File Photo: This tree on Queen Anne Boulevard was one of 24 removed at the order of Seattle Parks and Recreation Department because it was either diseased or dying. New trees will be planted this fall.
File Photo: This tree on Queen Anne Boulevard was one of 24 removed at the order of Seattle Parks and Recreation Department because it was either diseased or dying. New trees will be planted this fall.

The Seattle Parks Department has developed a plan to replace 24 trees that were removed from the historic Queen Anne Boulevard last fall.

The trees, including chestnuts, maples and birches, were cut down after a parks department arborist determined last summer that they could not be saved because they were diseased, dying or, in some cases, already dead.

Kevin Bergsrud, Parks and Recreation Department senior specialist with the planning and development division, updated the Queen Anne Community Council last week about the efforts to replace the trees on Queen Anne Boulevard. Following the trees’ removal last October and November, a certified arborist and a consultant partnered to identify suitable tree replacements using a list adopted in 2012 as a guide.

Certified arborist Nicholas Johnson said in the presentation that when it came to selecting the replacement trees, in some cases they had to deviate from the 2012 list because they were no longer suitable.

“There’s a lot of complexity to figuring out what would be appropriate, where,” Johnson said.

In some instances, Johnson and the consultant agreed replanting with the recommended tree was impossible because they would not have survived.

“We found a lot of diseases in a lot of the trees [removed] that would prohibit planting a lot of those trees on the group list,” Johnson said. “They would kill them or make it incredibly hard for the new trees to get established.”

Of the 24 trees removed, nine will be replaced with trees identified on the 2012 list, while 15 will be replaced with new trees altogether.

Johnson said climate change — hotter and dryer summers — is a major contributing factor.

“We’ve just been having summers that are a lot dryer and hotter than the trees here are used to,” Johnson said, adding that, at the same time, that climate change is allowing diseases or pathogens that would otherwise not be a problem to survive and attack trees or contaminate soil.

In one case, a ginkgo biloba tree will be planted instead of the originally recommended sweetgum because the ginkgo is drought and heat resistant.

In another location, an apple serviceberry tree will be planted instead of a black birch because  birches have been ravaged by bronze birch borers in the Puget Sound. Plus birches are not drought tolerant and do not adapt well under power lines.

In five locations, Oregon oak will be planted instead of the recommended maple trees because the maples are susceptible to several pathogens, including “sooty bark,” which was found in the soil where the original trees were removed last year. The Oregon oaks, on the other hand, are drought tolerant and will provide a solid canopy.

“They are quite a bit tougher and resistant to heat and drought stress than the maples are,” Johnson said.

Lastly, dawn redwoods will be planted where eight dead or dying Chinese Chestnuts were removed last year. Initially, the chestnuts were supposed to be replaced with scarlet oaks.

Johnson explained, while oaks were the best option for planting in other locations along the boulevard, they were not ideal for the remaining eight sites.

The trees removed from those sites last year all had root decay caused by Kretzchmaria duesta, an aggressive organism that attacks deciduous hardwood trees like Chinese chestnuts and scarlet oaks.

“So, any hardwood tree we would replace in that area would likely be susceptible to getting that disease,” Johnson said.

While dawn redwoods do not look like scarlet oaks, they won’t be targeted by Kretzchmaria duesta because they are softwood.

“In some of the zones, we have diseases that act only on maples, so an oak tree would be a suitable replacement at that site,” Johnson explained. “In another zone, the oak trees are being attacked by a disease that prefers deciduous hardwood trees, so in those areas they’ll be replaced with softwood.

“So we’re increasing some of the diversity of the trees to decrease their likelihood of succumbing to some of the diseases found in that zone.”

Unfortunately, Johnson noted, the trees that will be planted in the coming months won’t reach maturity for many years, and could take 60 to 80 years to reach the same stature as those removed.

The city will be watering and maintaining the newly planted trees, however, Johnson said.

“We’re being very aggressive about our practices while establishing newly planted trees,” Johnson said. “It’s getting harder to establish trees, so we’re planting fewer trees, and we’re spending more time watering and caring for them.”

Queen Anne Community Council Parks Committee Chairperson Don Harper said he was pleased with the final report presented at the meeting as it demonstrates the parks department team members responsible did the best they could.

“This is all sort of uncharted territory,” Harper said. “This is a new problem. They’re on the cutting edge of trying to find trees that will grow and not be affected by the changing climate and not allow these new bugs to exist here.”

Because Queen Anne Boulevard is a designated historic location, the city’s Landmarks board must approve the changes to the tree replacement list. After that, Johnson can source and then purchase those trees and hire a team to plant them. It is possible he can move forward with the purchasing and planting of the replacement trees the Landmarks board already approved, Bergsrud said.