She succeeds Lorraine Dunk, who is now director of the International Tree Foundation.
Friend was previously deputy director at the Farnham Maltings Arts & Community Centre. She has particular expertise in community participation and fundraising, and has worked as the Landscape Institute's head of policy.
Friend said: "As a charity, the trust is in a unique position to work across professional, cultural and political boundaries and promote the potential of landscape to improve the quality of our lives. I am looking forward to building on LDT's relationships with CABE Space, Groundwork and Natural England, and creating new alliances with the landscape professions as well as organisations concerned with our health, culture and heritage."
LDT board chairman Liz Lake added: "Friend's enthusiasm and combination of skills and experience are exactly what the trust needs to take us forward."