SMA Announces its 2014 Urban Tree of the Year: Parrotia persica ‘Vanessa’

The Society of Municipal Arborists (SMA), comprised of urban forestry professionals worldwide, has chosen ‘Vanessa’ Persian ironwood (Parrotia persica ‘Vanessa’) as its 2014 Urban Tree of the Year. Trees selected for this designation must be adaptable to a variety of harsh growing conditions and have strong ornamental traits. The Tree of the Year Program has been running for 18 years, and past honorees include live oak (2013), Accolade elm (2012), and goldenraintree (2011).

The Persian ironwood tree is native to the lower mountain slopes of northern Iran, and it has been planted widely in cities across Europe and North America for many years. It has great color in the spring, with glossy, green, red-tipped leaves that later turn a darker green through the summer. Fall color is spectacular, often with leaves of multiple colors on the tree at the same time: orange, purple, yellow and green. When older, this tree has flaky grey bark that is very attractive, giving it year-round appeal.

Fall leaf color. photo: Lynk media, Wikimedia Commons
Fall leaf color. Photo: Lynk Media/Wikimedia Commons.
Persian ironwood during pollination. Photo: Oregon State University, Dept. of Horitculture
Persian ironwood during pollination. Photo: Oregon State University, Dept. of Horticulture.

The cultivar ‘Vanessa’ emerged from Europe in the 1970s and is now widely cultivated in North American nurseries. ‘Vanessa’ is upright, almost columnar, with branches that arch gracefully outward towards the tip. It is a slow-growing, small tree, reaching a height of about 36 feet (11 meters) at maturity. Perhaps because of its slow growth rate, it seems that much of the available nursery stock is slightly smaller than would be typical for street tree planting programs. It is hardy in USDA zones 4-8.

In Renton, Washington, Urban Forestry and Natural Resources Manager Terry Flatley is a big fan. “We planted ‘Vanessa’ parrotia as a street tree in 4 x 8 feet (app. 1.2 x 2.4 m) cut-outs using tree grates during December of 2011; we have had 100% survival to date. They received some supplemental watering between June and September (our driest season) at the rate of once per two weeks and they showed little or no stress. We also planted one at a different site that unlike the others, did not receive supplemental watering, and even this tree has survived nicely. With its upright habit, ‘Vanessa’ fits nicely in our downtown area with zero building setbacks and along the curb-line. I plan on using more of them in the future based upon this trial planting and appreciate ‘Vanessa’s tolerance for dry, hot urban conditions.”  

In Surrey, British Columbia, ‘Vanessa’ is being planted as a street tree where there are overhead lines in close proximity to the planting strips. Staff there report that it responds extremely well to clearance pruning and has fewer crossing branches than either the straight species or the cultivar ‘Ruby Vase’. Branch unions tend to be very strong, and ‘Vanessa’ doesn’t seem to develop the levels of included bark that the staff has observed in other species of columnar trees.

Apart from its upright growth habit, ‘Vanessa’s suitability for urban use comes from its lack of major pests and its ability to tolerate both dry soils and seasonally wet ones.  

The SMA recognizes the sturdy and enchanting ‘Vanessa’ Persian ironwood for its service to urban forests and encourages its use when matched appropriately to site and as part of a diverse urban tree inventory.

Persian Ironwood. photo: Jean-Pol Grandmont
Persian Ironwood. Photo: Jean-Pol Grandmont