We use a couple of different "tricks" for pot plans:
1. We have a full set of blocks with letters in a circle (a-z) that we use as generic symbols (LOVE THESE! We use them often). We will often use these to "count" things like the planters itself, while still retaining a generic graphic symbol on the XREF'd site plan drawing. We typically put these on a new separate NPLT layer (We duplicate the L-SITE-BLKS layer and add the suffix -POTS). This is very similar to the "dummy" block that you use, but keep the smart aspects for running schedules.
2. We use work areas to run different type of pot schedules. Maybe you have 3 different types of planting configurations and want a schedule for each. Maybe you want a schedule based on location. When we run the schedules, we sometimes rename the schedule title (manually) to ensure that it is labeled clearly for the contractor (ie., Plant Schedule A - Small Round Pots).
3. For reducing graphic clutter, put plants off to the side of the drawing. We'll but a large NPLT rectangle and label that this is the location for the plant or refnote blocks/hatches/lines to go. Keep this area tidy with NPLT labels.
4. Keep nomenclature consistent. So, for planter A, we'll use the (A) generic symbol, then add the "A" to the refnote number, in the refnote note we'll label it "A - Small Round Pot", and label the work area "A - Planter". That way there is consistency across the drawing. We'll then run a schedule for the pots (refnotes) and for the plants in each pot (work area). Depending on whether the pots are the only planting or not, you may want to run a full planting schedule too. We put the full quantities on the planting schedule and then put pot specific quantities on the container and planting plan. We think of the container and planting plan as the plan that is used on the ground for installation, but the full planting plan as the one used for estimating/ordering plants (again, we typically have ground and pot installation).
5. Create a block that is your detail title block. We use this for labeling viewports that show locations of pots. (Actually, we use it for labeling most viewports). You can also have viewports showing the locations of plants in a single pot.
6. I think the most critical part of setting up a pot planting plan is thinking about the final document and how you want it to look and what information you want to show. Then working backwards.
Hopefully this helps!