Head stones and photos are not the only way to honor someone's memory.
Over the years, our family has had a number of trees planted in memory of loved ones passed. There's a plum tree blooming on Leavenworth in San Francisco with a placque in memory of my Aunt Lenore. Along Rolla's Acorn Trail, an oak tree was added in memory of a fellow City Councilmember who died while in office.
In my one-acre hillside garden, a number of plants bring back memories of loved ones; iris for my Mom, who had lovely iris flower beds in our farmhouse in southern Illinois. Miniature fruit trees among flower beds are in memory of my father, descendant from a long line of Hungarian farmers. He also added a fruit orchard on our southern Illinois property but I don't recall picking much fruit.
To some, visiting a grave is a way to honor those no longer with us. All I have to do is walk into my garden.
Mom, I miss you.