I have visited Sissinghurst castle garden a few times and on my last visit picked up this book, it is very interesting and has some great insights into the countryside.
Adam's father taught him a lot about the countryside, here is an excerpt from the book.
As children we were always taught that you must try to sympathise with the spiky and the spiny, to understand what it was that did not allow them to open, displaying elegance of the beech or the confidence of the oak. Why are thorns so bitter? What can be the point, in such a calm English wood, of such unfriendliness? You feel like asking them to relax, even if the relaxation is not in their nature. But everywhere in the woods at Sissinghurst there is one repeated clue to this foundation-level exercise in tree psychology.
At the foot of almost every oak there is at least one holy nestling in the shade. Why? Why is the spiky holly drawn to the oak? What sort of symbiosis is this? But the question, it turns out, may be the wrong way round.
Why does the oak live with the holly? Because the holly, when they were both young looked after the oak. Its spiky evergreen leaves protected the young acorn seedling from the browsing lips of the ever-hungry deer. The oak had a holly nurse, and only after a while did the young tree outstrip the protector that now shelters in the shade.
I am looking forward to learning more.