Harvard University has bought 52 acres in Allston during the past nine years in a secret buying spree that increases the school's land in Boston by more than a third.

Working through the Beal Cos., a prominent real estate development company, Harvard spent $88 million to buy 14 separate parcels in the area near its Graduate School of Business as they became available.

Harvard officials said the university made the purchases without revealing its identity to the sellers, residents, local politicians, or city officials because property owners would have drastically inflated the prices if they knew Harvard was the buyer.