It's summertime in Philadelphia, which means you’re bound to come across one of the city's trendy beer gardens on a riverfront or rooftop.  One of the newest additions to the plethora of outdoor watering holes is the 2016 Pennsylvania Horticultural Society Pop-Up Garden at the Viaduct Rail Park.

"We are a destination spot — the epitome of the hidden garden, because you have to seek us out," said Sally Anderson, the pop-up's project manager and owner of Bloom Thyme Design & Gardens.

Tucked beneath the trestle at 10th and Hamilton Streets, the PHS pop-up garden is an amuse-bouche of sorts — to bring attention and buzz to what will become the Reading Viaduct Rail Park.

Friends of the Rail Park, a nonprofit organization, is advocating and fundraising to transform the abandoned viaduct above the pop-up garden into a 3-mile park with walkways, cycling paths, and gathering spaces.

Located in the Callowhill District just north of Center City, the neighborhood is defined by the elevated track of the Philadelphia and Reading Railroad — its rusted frame and overgrown vegetation, and its industrial past.

The temporary garden, which was once a parking lot, features rails cars repurposed into a bar and seating area, plants and greenery inspired by the vegetation on the viaduct, and historic images from the railroad in its heyday.

"PHS pop ups really exist to help people see how horticulture can change the urban environment and create a unique sense of place," said Matt Rader, PHS president. He said the rail park is one of the most exciting transformations of public space that Philadelphia has seen in a long time.

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The elevated tracks of the former Reading Railroad cut across the heart of the Callowhill District and other neighborhoods north of Center City, Philadelphia.  (Lindsay Lazarski/WHYY)

Michael Garden, vice president of Friends of the Rail Park, said the broad reach of PHS and the pop-up garden will bring people to the neighborhood and help them visualize the possibilities for the rail park.

"The temporary garden is the kind of atmosphere that we would like to see at certain locations on the site when it's completed," said Garden.

Garden said he's hoping that phase one of the rail park, a quarter mile stretch between Broad and Callowhill Streets, will break ground before the end of the year — but his organization is still waiting to hear back from the state on grant applications that would secure additional funding for the park.

A diamond in the rough

In Pennsylvania, there are about 400,000 vacant properties according to the 2010 U.S. Census — one tenth of those lots are in Philadelphia.

The PHS pop-up gardens in Philadelphia take up only two of those parcels. PHS, in partnership with the city, manages about 12,000 others as community gardens and passive green spaces.

To transform the parking lot into a pop-up garden, PHS received a grant from The Pew Center for Arts & Heritage for about $360,000 and received other contributions from Arts & Crafts Holdings, the owners of the lot.

Although the pop-up is temporary, Craig Grossman, a partner with Arts & Crafts Holdings, said he's hoping to keep some of the infrastructure to have the lot remain an active green space.

"We think that's what the future looks like here," said Grossman. "We think this will be the building block of something more permanent."

The PHS Pop Up Garden at the Viaduct Rail Park will be open through Sept. 30 from Monday to Thursday, 5 p.m. to 10 p.m., Friday and Saturday, 2 p.m. to midnight, and Sunday, noon to 10 p.m.