The phrase "in leaf" refers to the state of a tree or plant when it has grown new leaves. It signifies the onset of spring and serves as a symbol of new beginnings. Some synonyms for "in leaf" include "foliated," "leafy," and "flushed with foliage." These words evoke images of a lush garden or forest, filled with vibrant greenery. Other synonyms that can be used in this context include "frondescent," "verdant," and "buoyant with life." The use of synonyms can help to add variety to one's writing and make it more engaging and descriptive.