A flat head screwdriver can be indispensable, in my opinion. They come in various sizes, so you can choose what might work best for you. A (horse) hoof pick is kinda like screwdriver variant, and you might want to at take a look at that, too. The table knife (butter knife) works really well loosening the soil along the trough sides, especially. Tweezers can be very useful, especial in an arboretum setting when you are not there all the time to catch weeds at their most vulnerable stage. Table forks also have their place. I find dental tools are too flimsy. For me, this causes a spring action that often sends dirt and pebbles flying. A nut pick works much better. Dental tools are very useful dealing with seeds and seed harvest extraction. Sometimes all you need is something stiff the size of a 6 inch crochet or knitting needle, to loosen the soil to pull weeds out. Small scoops found in the store cooking utensil section easily directs the soil where you want it and not where you don't.
Edited for grammar.... yow...
