Thanks again for your quick response. I am resending the images by splitting them into 3 separate questions to make it easier to see the images.
1. On the side of my house that is south facing, there are many little trees that are sprouting between the pavers and on stones. My husband cut them down last year, but they just branch off and regrow again. This year, I pulled out what I could and cut down what I couldn’t pull up. If I keep cutting it down year after year will it eventually die? I have young kids so I’m hoping for a more natural and safe solution. I have heard mixed things about using vinegar, salt, and boiling water. I don’t plan on planting anything in this area since it is the side of my house. So as long as the solution works and is child-safe, I am happy with it. I know the best option would be the remove all the stones, dig-out the area, but I am hoping for a less labour intensive option.
Without foliage, it is not possible to make a positive identification of these tree seedlings. To my eye they look very much like Ailanthus altissima, Tree of Heaven, in the way they have emerged with no branching and no discernible buds. By now, if they were maples, you should be able to see the first small leaves unfurling with their unmistakable shape. Like maples, Tree of Heaven is a prolific self-seeder, each mature tree producing thousands of samaras, or keys, which can easily find their way between pavers. Invasive trees and shrubs are particularly adept at establishing themselves quickly, both above and below ground, with their roots growing and spreading efficiently. Have you looked at the mature trees around your neighbours’ gardens? If these are tree seedlings, they have likely been distributed by wind.
The Toronto Master Gardeners do not recommend home remedies, so cannot comment on the use of vinegar, etc. What you and your husband have observed is a plant’s reaction to pruning: it is basically stimulation to produce more growth. This is why you will often see new shoots coming out of tree stumps. Removing the pavers and digging up the root (making sure you get the entire root) would be the fastest way to permanently remove these young trees. Our recommendation, if you are not keen to remove the pavers, is to continue to cut these saplings off as close to the ground as possible, or even slightly below ground if there is room between your pavers to do this safely using a sharp tool. This will eventually starve the roots of the energy they need to produce leaves, and without leaves to continue to provide energy to the plant, they will die. If you’d like to keep one example to leaf out, we could hopefully provide a clear identification, but our advice would likely remain the same.