I fill most of the planter with rocks if it is plastic or light materials. And polystyrene for heavy planters. Fill it up 3/4 then add soil to the top and add your plants.
Anita is right above. Be sure to put something in the bottom to let the water drain but not your soil. I don't fill it with the drainage material to 3/4 full, just about 2 - 3" will work but it is a case of what you prefer. More drainage material and less soil or the other way around. Happy planting :)
Drill holes around the bottom. Fil bottom 1/3 with broken up Styrofoam or other material. Then add soil.
You can put anything in large planters you can do ornamental grass and then some small flowers around them in different heights to make it look very pretty we can do vegetables in large planters trees and large planters anything to decorate where you want them to go