“We are at the volatile beginning period when all the plants are fighting it out. We have to help the newly planted grasses dominate,” said Larry Weaner, Larry Weaner Landscape Associates, at the kick-off of the restoration of the 9-acre meadow at Dumbarton Oaks Park in Washington, D.C. The first two meadows in a five-meadow necklace have already been seeded with warm season grasses, embedded in a protective layer of grasses that will later die back. In a carefully-sequenced succession, the new warm season grasses will slowly take over, restoring the original vision of landscape architect Beatrix Farrand, who designed the park in the 1920s and 30s, and creating rich wildlife habitat in the process.
Liza Gilbert, ASLA, one of the leaders of the restoration process at Dumbarton Oaks Park Conservancy and the latest landscape designer to be appointed to the U.S. Commission on Fine Arts, said Farrand meant the 27-acre landscape to be a “wild garden” distinct from the formal gardens of Dumbarton Oaks just up the hill. “There is a progression of spaces, with narrow paths leading to grand vistas. She was a master of creating spatial experiences, moving from dark to light.” The land had been used as a farm for decades; Farrand “created a paradise out of land that had been worked.”
Farrand believed “topography must dictate design. She was a master at reading curves, the sculptural quality of the land, and using plants to highlight those features.” As such, Farrand saw five meadows, divided into rooms by loose hedgerows, interconnected into a necklace. “That’s why we are inexplicably drawn to the next one and the next.” Meadow 5, the final one, is “a broad expanse where I always feel a little lost,” which is perhaps what she wanted us to feel. Weaner echoed these thoughts, adding that “Farrand was sensitive to letting the land express itself.” Like Farrand, “we must follow the place’s natural inclinations,” even with restoring the meadow. “It’s not about what I envision here.”
Since the 1950s, the park has been left to its own devices. The result was the total takeover of the historic design by invasive non-native plants, including Japanese stiltgrass, porcelain berry, wineberry, and others, until the Dumbarton Oaks Park Conservancy started up in earnest a few years ago. Over literally thousands of hours of volunteer labor, the mighty team at the conservancy has turned the tide, enabling Farrand’s design to reappear in many key places. The next phase is recreating the five meadows, all of which had all been overrun except for one.
Meadows are incredibly complex ecosystems and designing them is as much art as science. In a lecture hosted by the George Washington University landscape design program, Weaner said warm season grasses, which are native, are more desirable than cool season grasses, which were imported from Europe, because they sustain the local ecosystem. Cool season grasses mat when they grow, whereas warm season grasses allow for little pockets of life to more easily live amid individual plants. Warm season grasses are natural homes for solitary, non-hive bees and other insects that birds eat. As Doug Tallamy, one of the world’s foremost wildlife ecologists has explained, birds are “insect specific.” Native birds want to eat native bugs, which feed on native plants. If meadows disappear, so do the insects and then the birds. Restoring the native meadows at Dumbarton Oaks Park is then vital to creating the “little rest stops birds need” on their journeys.
Once you’ve intervened in a landscape and you are trying to turn it into a native meadow, you have to work with existing natural processes. Weaner described a meadow as a “system with early and late stage players.” Succession, which is “the changing nature of plants in a place,” is happening at all times. “If we bulldoze a place, we’ll first see small herbaceous grasses, then pioneer shrubs and trees, and then more mature trees.” Trees will eventually push out most of the ground cover, unless they are stopped. But Weaner explained that a sort of micro-succession also occurs within the meadow stage of succession as well. Given some grasses are annual, others are biannual and still others are perennial, “in a one year time period, the dominant species will completely change.”
In a warm season native meadow, perennial plants dominate. “The problem is they establish themselves slowly. They put their energy into root growth as a long-term investment. Perennials are conservative whereas annuals crash and burn. It’s a relay over time.” Given some perennials take up to 7-10 years to flower, and therefore only then create seeds that can restore the ground’s seed bank, “the first 1-3 years are volatile.” Cool season grasses found in meadows 1 and 2 will continue to co-exist alongside new warm season perennials planted in July — Purple Top, Beaked Panicgrass, Side Oats Gamma, and Little Blue Stem — giving the perennials time to get situated and eventually dominate. The idea is the warm season grasses, if supported with mowing each spring, will eventually take over, as the cool season grasses will not be given the opportunity to grow and will eventually die.
Weaner said the conservancy team will need to keep a close watch over the nascent native meadows as any disturbance can easily “push a meadow back to its early stage of succession. Succession can also go backwards.” Invasive plants are a constant threat; they are a “permanent disturbance.” But if invasive can no longer produce new seeds and add to the seed bank, they can be held at bay indefinitely.
Dumbarton Oaks Park, working with nature’s processes, is like a perennial itself, making a long-term investment in the future. More meadows in the necklace will soon be planted with warm season grasses and shepharded. The results of their labors won’t be seen for many years, but the seeds have been planted.