The slate roof was deteriorating on the springhouse at the Lehigh Gap Nature Center. Liz Stauffer, a gardener and caretaker at the Center, thought it was a good opportunity to try something different. She suggested creating a green roof.

Trusses had to be replaced and the roof strengthened. On top of that was a rubber liner protected by a tarp, and carpet to hold moisture and permit it to percolate.

The area was divided into approximately two-foot-square bracings to hold the Rooflite, a certified green-roof medium. It consists of small pebbles, fine matter and 10 percent compost which will break down over time. It drains well to prevent waterlogging.

Native plants were chosen with those that were better suited for wetland placed near the bottom of the roof. Stauffer said there was disagreement whether it could all be done with native plants but she said they just had to choose what suits the conditions. She sees no problem.

The boxes were filled and on May 4 planting was done. The roots will hold the soil when the plants are established.

Gutters will be filled with riverstone to cover the liner and keep it looking nice.

"It's an exciting opportunity to do something different," said Stauffer.

At the end of the planting it looked sparsely vegetated but the plants will spread and some that were unavailable at the time will be added.