Posted: 28/04/2013 at 18:05
If the plants in question are on your own property then you may dig them up. However as you say they are tucked away in a wall then seed is the best option. Keep your eye on the plants and collect the seed when it seperates easily from the seed pod. Sow straight away in ordinary cojpost, put somewhere shay and keep moist. Do not bury the seed, it is best surface sown. It should berminate the following Spring.
Or just throw the seed on the soil at the base of the wall and let nature take its cours.