Among the grandest trees in nature is the mighty oak. It is a symbol of strength, longevity and endurance.
It is no wonder that a member of the Quercus family was singled out for use on sacred ground — the 16-acre World Trade Center site.
More than 400 swamp white oak trees are being planted in the eight-acre plaza, part of a memorial to honor the victims of the terrorist attacks of Sept. 11, 2001.
It’s fitting and symbolic to find new life at ground zero as this urban forest takes root at the national 9/11 memorial in downtown Manhattan.
An enduring symbol
More than 600 oaks can be found under the family name Quercus, which includes evergreen, semi-evergreen and hardwood trees.
Of these, 90 are native or naturalized in North America.
Oaks range from 3-foot-tall shrubs to trees towering 120 feet tall.
Leaves are mostly lobed and leathery. Trees classified as “white oaks’’ are marked by rounded leaf edges and edible acorns that mature in one year.
Red oaks have pointed leaf lobes and acorns that mature in two years. Acorns from red oaks are too bitter to eat — at least by humans.
Oaks thrive in deep, damp, well-drained soil. Some prefer full sun while others like partial shade when young.
Common Midwest oaks include scarlet oak, pin oak, English oak, northern red oak, black oak, white oak, burr oak and swamp white oak.
So why, out of all the oak trees, was the swamp white oak selected for the 9-11 Memorial?
“Swamp white oaks are hardy. They put up with a lot of water and poor soils,’’ said Scott Jamieson, a vice president of Bartlett Tree Experts, which has raised the ground zero trees for five years in New Jersey, about 40 miles from the World Trade Center site.
Bartlett, which has an office in Grand Rapids, will care for them for at least two years at the National Sept. 11 Memorial.
“We don’t have a national tree, but the oak is solid and known for its strength,’’ Jamieson said in an article published this month in a Des Plaines, Ill., newspaper.
This is not your typical grove of trees. Each of the 450 swamp white oak trees uses a GPS system to monitor each tree’s health, care and size.
Swamp white oaks were selected for their durability. They are “tough as nails,’’ said Wayne Dublin, vice president of Bartlett Tree Experts.
An outside enemy
Sure, it is a tough tree, but it is not indestructible. Oak anthracnose can be damaging to individual trees but is generally not fatal. It is susceptible to the oak wilt fungus.
Oak wilt disease has been of growing concern in Michigan due to recent outbreaks that seem to target red oak trees. White oak trees are also susceptible, and infected trees may take 2-3 years to die.
“I believe it has been found in most counties in the Lower Peninsula of Michigan,’’ said Georgia Donovan, president of the Kent County chapter of the Izaak Walton League, which has hundreds of oaks on its property in Kent County’s Cannon Township.
“Typically the leaves turn brown at their tips then further down the leaf and the tree’s crown turns brown from the top down,’’ Donovan explained. “When the tree detects the presence of the fungus, it reacts with gums and resins, hampering the tree’s ability to transport water up into the branches, causing the wilt.’’
The disease is commonly spread when roots of an infected tree touch and grow into the roots of a neighboring tree. It also is spread by picnic beetles, which feed on the sap of damaged or freshly pruned oaks and transmit the disease to uninfected oaks.
This is the main reason you should not prune oak trees in warm weather — from April through August.
Despite outside threats, oaks remain giants in the forest and urban landscape.
English poet and clergyman George Herbert once said storms make oaks grow deeper roots.
The same can be said for America’s spirit since that fateful September day.
E-mail John Hogan: firstname.lastname@example.org