I once decided that hedges can be quite boring, green leaves, growing tight together and really nothing special. I decided to plant some sweet pea seeds to give them a little colour. That was about 12 years ago. My hedges are still there and so are the sweet pea plants. Sweet peas climb and attach themselves with their wiry fingers to anything. They also produce seeds.
The result of my effort is that I have sweet peas springing up everywhere in my hedges and the seeds decided to wander to a few other places. The area around my garden now has them everywhere. Opposite there is a small plot of land with a few bushes, even a tree which the local gardener cares for. He was once there removing the sweet peas in Summer and I told him they were probably from the seeds produced by my plants. He laughed and said he had suspicions that it was something like that, but he never really removed them, I do not think he could. He just cuts them back once a year. They are also growing in our wild meadow opposite. My neighbour has even ensured that they remain after the meadow is cut once a year. Yes, we love our sweet peas.