Walking through a park, I passed a massive oak tree. A vine had grown up along its trunk. The vine started small - nothing to bother about. But over the years the vine had gotten taller and taller. By the time I passed, the entire lower half of the tree was covered by the vine's creepers. The mass of tiny feelers was so thick that the tree looked as though it had innumerable birds' nests in it.
Now the tree was in danger. This huge, solid oak was quite literally being taken over; the life was being squeezed from it. But the gardeners in that park had seen the danger.