Saps
pine
bole
tree
Tree.
The main stem of a tree is the 4-letter word bole. The word is a noun and is another word for truck.
tree
Then, They, Than, Tear, Torn, Tree, Tire, Tame, Tent
pick
seed
The letters do not spell any 5 letter word. They can be used to spell the 4 letter words firs (an evergreen tree), fish and rifs (to dismiss from employment).
bean
Envy Is A 4-Letter Word