Ice
Ice
Gem.
Gem, perhaps?
tree
One possibility is the word diamond. Diamonds are the hardest substance in the world.
Maple.
tree
ElmOak
There isn't one that begins with an 'S' A three letter word for an evergreen tree is fir.
pine
Tree
The main stem of a tree is the 4-letter word bole. The word is a noun and is another word for truck.