An antenna, topped with a white hemisphere, emerges from Deven Azevedo's backpack.

Azevedo and Amy Patterson, both Langley high school students, are trekking through parks and public paths around Langley City looking for weeds.

As summer stu-dents with the Langley Environmental Partners Society (LEPS) they're charting invasive species in City parks using a high-sensitivity GPS device.

Patterson and Azevedo are half of the Managing the Environment and Stewarding Habitat (MESH) program this summer.

Until the last day of August, they'll keep working on a detailed map of what types of invasive species are in Langley City.

At the spot they were mapping recently, near 200th Street and 46A Avenue under the BC Hydro transmission towers, they found a lot of plants to note down.

Azevedo and Patterson circled a clump of knotweed at least 20 feet long and almost as wide. Mixed in with the knotweed - which can break through concrete and asphalt - they found Himalayan blackberry and common tansy. Scattered through the rest of the right of way are more weeds and Scotch broom, the ubiquitous plant whose bright yellow flowers announce its presence every spring.

None of the plants are native to B.C. Most can be invasive and destructive to native species.

The students were excited after hearing about the project at their schools.

"I was pretty stoked," said Langley Fundamental Secondary student Patterson.

After LEPS came to her school, she attended a meeting and signed up.

As for Azevedo, the Langley Fine Arts student is one of the Langley Environmental Hero award winners, and heard about the mapping project via the LEPS newsletter.

The map they and the other students create will be heading to the City early this fall.

"Later, we can plan our plan of attack," said Lisa Dreves of LEPS.

She's overseeing the students this summer and teaching them about the GPS device.

It's the same kit that LEPS has used for its past projects of mapping streams around the community.

Keeping track of, and sometimes removing, invasive species has been a long-term goal of LEPS.

In the past, Dreves has warned about giant hogweed, a highly toxic plant that can grow more than a dozen feet tall, and the sap from which can cause chemical burns.

She's also watching out for knotweed, after reports that it has been seen near the footings of the Ironworkers Memorial Brige, causing fears it could actually damage the foundations.

Hopefully, the City will look into removing some of the plants, but in other cases it will have to control the plants to keep them from getting out of hand. Some areas simply can't be completely free of the invasive species.

mclaxton@langleyadvance.com