Plant the flowers or plants in mid-spring to give them a full summer of growing. Move the rotating drum to a site with bright sunshine and good air movement. Turn the drum on its end, with the open side facing upward.
Fill the bottom half of the drum with blocks of wood, bricks or wood chips to take up room, rather than filling the entire drum with expensive soil. Wood or brick also provides a place to catch water and keeps the plants from sitting in muddy soil after planting.
Create a potting mix with 1 part organic compost to 1 part garden loam or 1 part peat moss to 1 part garden loam and 2 parts vermiculite. These mixes provide drainage, nutrition and moisture retention for potted plants. Add 5-10-10 granular fertilizer for more nutrition. Fill the top half of the drum with this mixture.
Plant flowers and plants according to your preferences. Put sun-loving annuals, like mums and marigolds, in the sunny areas and supplement with shade-loving violets and primroses in shady areas. Use trailing ivy or nasturtiums for vining, decorative growth on the sides of the drum.
Water the plants with 2 inches of water every week to keep the soil moist. Give plants all-purpose water-soluble fertilizer every month during the summer.