ailanthus once it has lost its leaves. 

Ailanthus seeds

 Ailanthus seed clusters (photo by Bill Johnson).

You can use these characteristics to identify Ailanthus, which is the first step to controlling its spread and the damage that it can do to both urban and natural areas. Keep an eye out for a second blog post about tree-of-heaven, with a focus on control methods. Also, check out Tree-of-Heaven Eradication Now! (TEN!) at for more information and resources.     


Ailanthus altissima. Wikipedia.

Alien Plant Invader: Tree-of-Heaven. City of Portland Bureau of Environmental Services.

Journey with Nature; Tree of Heaven. The Nature Conservancy.

Tree of Heaven (Ailanthus altissima). A Guide for the identification of Boston Area Invasive and Exotic Species. Brandeis University.

Tree of Heaven (Ailanthus altissima). Iowa State University Forestry Extension.

Tree-of-heaven: Simaroubaceae Ailanthus altissima. Virginia Tech Department of Forest Resources and Environmental Conservation. 

Broadleaf Evergreen Tree Tour: March 26 from 10 am to noon

Join Urban Forestry instructor Jim Gersbach for a walking tour of Irvington's unique broadleaf evergreens!

Starting Location: Caffe Destino,1339 NE Fremont St., Portland, OR 97212

When: Saturday, March 26th 2016 from 10 am to 12 pm


9:30 am - 10:00 am: Register at Caffe Destino 
9:00 am - 12 pm: Walk around the neighborhood and see broadleaf evergreen examples
Noon – Return to starting location

Register Online Here 

Irvington has some of the biggest, most beautiful, and ecologically significant broadleaf evergreen trees in Portland. Nurseryman Sean Hogan, who lives in Irvington, has long championed the use of evergreen trees in Portland, believing them eminently suited to our mild Pacific maritime climate. Since the 1990s he has been introducing to his neighbors’ yards and planting strips many species of broadleaf evergreens completely new to Oregon. As a result, Irvington has become a showcase for promising tree species seldom seen in the United States.

Citywide, broadleaf evergreens make up only about one percent of Portland’s urban canopy. Thanks to Hogan’s efforts, Irvington has Portland’s richest collection of broadleaf evergreen trees in the public right-of-way. This walk lets people see how these trees have grown, matured, and thrived in our climate. 

Just a few of the exciting trees that we will see on the walk:

bambooleaf oak Quercus myrsinifolia - boxleaf azara Azara microphylla - Chusan palm or windmill palm Trachycarpus fortunei - Compton oak Quercus x comptoniae - Edith Bogue southern magnolia Magnolia grandiflora ‘Edith Bogue’ - English holly Ilex aquifolium - Japanese chinkapin Castanopsis cuspidata - Jounama snow gum Eucalyptus pauciflora ssp. debeuzevillei - La Siberia Oak Quercus greggii 'La Siberia' - loquat Eriobotrya japonica - Mexican blue oak, Sonoran blue oak Quercus oblongifolia - olive Olea europaea - omeo gum Eucalyptus neglecta - Pacific madrone Arbutus menziesii - pineapple guava Feijoa sellowiana - Sierra oak, Canby oak Quercus canbyi - silver-leaf oak Quercus hypoleucoides - smiling forest lily tree Magnolia maudiae var. maudiae - snow gum Eucalyptus pauciflora ssp. niphophila - Southern magnolia Magnolia grandiflora - Sweet Bay magnolia Magnolia grandiflora var. australis

Contact Patrick Key at Portland Parks & Recreation Urban Forestry


Diverse Trees Planted to Replace Recently Removed Cherry Trees in Boise-Eliot

Albina Neighborhood Tree Team (ANTT) project a great success for neighbors, tree canopy and Portland

By Jim Gersbach, Urban Forestry Community Services Aide II

Boise-Eliot Tree Planting

Neighbors and volunteers help plant a boxleaf azara donated by Friends of Trees. 

Residents of Boise-Eliot planted scores of cherry trees to beautify their neighborhoods in North Portland, after World War II. Each spring, these trees brought stunning blossoms for all to see. However, as the trees aged, Boise-Eliot's streets became lined with trees in various states of demise. Besides creating a sense of blight rather than beauty, these lifeless, leafless trees no longer provided the many benefits residents would get from a living tree, such as reducing noise, moderating heat and preventing violence and crime.

Portland Parks and Recreation Urban Forestry's 2014 Street Tree Inventory revealed that more than 100 of the neighborhood's cherished cherry trees were dead or dying- due, in part, to the cost of removal and replacement. Additionally, planting of identical trees at the same time, resulted in simultaneous senescence.  

Albina Neighborhood Tree Team (ANTT), a group of city-trained volunteers, identified five qualified low-income households with dead street trees. ANTT then secured funding through the Urban Forest Stewardship Program, to hire certified arborists from local tree care company, Treecology, for tree removals, and Oregon Stump Grinding, to prepare the ground for replanting.   

The Tree Team, with approval of a city tree inspector, then decided on a diverse mix of eight replacement trees, donated by the non-profit organization, Friends of Trees. Those trees were planted by Tree Team members, Friends of Trees staff and volunteers, on February 13, 2016, as a special Valentine to the neighborhood.  

The new trees represent a healthier mix, with varied lifespans. For instance, a ponderosa pine can live for two centuries or more. Other trees planted were chosen because they bloom when nectar is scarce for pollinators, such as winter or summer. Some, like a Chinese pistache, are more tolerant of heat and drought than cherry trees, making them better adapted to climate change. Others, like a Chilean boxleaf azara, are evergreen and better suited than deciduous trees for intercepting and slowing runoff from Portland's winter rains. 

Homeowners in the area, like Aundrea Smith, are relieved that dangerous cherry trees that stood lifeless for so long were finally removed. She says she looks forward to admiring the lavendar flowers of her two new Muskogee crape myrtles for many summers to come. 

ANTT tree planting

Neighbors and volunteers pictured with a newly planted Muskogee crape myrtle, donated by Friends of Trees.

For more information about Neighborhood Tree Teams, the Urban Forest Stewardship Funding Program, or upcoming Urban Forestry workshops, please contact:

Identifying Heritage Trees in Parkrose and Parkrose Heights

This Saturday!

panorma rocky butte 

Join Urban Forestry instructors Jim Gersbach, Will Koomjian and Dave Hedberg, along with the Parkrose and Parkrose Heights Tree Teams for an exploration of potential Heritage Trees through a short presentation and neighborhood walk.

The Parkrose and Parkrose Heights neighborhoods are steeped in history and trees offer an opportunity to preserve these stories as a connection to the past. This workshop will highlight local history, Urban Forestry's Heritage Tree Program, and the process for nominating Heritage Trees.

Bestowing Heritage status upon a tree of significant horticultural, historical or cultural value imparts the greatest honor and protection that the city can provide for a tree. Learn more about this program and the magnificent trees of East Portland this Saturday. Here are the details:

    When: Saturday, March 19, 2016, 1-3pm (registration, snacks and refreshments at 12:30pm)

    Where: Parkrose United Methodist Church, Miller Hall (11111 NE Knott St, Portland OR)

    Register here or email: (971-334-0347)



Tree Podcasts Part II: Pier Park's Douglas-firs

Today we bring you the second in a series of podcasts highlighting the amazing stories behind some of Portland's historic and Heritage Trees. Produced through a unique partnership between PP&R Urban Forestry and Portland State University, the Portland Heritage Tree Podcasts were created by Caitlin Tholen, Joshua Justice and Ryan Wisnor as part of a Portland State University course on Portland’s Heritage Tree program.

These podcasts explore a few of the many trees within the Heritage Tree program as well as a few trees that are not officially designated. Visit the PSU site to find not only the podcasts, but credits and further reading on the trees. A special thanks to Bruce Rash of KPSU for his assistance in recording these podcasts.

In this episode, you will hear about the Douglas-fir trees of north Portland's Pier Park and their role in "Bloody Wednesday". On the morning of July 11th, 1934, the Douglas-fir trees acted as shields, witnesses, and later symbols to one of the most dramatic and violent scenes of Portland’s labor history. This podcast is an abridged version of a research paper written by Ryan Wisnor.

For more details on Bloody Sunday, visit Ryan's post at the Pacific Northwest Labor History Association here

For more podcasts and information on the project, visit: