Theory:

It takes much time to kill a tree,
Not a simple jab of the knife
Will do it. It has grown
Slowly consuming the earth,
Rising out of it, feeding
Upon its crust, absorbing
Years of sunlight, air, water,
And out of its leprous hide
Sprouting leaves.
 
So hack and chop
But this alone won’t do it.
Not so much pain will do it.
The bleeding bark will heal
And from close to the ground
Will rise curled green twigs,
Miniature boughs
Which if unchecked will expand again
To former size.
Explanation:
  
The poet says it takes a lot of time to cut a tree. It is not an easy job. A simple rough poke with a knife may not be enough to cut it down.
 
jab knife.jpg
A simple jab of the knife cannot kill a tree!
  
It takes a lot of effort to kill a tree because it has grown after a long process. It has slowly fed upon the earth's soil filled with nutrients. It has gradually emerged out of the ground after consuming the hardened layer of the soil. It has been drawing in sunlight, air, and water over several years for it to flourish. The tree has spread out its flourishing leaves out of its rough, scaly skin. Like how a man grows for years after consuming nutritious food, breathing air, drinking water, the tree also has grown similarly. The poet has personified the tree as a person in this context.
 
scaly tree.jpg
Sprouting leaves emerging from the leprous hide of the tree!
  
If a simple jab is not enough, the next step is to use more force to cut the tree down. So the tree has to be cut by giving powerful punches and blows; it is repeatedly cut into pieces - but still the job is not done. Even if we apply this much efforts and pains, the tree will not die. The poet says the "bleeding bark" - he does not refer to the actual blood bleeding from the tree (like for a human). He means the sap or the fluid in a tree, which oozes out when a tree is cut down. He compares the sap to the human blood here, by drawing the reference of "bleeding bark".
 
bleeding tree.jpg
Sap bleeding from a cut tree.
  
The poet says even the bleeding bark will heal itself. It will rise again from near the ground with small green spiral stick-like branches. Slowly the main branch of the tree will also sprout out. If man does not continue with his cutting activity, soon it will regrow to its original size.
 
sprout from a tree.jpg
New life from a cut tree!
  
Meanings of difficult words:
  
No.
Words
Meanings
1
jabpoke roughly or quickly, especially with something sharp or pointed
2
crusta hardened layer, coating, or deposit on the surface of something soft
3
leprousrelating to a skin disease caused by infection, where the skin appears scaly
4
hidea thick, strong skin used to conceal oneself
5
hackcut with rough or heavy blows
6
chopcut (something) into pieces with repeated sharp blows of an axe or knife
7
miniaturevery small of its kind
8
boughsa main branch of a tree
Reference:
State Council of Educational Research and Training (2019). Term-2 English Standard-9. On Killing a Tree - Dr. Gieve Patel (pp. 146-152). Published by the Tamil Nadu Textbook and Educational Services Corporation.