Plannn* with three Ns is a high probability typo made by cataloguers who don't put enough planning into their keystrokes. It might be a typo for all sorts of words beginning in plann* or even plan*, if a typist leans on the N key hard enough. Planned, planner, planning, plant, planet, plane, plankton...
This summer I'm left wondering who planned the plants in my yard before I moved to this house. While my walnut tree is lovely and provides plenty of shade, it also gives squirrels a nice perch to throw nuts at me from above. Worse, it releases a chemical called juglone that kills many plants around its roots.
So if you have a walnut tree, plan ahead and do some research about what to plant, or you'll find your tomatoes and forget-me-nots dying a quick death, like mine.
(Image of the chemical structure of juglone from Wikipedia)