An Eliot-based landscaping company that has competed with a neighboring firm for nearly four decades has now bought out its rival. Piscataqua Landscaping & Tree Service has acquired Jacqueline Nooney Landscape Inc. for an undisclosed price, according to a news release. With about a dozen employees from Nooney joining Piscataqua, the company expects its workforce to total nearly 150, spokesman Jamie Storrs told Mainebiz Wednesday. Jacquelyn Nooney is a Yale University art school graduate who moved to Maine in 1982, and founded the landscaping firm two years later. In a letter to clients, she said she is retiring and called Piscataqua “the one company in the region that can continue to provide the high-quality service [my clients] are accustomed to.”