If an unwanted seedling is growing so close to a desired plant that it would be necessary to dig up both plants to get rid of the seedling, I don't consider digging as a realistic option. I use a tiny paintbrush to apply brush killer immediately after cutting, as Al described, and it does work. I don't throw the paint brush out, but I have dropped 3 of them into the jug so far.
A pack of a dozen little paintbrushes should be less than $2. The jug of brush killer was more expensive but at the rate I use it, it would last at least 100 years. They should sell tiny bottles of it, especially if it degrades over time. An ounce of it is enough to kill at least several hundred wayward saplings.
