Fiberglass planters are ideal gardening containers as they can be made in a multiplicity of shapes and sizes and be finished to mimic a range of more costly and heavy materials from iron to terracotta. As with all container gardening, good drainage is paramount. Fiberglass containers typically come pre-drilled with drainage holes or pop outs or holes can readily be created in the fiberglass with a household drill or awl. Lightweight potting mix helps keep the containers mobile even when filled to capacity.
Prepare the container for planting by drilling one or more small drainage holes in the bottom of the fiberglass pot. Make the diameter of the holes roughly 1/4-inch.
Fill the fiberglass container roughly halfway up the sides with lightweight bagged potting mix containing perlite and or vermiculite. Test for plant height as you want the plant to sit at the same level in the soil as it occupied in its previous location. You also want to maintain at least 1 inch of space from the soil surfaced to the lip of the container to act as a watering catch. Add or remove soil to achieve this.
Place the plants in the container, tucking soil around the root ball and filling in any air pockets. Water in the newly planted container deeply until drenched and a small trickle of water is visible from the drainage hole.