Theory:

Describing words are words used to describe or explain the nature/feature/quality of another word. In English grammar, such words are called adjectives.
Example:
1. My garden has a "beautiful" roses.
In the above sentence, "beautiful" is a word that describes "roses". It tells the feature of the roses.
 
2. My "new" watch broke yesterday.
In the above sentence, "new" is a word that describes the "watch".
 
3. Priya is a "wonderful" dancer.
In the above sentence, "wonderful" is a word that describes the quality of "dancer".
In the poem "Trees", the poet has used many describing words. They are:
 
No.
Describing words
What is described
1
LargestBanyan tree
2
StraightCoconut tree
3
TallCoconut tree
4
SmallNeem tree's fruits
5
PleasantShade of tamarind tree
6
SharpLeaves of dates tree
7
UsefulWood of teak tree
8
GoodFruits of mango tree