Theory:

     One morning while I was sitting beside Grandfather on the veranda steps, I noticed the tendril of a creeping vine trailing nearby. As we sat there in the soft sunshine of a North Indian winter, I saw the tendril moving slowly towards Grandfather. Twenty minutes later, it had crossed the step and was touching his feet.
 
     There is probably a scientific explanation for the plant’s behavior - something to do with light and warmth perhaps - but I liked to think it moved across the steps simply because it wanted to be near Grandfather. One always felt like drawing close to him. Sometimes when I sat by myself beneath a tree, I would feel rather lonely but as soon as Grandfather joined me, the garden became a happy place. Grandfather had served many years in the Indian Forest Service and it was natural that he should know trees and like them. On his retirement, he built a bungalow on the outskirts of Dehradun, planting trees all around - lime, mango, orange and guava, also eucalyptus, jacaranda, and Persian lilacs. In the fertile Doon Valley, plants and trees grew tall and strong.
Explanation:
 
This story is set in a North Indian city called Dehradun. One day the author was sitting on the balcony steps with his grandfather. He noticed that a slender thread-like stem coming out of a climber plant, from a creeping tree near them. It was early in the morning, and there was soft sunshine, and maybe a light breeze that moved the tendril slowly towards his grandfather. After twenty minutes, it had crossed the balcony steps, and it was touching his feet. The author says North Indian winter in this paragraph. It refers to a pleasant to cold temperature, could be in October to March.
 
vine-4102328_1920.jpg
Tendrils. 
  
The tendrils had moved towards grandfather due to the warm sunshine and some breeze perhaps. But according to the author, he had a different explanation. He felt the plant liked to come near his grandfather and that's why it had moved. He felt his grandfather always drew people towards him. When the author sat below a tree by himself, he always felt lonely; but if his grandfather joined him, he felt the garden became a happier place. He had a reason for it - his grandfather had worked for the Indian Forest Service, and he knew well about trees. After his retirement, he had built a bungalow on the outer parts of Dehradun. He planted many trees around his house - lime, mango, orange, guava, eucalyptus, jacaranda (also known as fern tree), and Persian lilacs. The parts near the Dehradun valley are known for their fertile soil, and the trees looked tall, healthy and strong.
 
jacaranda-322969_1920.jpg
Jacaranda tree. Also seen - eucalyptus tree, lime and other trees around the bungalow.
  
Meanings of difficult words:
  
No.
Words
Meanings
1
verandaa roofed platform along the outside of a house
2
tendrila slender threadlike appendage of a climbing plant, often growing in a spiral form, that stretches out and twines round any suitable support
3
creeping growing along the ground/other surface
4
vine a climbing or trailing woody-stemmed plant related to the grapevine
5
trailing drawn along behind something/someone
6
outskirts outer parts of a city/town
7
fertile capable of producing healthy crops/vegetation
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.