Buying a piece of the garden at its biggest wingding of the year.

Visitors to the South Coast Botanic Garden on the Palos Verdes Peninsula are usually asked to enjoy the greenery and colorful flowers, but to leave them where they are.

On Saturday and Sunday, however, you can take the plants home--provided you pay for them first and remove only the ones that are for sale.

And even the most finicky gardener is bound to find something of interest, because 10,000 plants will be available during “Fiesta de Flores,” the annual fund-raiser for the 87-acre garden--one of the first in the world planted on a sanitary landfill, beginning in 1961.

According to Norma Cantafio, executive director of the garden’s volunteer foundation, which is putting on the sale, the purchase price will be right--averaging between $1.50 and $16.

And what should prove most popular?

Roses, fruit trees, fuchsias and a variety of cacti, Cantafio said. “Our meadow is loaded with plants.”

Nearly every weekend, the garden has some special program, but the fiesta--which comes complete with band concerts, displays and demonstrations, crafts, food and tours--is its biggest wingding of the year, attracting about 5,000 people. (Foundation members and guests will have a preview party Friday from 4 to 8 p.m. at $10 a person.)

This week, garden volunteers have been busy setting up tents, pricing plants--most of them grown at the garden--and putting them out on the meadow. Jo Bright of Rancho Palos Verdes is working her fifth fiesta.

“I love gardening and this is so close to my home,” she said, adding that her favorite place to work is the propagation center where plants are grown from seedlings or cuttings.

It’s the first fiesta for Tina Arnold, another volunteer who also lives in Rancho Palos Verdes. “I’m interested in gardening and have been taking classes for several years and this is a good chance to get involved,” she said.

The fiesta underscores the importance of the foundation, which Tak Niiya--the ranking county Department of Arboreta and Botanic Gardens staffer at the garden--regards as the backbone of the place. The foundation’s 2,400 members provide money and volunteer time doing such things as running the gift shop, conducting crafts workshops and docent tours, and giving lectures and classes.

A large section of the garden is created by volunteers, where they grow vegetables and flowers and maintain a rose garden. “We believe in the garden and we want to make it a lovely place for the community and visitors from out of state,” Cantafio said.

During its 27 years, the garden has never escaped its origins as a dump and, prior to that, a mine for diatomaceous earth. Composed of the fossil remains of one-celled algae called diatoms, it is used for filtration. But the light and porous diatomaceous soil is poor for growing because it inhibits root growth and must be fertilized regularly. Tall trees cannot be grown because they would topple.

The settling of refuse has caused land subsidence, which puts waves in the garden’s parking lots and roads and requires frequent hole-filling. And the decomposing organic matter buried below the garden produces gases that must be piped off.

To grow a garden under such conditions, “we have to try harder,” Niiya said.

The challenges, however, have also drawn the eyes of the horticultural world to the Peninsula garden as a daily example of how a trash heap can be transformed into something beautiful.

Open every day except Christmas, the garden draws 100,000 visitors a year, offering them more than 150,000 plants representing 2,000 different species. It is particularly rich in hearty, drought-resistant vegetation of Australia and South Africa, which have climates similar to the Peninsula’s.

Last year, the garden felt a need to refurbish and has hired an architectural and planning organization to develop a long-term master plan. Some of the $60,000 expected from “Fiesta de Flores” will be used for the project.