Theory:

     Some years later, I returned to Dehradun. After first visiting the old house – it hadn’t changed much – I walked out of town towards the river-bed. It was February. As I looked across the dry water-course, my eye was immediately caught by the spectacular red blooms of the coral blossom. In contrast with the dry river-bed, the island was a small green paradise. When I went up to the trees, I noticed that some squirrels were living in them and a koel, a crow pheasant, challenged me with a mellow ‘who-are-you, who-are-you.’
 
     But the trees seemed to know me; they whispered among themselves and beckoned me nearer. And looking around I noticed that other smaller trees, wild plants and grasses had sprung up under their protection. Yes, the trees we had planted long ago had multiplied. They were walking again. In one small corner of the world, Grandfather’s dream had come true.
Explanation:
 
After some years the author returned to Dehradun. He visited the old house, and it had looked almost the same. He walked to the outskirts to the riverbed. It was the month of February. He saw the dry riverbed, and he immediately saw the striking red flowers of the coral blossom.
 
coral.jpg
Spectacular coral-red blooms!
  
The river-bed was dry, but in contrast, the island looked like a small green paradise. He walked up to the trees and noticed that some squirrels, a koel, crow pheasant were living in the tree. It seemed to him like they were all asking him who he was, in a soft, smooth voice.
 
paradise.jpg
The island looked like a small green paradise!
 
The author felt the trees knew him. They seemed to murmur amongst themselves and signalled him to come closer to them. He also noticed that there were other smaller trees, wild plants, and grass had emerged out under the shelter of the trees. The trees planted long back had increased in number. They seemed to be walking again. The author realized that his grandfather's dream had come true.
 
Meanings of difficult words:
 
No.
Words
Meanings
1
spectacularbeautiful in a dramatic and eye-catching way
2
whisperedspeak very softly
3
beckonedto signal (someone) with your hand to ask the person to come closer or follow
4
sprungappear unexpectedly from
5
mellowpleasant, soft, smooth tone
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-6. When the Trees Walked - Ruskin Bond (pp. 107-122). Published by the Tamil Nadu Textbook and Educational Services Corporation.