I would like to remove a tree stump that is a couple of feet away from my house. It's starting to rot, and I'm afraid it will get lots of insects. I'd have a professional crew do the job, but I suspect the stump is too close to the walkway to be pulled out without causing damage. I have a container of commercial stump remover, which contains potassium nitrate. My concern is that rainwater might splash some of the stuff onto my house, potentially causing its frame to rot. What do you think?
Since the tree stump on your property has begun to rot already, my advice is to skip the chemical stump remover. Potassium nitrate-based products are meant to promote the activity of wood-devouring microorganisms. They are busy on your stump to begin with, so why not simply let the rotting process continue?
If you are intent on using the chemical, start by cutting the stump as close to grade as you can. Next, use a drill (outfitted with a 10-inch or longer bit) to drive multiple holes into what remains of the stump. Then fill those holes with the chemical (granular, liquid, or powder), following the manufacturer's directions.
In a hurry? Hire a pro. You doubt that the stump could be pulled, given its proximity to a walkway, but in fact pulling is only one of many ways to remove a tree stump. In your case, the crew would likely use a grinder. Though powerful, these machines can operate successfully in a tight space. With the stump removal job in experienced hands, all that you would have to do is add new soil and some lime (to counteract the acidity that rotting causes), then plant your petunias.
If you'd rather not pay to have the job done for you, consider renting a small stump grinder (the fees are modest). With these smaller units, however, the major drawback is that you can probably only grind the stump to a level one or two inches below grade. Replanting the area, even with annuals, might prove impossible.
For small- and medium-size stumps, you can always perform manual removal, though of all options, this is by far the most labor intensive. First, dig a trench around the stump, exposing roots as you encounter them, cutting them with a pruning saw, heavy-duty shears, or an axe. Keep digging until you are able to fit a long pry bar under the main root ball. Continue to pry on all sides, exposing and then severing the roots that were hidden at first. Finally, lean the root mass to one side and cut as deeply as you can into the taproot. The stump will gradually break free from the soil. Assuming the stump isn't huge, you can be done within a few hours.