Robert Simpson public domain

Section of Long Island following Hurricane Sandy photographed by U.S. Coast Guard Petty Officer 2nd Class Rob Simpson. Photo in the public domain.

by Michelle Sutton

The 2016 Atlantic Ocean hurricane season officially began June 1, with meteorologists offering varying opinions about how much activity we in the eastern U.S. will see. Hurricane Sandy (October 2012) savaged tree populations with both high winds and flooding. Sandy brought one storm surge of salt water that retreated with the same day’s tides. What were some of the impacts and lessons learned? We hear from a veteran arborist on Long Island and from a former NYC urban forester.

What are the major reasons flooding is so punishing for trees? Dr. Kamran Abdollahi, professor of forest ecophysiology in the urban forestry program at Southern University in Baton Rouge, Louisiana, explains that flooding fills soil pores, denying tree roots access to the oxygen they need for respiration and water and nutrient uptake. Dr. Abdollahi says, “In the urban environment where soils are already compacted by human activities, flooding exacerbates compaction and its negative effects. Flooding can also negatively affect root anchoring and tree stability.”

Long Island
Arborist Joel Greifenberger is the owner of Valley Tree and Landscape in Long Beach, Long Island. Valley has planted more than 25,000 trees for NYC in over 25 years. Greifenberger says that on Long Beach, Hurricane Sandy brought several feet of salt water on land, “bay to ocean,” for about 12 hours. That brief flooding event left dramatic damage to the region’s trees, with some surprising victims.

London plane Courtesy Cornell Urban Horticulture Institute

London plane trees, once thought to be salt tolerant, fared poorly on Long Island and in NYC after Hurricane Sandy. Photo Courtesy Cornell Urban Horticulture Institute

The biggest shock was how poorly Long Island’s many London plane trees fared. They were long thought to be flood and salt tolerant and had been widely advocated for seaside use. Greifenberger says the damage manifested in stages; the following spring, an average of a third of the canopy was affected. “It wasn’t typical dieback,” he says, “in that it didn’t affect the whole crown. A large section of the crown on one side would not break bud, while the rest leafed out normally.” However, over the 2013 growing season, the trees continued to show signs of decline, until by 2014 their bark started to peel off and the trees died.

In the summer of 2014, Long Beach took down more than 1400 dead trees. “My guess is that 85% or more of them were London planes,” Greifenberger says. “We used to have our streets lined with allées of them, like American elms back in the day. This was a huge blow to our city.” He says that the city will avoid planting monocultures in the future, no matter how flood-tolerant any one tree species is thought to be.

Arborvitaes in his area were instantly killed by the floods, as were blue atlas cedars. “I had a job where I’d planted 200 blue atlas cedars at 4-inch caliper,” Greifenberger says, “and they were at 7-inch caliper when the storm came; they were dead within weeks. That was heartbreaking.” Leland cypresses also were quick to die. Tulip trees never put leaf on again. Every single Japanese maple died. Pine trees and magnolias were a mixed bag. Across species, mortality was high for newly planted/younger trees.

In the “happy surprises” column, Greifenberger says, “Blue spruces, for one, never looked better; no one expected that! Junipers and red cedars did fine, as did holly trees. The Kwanzan cherry trees did ok if they’d been in the ground at least three years. Honeylocusts and pears did ok, and Norway maples and zelkovas did well.”

New York City
New York City lost 10,926 trees to storm damage from Sandy and shared with Long Island the experience of significant die-off of London plane trees. NYC Parks and Recreation prepared a report after Sandy related to flooding. With regard to London planes, more than 1500 failed to leaf out at all the following season and more than 2500 leafed out 50% at best, with further decline anticipated.

Flooding can contribute to root instability Courtesy NYC Parks Recreation

Flooding can contribute to root instability Courtesy NYC Parks Recreation

Part of that report asks, “How will we change what we plant because of Hurricane Sandy?” Former NYC Parks and Recreation Director of Street Tree Planting Matthew Stephens said, “Sandy highlighted that we as urban forest managers must continue to be vigilant in our efforts to specify trees that will be resilient to not only a diverse array of urban factors, but also changing environmental factors. For example, going forward, trees we choose to plant within the advisory flood zone for a one percent storm must be tolerant of both coastal conditions as well as inundation.” To give you an idea of how important this consideration is, fourteen percent of NYC streets fall within the advisory flood zone.

Integrating what was learned from Sandy’s particular toll, Stephens and colleagues identified a list of 75 tree species and cultivars that the City considers worthy of use in the advisory flood zone for a one percent storm (also known as a 100-year storm). “Every new tree planted within the flood zone will now be chosen from the refined palette to ensure our trees are long-lived and resilient,” Stephens said. That list follows.

Species Common Name
Acer campestre Hedge Maple
Acer campestre ‘Evelyn’ Evelyn Hedge Maple
Acer campestre ‘Metro Gold’ Metro Gold Hedge Maple
Acer ginnala ‘Flame’ Flame Amur Maple
Acer ginnala ‘Ruby Slippers’ Ruby Slippers Amur Maple
Acer rubrum ‘Red Sunset’ Red Sunset Maple
Betula nigra ‘Duraheat’ Duraheat River Birch
Betula nigra ‘Heritage’ Heritage River Birch
Carpinus betulus ‘Fastigiata’ Columnar European Hornbeam
Celtis occidentalis Hackberry
Celtis occidentalis ‘Magnifica’ Magnifica Hackberry
Cercis reniformis ‘Oklahoma’ Oklahoma Redbud
Crataegus ‘Crimson Cloud’ Crimson Cloud Hawthorn
Crataegus crusgalli var. inermis Thornless Hawthorn
Crataegus ‘Lavellus’ Lavellus Hawthorn
Crataegus phaenopyrum ‘Washington’ Washington Hawthorn
Crataegus viridis  ‘Winter King’ Winter King Hawthorn
Cryptomeria japonica ‘Yoshino’ Yoshino Cryptomeria
Eucommia ulmoides Hardy Rubber Tree
Ginkgo biloba ‘Autumn Gold’ Autumn Gold Ginkgo
Ginkgo biloba ‘Magyar’ Magyar Ginkgo
Ginkgo biloba ‘Princeton Sentry’ Princeton Sentry Ginkgo
Gleditsia triacanthos var inermis ‘Shademaster’ Shademaster Honeylocust
Gleditsia triacanthos var. inermis ‘Halka’ Halka Honeylocust
Gleditsia triacanthos var. inermis ‘Imperial’ Imperial Honeylocust
Gleditsia triacanthos var. inermis ‘Skyline’ Skyline Honeylocust
Gymnocladus dioicus Kentucky Coffeetree
Gymnocladus dioicus ‘Espresso’ Espresso Coffeetree
Gymnocladus dioicus ‘Prairie Titan’ Prairie Titan Coffeetree
Juniperus chinensis ‘Hetzi’ Blue Hetzi Juniper
Juniperus virginiana Eastern Red Cedar
Koelreuteria paniculata Golden Rain Tree
Koelreuteria paniculata ‘Fastigiata’ Columnar Golden Rain Tree
Koelreuteria paniculata ‘Rose Lanterns’ Rose Lanterns Golden Rain tree
Lagerstroemia indica ‘Muskogee’ Muskogee Crepemyrtle
Maackia amurensis Amur Maackia
Maackia amurensis ‘Starburst’ Starburst Maackia
Malus cultivars Crabapple
Metasequoia glyptostroboides Dawn Redwood
Metasequoia glyptostroboides ‘Gold Rush’ Gold Rush Dawn Redwood
Nyssa sylvatica Blackgum
Nyssa sylvatica ‘Forum’ Forum Blackgum
Nyssa sylvatica ‘Red Rage’ Red Rage Blackgum
Quercus acutissima Sawtooth Oak
Quercus bicolor Swamp White Oak
Quercus macrocarpa Bur Oak
Quercus muhelnbergia Chinkapin Oak
Quercus phellos Willow Oak
Quercus robur English Oak
Styphnolobium japonicum ‘Princeton Upright’ Princeton Upright Sophora
Styphnolobium japonicum ‘Regent’ Regent Sophora
Syringa ‘China Snow’ China Snow Lilac
Syringa reticulata Japanese Tree Lilac
Syringa reticulata ‘Ivory Silk’ Ivory Silk Lilac
Taxodium ascedens ‘Nutans’ Nutans Baldcypress
Taxodium distichum Baldcypress
Taxodium distichum ‘Shawnee Brave’ Shawnee Brave Baldcypress
Ulmus ‘Accolade’ Accolade Elm
Ulmus americana ‘Princeton’ Princeton American Elm
Ulmus americana ‘Valley Forge’ Valley Forge American Elm
Ulmus ‘Frontier’ Fronteir Elm
Ulmus ‘Jefferson’ Jeffeson Elm
Ulmus ‘Morton Glossy’ Triumph Elm
Ulmus ‘New Harmony’ New Harmony Elm
Ulmus ‘New Horizon’ New Horizon Elm
Ulmus parvifolia Chinese Elm
Ulmus parvifolia ‘Allee’ Allee Chinese Elm
Ulmus parvifolia ‘Bosque’ Bosque Chinese Elm
Ulmus parvifolia ‘Dynasty’ Dynasty Elm
Ulmus ‘Patriot’ Patriot Elm
Ulmus ‘Pioneer’ Pioneer Elm
Zelkova serrata  ‘Mushashino’ Mushashino Zelkova
Zelkova serrata ‘Green Vase’ Green Vase Zelkova
Zelkova serrata ‘Village Green’ Village Green Zelkova
Zelkova serrata ‘Variegata’ Variagated Zelkova
Zelkova serrata ‘Wireless’ Wireless Zelkova