Jenna Kendle (Express)

Each year, the U.S. Botanic Garden’s “Season’s Greenings” exhibit transports visitors to a city of magical, miniature buildings, where branches and twigs form windows and roofs are woven from bark. This year’s display, “All Aboard!,” showcases versions of iconic U.S. train stations crafted from more than 70 types of plant materials. There’s also a collection of plant-based re-creations of D.C. landmarks, including the Capitol, the Library of Congress and, new this year, Union Station. The garden collaborates on the models with Applied Imagination, a Kentucky-based company that creates whimsical plant architecture. The goal is to “capture the feeling and overall look of the building,” rather than make an exact replica, says Nick Nelson, a landscape architect at the garden. Here’s a look at the work that went into the Union Station model.

1) Roof

The station’s roof is made from reeds — tall, grasslike plants — and cedar bark, which is durable, flexible and water-resistant. It’s all held together via “a lot of glue,” Nelson says, and the materials are layered in a way that prevents them from popping up and straightening. The team uses table saws to size the bark and other plant materials; for very thin items, floral scissors are often sufficient. It takes 100 to 200 hours to create most models, he says.

2) Windows

All the windows on the building, including the clear arched panes on the roof, are made out of reeds and salt cedar branches. “For a feature like that, it needs to be something that’s very straight and consistent,” Nelson says. “And resin is dripped down over all of it,” which helps the components solidify and adds to the windows’ shiny luster.

3) Railings

The railings on the front of the station are made of magnolia twigs and winged euonymus. The latter, also known as burning bush, “is actually an invasive plant around here,” Nelson says. “It’s a shrub, and it’s used in a lot of buildings around town, typically cut into a hedge. You’ll notice it in the fall because it turns bright red.”

4) Eagles

The birds that adorn four of the station’s columns, anchoring the right and left sides of the building, are made from the flowering stem of sago palm (which only blooms every three to four years), mahogany seed pods and the scales of two types of pine cone: digger and red. The Applied Imagination team works with about 100 pine cone varieties, Nelson says.

5) Statues

The statues of Roman legionnaires atop the station’s center six columns are packed full of materials: cornhusks, tulip poplar seeds, cedrela, sago palm blooms, cinnamon sticks, birch bark, walnut shells, winged euonymus, eucalyptus buds, birch twigs, lafi pods and zinnia flowers. Many of the plant materials used for each model are dehydrated and dried out first, Nelson says. Otherwise, they would “rot and become soft and mushy.”

6) Columns

The stately columns that guard the station are made of mahogany pods, willow twigs, spruce twigs, honeysuckle branches, cinnamon sticks, palm leaves and oak bark. The cinnamon sticks are used to make the curly brown part near the top of each column. “Cinnamon is the outer bark of the cinnamon tree,” Nelson says. “It’s scraped off, and then it curls up, and that’s what gives it the curly look.”

U.S. Botanic Garden, 100 Maryland Ave. SW; through Jan. 1, 10 a.m.-5 p.m., free.