Forestiere began building the underground arboretum in 1906 when he bought land near Fresno that he thought was fertile, but soon discovered it was hardpan. Seeking to escape the scorching heat of the San Joaquin Valley, he was inspired to seek refuge underground, where he found that the soil was actually fertile for growing plants. Over the course of the next 40 years until his death, he carefully carved 10,000 square feet of subterranean bedrooms, living rooms, a kitchen, a chapel, a fish pond, and a network of gardens, trees and trellises all by hand- and without architectural training.
The underground caverns are supported by Roman arches, columns, and domes. Forestiere capped many of the domes with grated skylights that let light in to the living areas and gardens below. Forestiere planted a variety of trees 10 to 25 feet below the earth’s surface – their tops poke through the skylights, offering fruit to passersby. The underground garden is rich with Almond, Pomegranate, Pear, Olive, Persimmon, Avocado, Loquat, Quince, Carob, Jujube, Arbutus, Black Fig, Tangerine, Grapefruit, Orange, Kumquat, Lemon, Date Palm and Mulbery trees. Forestiere, the son of a citrus farmer, even grafted one tree to produce seven varieties of citrus fruit!
Growing underground, the trees and plants are protected from hot weather in the summer, frost in the winter, and animals and insects all year-round. The trees are watered with rainwater collected in large bins. Wine grapes dangle from overhead trellises, also reachable from the surface.
Forestiere, who could not read or write in English, created the idyllic garden by himself, using only his experience as a Boston subway digger, and gardening knowledge from his upbringing to create his own personal Garden of Eden. The gardens are maintained to this day by Baldasare’s nephew Ric and his family members.