since you are new to growing & this will be outside year round, do something temp for now
Get an empty pot & turn it upside down in the planter.Or get a piece of chicken wire & scrunch it up & shove in there. Then get some plants, in smaller pots, & place inside planter, on top of the fillert. This time of year, put a Mum out there. Come the holidays, a poinsettia. Pots of Spring bulbs in winter.
Solves the problem of a too heavy to move pot, & you can experiment with plants.
