If you alter the plants on your planter box frequently, leaving them in their pots makes the job easier. Leaving nonhardy plants in their pots also makes it simple to pluck them in the planter, clean them off and take them indoors for winter. It’s not a good idea to leave small plants in 4-inch pots unless you are scrupulous about boating, though. The little root space their pots allow wo not be enough to stop them from wilting in hot weather. When you utilize a huge planter box, you want to fill it with inert materials, position the pots and sprinkle all but the growing crops with a decorative mulch or covering.
Pick filler materials that will not break down or decompose over the growing season.
Fill the bottom of the planter with heavy materials to stabilize it. Use rocks, bricks, chunks of concrete or pieces of broken ceramic or terracotta pots. Arrange a mixture of materials to get the best fit.
Add inert filler to the planter. Utilize household cans, bottles and bags to take up space. Round up enough crushed aluminum pop cans, plastic milk jugs, plastic water bottles or wadded-up, empty potting soil and soil-amendment totes to fill the space up to the level in which you place the pots.
Establish the potted plants on top of the filler material or about upended nursery pots to position them at the correct level. Ask neighbors for their empties or recycle a few from a nursery’s pot-return bin or even the local plastics-recycling center.
Use a lightweight filler material like the plastic foam peanuts that protect mailed products. Bag the peanuts in little plastic bags so that they do not blow away and position them around the pots to hold them in position. If you do not have packing peanuts, arrange blocks of foam in the planter.
Top the planter with dried moss, landscape cloth covered with ornamental stones or other material to hide the grass rims as well as the filler material.