The trees of Rock Creek Park are Washington's living monument to the benefits of preserving a wilderness in the city.
When Rock Creek Park was established in 1890, urban parks and national parks were new concepts. Not only was this space going to be both, it was also to be preserved largely as wilderness. Our forested valley therefore represents a kind of monument to the value of wild woodlands in an urban setting.
Many trees in the Rock Creek valley date back to the park's earliest days — and a few tall oaks may have started as acorns 250 years ago. Yet we continue to learn more about the benefits of having hundreds of wooded acres in the city. Trees improve the local climate, reduce air pollution, conserve water and support a wide diversity of plant and animal species. A forest can create a feeling of well-being and forge connections with nature not available along urban streets.
Forests of Change
Watch the trees and you can detect how Rock Creek Park changes from place to place, from season to season and over the decades.
Species usually found miles apart are just a short hike away because the park straddles the boundary between the Piedmont and Coastal Plain. Much of the woodlands are dominated by oaks, tulip trees and American beech. But descend to the flood plain and you will find sycamore, ash, pawpaw, cottonwood and other lowland species.
Spring bursts forth each year with the blooms of the redbud, dogwood, pawpaw, sassafras, tulip tree and American elm. Everywhere new leaves glow a golden green.
In summer, the mature canopy throws a veil over the forest floor. The leaves seem to capture all the sunlight, soaking in energy needed to produce nuts, fruits and berries of all shapes and hues.
It is still just August when the tulip trees are first to drop their leaves. Soon patches of sky not visible since April begin to appear. Bright crimson breaks out on the leaves of the black gum, kicking off an autumn pageant of color that echoes through the forest.
Winter allows us to admire the variety within the park's barks. We observe distinctive textures. Peeling birches. The American hornbeam, whose sinewy and unyielding exterior earns it the nicknames of musclewood and ironwood. The Shingle Oak — once used, yes, to make shingles. We also see the colors of the trunks and branches standing out against the sky and snow, from the pewter of the American beech to the cinnamon brown of the river birch.
Branches of History
The primary forest that greeted English colonists was largely chopped down during the 18th and 19th centuries for logging, to clear land for farming and to provide an unobstructed view from the many Civil War fortifications. More trees fell when the park's borders were first defined, as property owners hurried to make money from timber on their land before having to hand the property over. Rock Creek commissioners went to court to outlaw tree cutting and hired two policemen to patrol the area.
Since the 1890 Rock Creek Park law called for "the preservation of all timber," most of the trees were then left undisturbed. However, official policy has not been totally hands-off. Early park authorities viewed with disdain the Virginia pine — at the time, one of the most common tree species. Their efforts to remove these native trees provoked President Woodrow Wilson to write a letter in 1920 complaining: "in one part of the park a whole plantation of young pines have been cut down and it made my heart ache to see it."
For ten years beginning in 1911, the US Forest Service planted thousands of non-native trees — including the California redwood — at an experimental plot on the north end of the park. The Service proposed to further develop the site as botanical gardens and a national arboretum. After that plan was rejected, more than 150 species of non-native trees were removed.
Other changes have altered the canopy. The red cedars that were quick to sprout in former farm fields were just as quick to die out — overwhelmed perhaps by the Japanese honeysuckle planted to reinforce the banks of park streams. Other invasives like English ivy similarly smother the trees. Non-native fungi and insect pests have endangered or wiped out various chestnut, beech, oak, hickory, hemlock and dogwood species.
Deer represent one of the biggest threats to today's trees. Due to over-population, the white-tailed does and bucks eat all the young trees as they sprout — preventing the forest from regenerating and threatening the food sources of native wildlife.
Climate change is another modern menace. Warmer temperatures favor some species while threatening others — and provide a more welcoming environment for destructive insects and diseases. As the calendar of seasonal change begins to shift, migratory birds may no longer find the proper food or shelter when they arrive. More extreme weather means more frequent droughts and storms.
Yet, despite all these challenges, the woodlands endure, wild and alive, bringing nature to the heart of Washington.