Ann Grube lived two blocks down the street from her current Hinsdale home for seven years, in a house whose garden faced north. It wasn't a happy situation, she says: "In this climate, north doesn't work." Casing the neighborhood for southern exposures, she came upon a big English garden behind a 1926 Tudor home designed by Chicago architect Benjamin Marshall. The original owner, an Anglophile, had put in traditional brick walls and a sunken area graced by a waterfall, a key-shaped pool, and a cast-iron fountain. "It was perfect," says Grube. Or rather, it had been, and could be again. She and her husband, John, have been working on it since they bought the property 13 years ago. With the help of landscape architect Craig Bergmann, they began by digging up most of the yard-two and a half feet deep-and replacing the claylike dirt with good black soil. Grube says the swimming pool they added last year-approached through arches of roses, surrounded by a white garden, and screened from the house by flowering pear espaliers-should be the last major project. Landscaping in front of the house is understated: red impatiens, boxwoods, red maples, and a few precious elms. That's deliberate, Grube says, so that when you get to the backyard, you go, "Whoa!" This Saturday, July 24, the Grubes are one of a half-dozen families in Hinsdale, La Grange, and Oak Brook making their private bits of paradise available to all as part of the Garden Conservancy's Open Days program. Between 10 AM and 4 PM, visitors can buy a directory with addresses and directions and begin a tour of the gardens (in their own cars) at 942 N. Madison in Hinsdale or 3711 Madison in Oak Brook. The directory is $5; admission is $5 at each garden. Proceeds support the Garden Conservancy (a national nonprofit whose mission is "to preserve exceptional gardens and open them to the public") and local charities. Call 888-842-2442 for more information.