For being such a concrete metropolis, Washington, D.C., is green.

There are nearly 77,000 acres of parks in the region, making it one of the lushest urban cities in America — and most people may not even realize what they have in their backyard. That’s something the organizers of National Public Lands Day, taking place this Saturday, hope to

change, said NPLD Program Director Robb Hampton.

Take, for example, Kenilworth Aquatic Gardens. It’s “an oasis of Washington, D.C.,” Hampton said of the “signature site” for the nationwide service day. “You get there and you can’t believe you’re in Northeast D.C.”

The park, located on 12 acres along the east bank of the Anacostia River, boasts 35 ponds and an estuary and is the only national park devoted entirely to aquatic-loving plants. The problem is, wild bamboo and water lilies are growing out of control.

That’s where Public Lands Day comes in. The 14th annual event isn’t just about public awareness, it’s about helping maintain those sites so the community can use them for years to come; it’s about teaching children how to both enrich and enjoy nature.

NPLD began in 1994 with three federal agencies and 700 volunteers in the name of restoring the legacy of the Civilian Conservation Corps, the 3-million-strong “tree army” that worked to preserve and improve public lands during the Great Depression. This year, 110,000 volunteers are expected at 1,300 sites nationwide with nine federal agencies, retail sponsorship and countless nonprofits involved.

According to the National Environmental Education Foundation, NPLD has grown into the largest volunteer hands-on activity of its kind.

From coast-to-coast, volunteers will create and clear trails, repair bridges and historic structures, pick up trash, monitor endangered species and restore habitats.

And with that many hands on board not only can a lot get accomplished but also a lot of money can be saved. The Bureau of Labor Statistics estimates the value of volunteer time is $18.77 an hour, which means with 110,000 volunteers in just one hour more than $2 million can be banked.

Greenbelt Park only has one person on staff who works on clearing the trails throughout the year, REI Outreach Specialist Barbara Ball said, and “that’s why REI tries to help out and rally support whenever they can.” The store’s College Park, Md., location, which is just down the road from the park, has had a relationship with the facility for years. “We like to hook up with national and state parks to promote the system to the public,” she said. “If we don’t keep green places green, there will be nowhere to go.”

This year, one of the major focuses of NPLD is to stop the tide of invasive plants that are taking over and destroying natural environments.

“Foreign fauna,” Hampton said, “can strangle out other native vegetation.”

He said it is mainly weeds as well as ornamental plants that people use to landscape their yards, and with wind and pollination the plants spread and can “throw off entire habit species.”

Beyond the lily pads (weeds) and bamboo (neighbors’ drifting landscape) at Kenilworth Aquatic Gardens, Hampton said the National Capital Region is being bombarded with honey suckle and garlic mustard plants.

And other regions have their own deep-rooted demons, like kudzu in the Southeast, and ever since Hurricane Katrina, Chinese tallow ornamental trees have sprung up unwanted all over the New Orleans landscape.

Here’s a sample of what’s being done locally for NPLD. (For a complete list of locations, visit publiclandsday.org.) The National Park Service will provide any needed equipment, so don’t feel like you need to dig through the garage for your galoshes or gardening gloves, but do make sure to wear long pants, long sleeves and no open-toe shoes as there are poison ivy, thorns and ticks at some sites.

The weather is expected to be a mix of sunshine and cool breezes on Saturday, the perfect climate in which to explore that gem in your backyard and help it remain there for years to come.

Kenilworth Aquatic Gardens

One of the main missions Saturday at the Aquatic Gardens (1550 Anacostia Ave. NE; 202-426-6905) is to cut back invasive plants such as lotus leaves and remove bamboo and vines along the boardwalk that are “taking over,” Hampton said.

More than 200 people are expected to come out to the Northeast site, said Alan Spears, legislative representative for the National Parks Conservation Association and event organizer.

Beyond pulling those pesky intruders, there are 10 different projects, also including land and water litter cleanup (if you want to have some fun, canoes and pontoon boats will be provided for this) as well as building benches, putting up new signs, creating flower beds and pruning trees. And, while you are there, it is a wonderful opportunity to view a rare breed of white lilies imported years ago by garden founder W.B. Shaw from his home in Maine to what was then an abandoned ice pond in Washington.

Walk-on volunteers are welcome, Spears said, but it helps to RSVP so it is ensured there will be enough equipment available as well as food, as complimentary breakfast and lunch will be provided by Toyota and NEEF. To sign up or for more information, contact Spears at 202-454-3384.

Greenbelt Park

At Greenbelt Park (6565 Greenbelt Road, Greenbelt, Md.; 301-344-3948), there will be a variety of projects as well, “because we wanted everyone of all ages and abilities to participate,” Ball said. “We wanted the kids to come along with their parents.”

The focus in Prince George’s this weekend will be on cleaning up the Still Creek watershed, which flows through the park and eventually into the Anacostia River, Potomac River and the Chesapeake Bay, and clearing the paths on several of the park’s trails. And if you’re looking for some hard labor, there’ll be some of that, too, including rerouting some trails and laying waterbars to keep water off trails, Ball said.

As snacks and water will be provided, participants should pre-register with REI, who is helping organize the event, by calling 301-982-9681.

Carderock

That’s land and water covered, but what about air? That’s where The Access Fund’s Adopt-a-Crag comes in, sort of.

The Carderock event is catered — literally, there is a barbecue following — to rock climbers. Part of C&O Canal National Historical Park, in Montgomery County, Md., off Clara Barton Parkway, the “crag” is in need of cliff cleanup, erosion control work and trail reinforcement.

But, event organizer Thompson Ling said, there are activities suitable for “ages 7 to 60.”

The trails at the top and bottom of the cliff suffer from soil compaction, which can kill the trees, said Ling, The Access Fund’s regional coordinator for Maryland, so a good amount of mulch needs to be laid.

The Access Fund partners with NPLD and this year also is teaming with the Navy, which is sending volunteers to help with the efforts. Ling is expecting at least 100 volunteers on Saturday, which marks the event’s third year at Carderock.

“This is a great demonstration of how recreation and conservation can work together in education,” he said. We are “dedicated to preserving cliff areas and making sure they stay open.”

T-shirts and the barbecue are free; just make sure to register at dcmetroclimbing.com, or e-mail adoptacrag@dcmetroclimbing.com.