Using some outside the flower-box thinking, the Phipps Conservatory and Botanical Gardens will be ripping out half of its front lawn in Oakland this week in order to build a parking lot.

The lot will be a "green" one, however, using recycled plastic materials designed by Alcoa Geosystems that allow grass to keep growing, even as vehicles park atop it.

One of the region's leading environmental institutions, the Carnegie Museums of Pittsburgh's Powdermill Nature Reserve in Westmoreland County, has used a similar green parking system.

Phipps is making the move in advance of the May 10 opening of its Dale Chihuly glass exhibition, which is expected to be the biggest-drawing artistic event of the year. An estimated 300,000 people are expected to visit Phipps through the exhibition's November closing, more than 30 percent of them from outside the region.

Mr. Chihuly is the nation's best-known glass artist and his shows at other botanical gardens similar to Phipps have been major events: Last year's show at the Missouri Botanical Garden drew 350,000 people and triggered a 25 percent increase in membership, said the St. Louis garden's special events manager, Lynn Kerkemeyer.

Phipps has little parking infrastructure for such crowds -- only a couple of dozen dedicated spaces in a parking island on Schenley Drive -- leading to the decision to add the green lot, which will hold roughly 100 vehicles.

Workers are set to tear up the sloping lawn to the right of Phipps' entrance this week and will lay the plastic "Geoblock" system the week of April 16, when tickets to the Chihuly exhibit go on sale. The new lot will not be available for parking until mid-July, since about three months are required for the grass to re-root.

Alcoa is donating 25 percent of the Geoblock product to Phipps. Though the "permeable parking" technology, which looks like a system of black plastic egg cartons, has been used widely for two decades, it is the first time Alcoa officials can recall installing it in Pittsburgh.

Though the lot will be permanent, the Phipps plan is to use it only when necessary for overflow parking. Lines will not be painted on the grass, so the hope is when no cars are parked there the entrance area will still appear to be a sloping grassy hill.

Phipps officials are also talking to the Pittsburgh Parking Authority about changing existing parking and traffic patterns along Schenley Drive to accommodate more visitors.

Additional information on Oakland parking choices, such as the garage under Soldiers & Sailors National Military Museum & Memorial, will be attached to Chihuly tickets.

Phipps already is bidding to become one of the most environmentally-friendly conservatories in the world. Its new Tropical Forest wing absorbs heat in the winter and is cooled by earth tubes and fabric screens in the summer.

It is the first conservatory to use a fuel cell -- manufactured by Pittsburgh-based Siemens Power Generation -- that cleanly produces energy from natural gas.