Leaves On, Leaves Off: Capitol Grounds Works Through the Winter

"Even when the neighborhood isn't as lively, we have plenty to do," affirms Jim Kaufmann, Director of Capitol Grounds and Arboretum.

From November to March, Kaufmann's team of 80 takes on recurring to-dos: tree health checks, bulb planting and staff training sessions. In addition, they routinely study the forecast and brace for whatever weather comes their way. Over the years, the team's earned a reputation for setting the standard of winter preparedness in the city. This winter, the Capitol Grounds experts were equipped with 800 tons of bulk rock salt, 1,500 gallons of liquid pretreat product, 18 plow trucks — and more.

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Road Technology

Already in 2024, the region has seen more snowfall than the previous two years combined, supporting Farmers' Almanac predictions. In the last month, low-temperature winter storms brought several inches of precipitation. Some locals woke up surprised by the glistening blanket of snow — but Kaufmann and his team had been prepared for days.

The Capitol Grounds team studies several versions of local forecasts from third-party providers, comparing and contrasting each with their own data. Their data stems from the use of a groundbreaking (or, should we say, ground clearing) device, the Mobile Advanced Road Weather Information Center (MARWIS). MARWIS collects in-depth analytics on ground wetness, ground temperature, dew point, and the presence of ice, snow or slush. Before a storm is expected to hit, Kaufmann attaches the MARWIS equipment to the side of a Capitol Grounds pickup truck. While he drives, the device takes measurements and photos that can be examined on its screen in real-time, or hours later on a laptop.

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A MARWIS snapshot displays local weather patterns and takes pictures.

By traversing the perimeter of the Capitol campus and its surrounding neighborhoods with MARWIS, Kaufmann effectively creates a hyperlocal weather forecast. By identifying the potential wettest or iciest areas — down to a single street corner or intersection — he and his team can allocate resources like salt and shovelers in advance of the storm system’s arrival. In the seasons since he and the team began using MARWIS, Kaufmann has picked up on a few trends.  

"We usually see the weather 'split' along the I-95 corridor," he says. "It might rain on the east side of the highway while it's perfectly dry on the west."

"Locally, on campus, we see quicker icing conditions on the East Plaza of the U.S. Capitol than the rest of the paved surfaces," he continued. "There are definite microclimates ranging between the north and south side of campus as well as between the north and south facing sides of buildings."

After the storm has passed, Kaufmann uses MARWIS readings to measure and mitigate any damage from flooding, blockages or remaining ice. Together, the team ensures areas have returned to their normal conditions — baselines they established months prior in partnership with entities like D.C. Public Works. Since August 2023, Capitol Grounds and D.C. Public Works have met regularly to establish best practices and storm protocols that protect and inform the Capitol Hill community.

An AOC snowplow clears a pile of January 2024 snow; Early morning snowfall at the U.S. Capitol.

MARWIS is just one representation of the advanced technologies Capitol Grounds uses to pursue its mission alongside the rest of the AOC. Local and national trade shows — which often take place during colder months — exhibit agricultural and horticultural equipment on the forefront of today's groundskeeping needs. Kaufmann says these shows allow him to evaluate possible additions to the Capitol Grounds fleet. At present, he's focused on finding sustainable equipment like commercial mowers and other grounds equipment that's less gas-reliant than machines of previous generations.

Check-Up Season

Tree "check-ups" are another important element in Capitol Grounds' conservation efforts.

"In the winter months, we can learn a lot about the health of campus horticulture," Kaufmann remarks. "We rotate our tree inspections — one with leaves on, the next with leaves off — to see how each is faring."

"Leaf-off" season is more indicative of structural issues: it's easier to identify limb defects, decay or damage caused by invasive species. Intentional pruning of specific species also promotes proper pruning cycles while reducing susceptibility to biotic stressors.

Capitol Grounds using a grinding machine to remove dead tree roots; conducting structural pruning.

In tandem with the trimming, Capitol Grounds spends winter preparing the planting beds on Capitol Square in accordance with Frederick Law Olmsted's plans — which form a 150-year-old tradition of caring for the campus.

Dead trees are removed and replaced, at seasonally appropriate times, with saplings. On average, Capitol Grounds arborists plant more than 100 trees across campus every year. Special projects arise, too, bringing this year's total a bit higher: one landscape renovation brought 15 deciduous tree species — including dogwood (cornus x rutcan 'constellation') and magnolia 'sargents' (magnolia sargentiana) — to the area around the Russell Senate Office Building. Forty other various trees were also planted in the recently restored Capitol Visitor Center entrance landscape.  

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A small Senate Parks resident awaits the arrival of spring.

When planting, Capitol Grounds considers sustainable approaches to the protective groundcovers that allow saplings to adapt and grow. The team has increased its use of "no-mow" turf, a blanket of grass that uses less water and fertilizer than traditional turfgrass. As the name suggests, these areas won't be mowed, either. Kaufmann is particularly excited for the no-mow method to be exhibited in such a public and highly visible space. He hopes visitors can appreciate the many green methods his team employs around D.C.'s most recognizable landmarks.

Preparing Well

Even with their jobs' lengthy checklist, Capitol Grounds arborists make time to participate in their own sort of check-ups through specialized trainings that use mock scenarios. These sessions ensure every individual can competently execute emergency procedures and operate the necessary equipment: crucial skills for professionals working with large tools and plantings across a large space.

An overall team training favorite is the annual high angle rescue exercise. The weeklong activity is set up in late winter or early spring in the Senate Parks and requires participants to "save" a rescue dummy or Capitol Grounds arborist from a tree. The person or prop is placed as if they had been rendered incapacitated while working in high branches. Each trainee must ascend the tree and decide how best to remove the person, clipping into their harness and avoiding electrical wires or equipment, before transporting them to the ground.

"It's almost as if you create a makeshift zipline to get over hazards and make a safe descent," Kaufmann says. "It's a pretty popular training — we often invite folks from other jurisdictions to come watch."

His team's enthusiasm in every aspect of their work, no matter the season, pays off.

Come rain or shine, the AOC's Capitol Grounds is determined to keep Capitol Hill the picturesque site millions visit every year.