| Grass or weeds will still grow between the cracks with sand but mortar will not help much because some weeds grow on very little soil. You may want to check out creeping low growing perennials that may fill in the areas between the cracks and keep things from shifting. Perennials.com is a good place to start. I am not in your zone so I won't dare recommend anything. |
Here is a link that might be useful: Propagating Perennials