A group of trees is called a wood
from which a forest area could be called a woodland.
Palm trees
A narrow valley with 4 letters is called a "rift."
The third group of Paul's letters contains four epistles: Ephesians, Colossians, Philippians, and Philemon.
bloc
Dove or Crow
Isle
Sire
Pixie - which is actually 5 letters.
trio
Quartet.
A group of five is called a "Quintet".
a small group