The term 'Trees of the Myrtle Family' refers to a group of trees that are part of the Myrtaceae family. This family includes guavas, which is a 6-letter word that can be used to solve the crossword. Guavas are tropical fruits that are native to Central and South America, but are now grown in many other parts of the world. They have a sweet flavor and are often eaten raw or used to make jams and jellies.