Pick an area with full sunlight to plant the circular garden. Put a garden stake in the center of the selected area. Cut a piece of twine or string measuring 9 1/2 feet long. Tie one end of the length of twine to the garden stake; tie the opposite end to a can of spray paint. Pull the can of spray paint as far away from the stake as possible. Spray a circle around the garden stake. Keep the string taut as you spray to make sure the circle is perfect. Remove the garden stake.
Use a small garden tiller to till up the dirt in the garden area. Use the spray paint as a guide for the shape of the circular garden. The tilling process will prepare the soil for planting.
Install desired garden edging around the perimeter of the garden. Edging prevents weeds from growing and taking over the garden and adds aesthetic value.
Plant five Joe Pye weed plants (Eupatorium maculatum) in the center of the garden. Dig the holes for the plants in a circular pattern, leaving about 6 inches between each hole. The holes should be 1 inch larger than the diameter of the plant pots. Loosen the soil around the roots and place the plants in the holes. Cover the base of the plants with soil. Joe Pye weed plants are very tall and make a lovely center point for a circular butterfly garden.
Plant small clusters of swamp milkweed (Asclepias incarnata) plants around the Joe Pye weeds. Plant these plants the same way as you did the Joe Pye weeds. Leave 12 inches between each plant.
Plant small clusters of New York asters (Aster novae-angliae) in between the clusters of milkweed. Plant these in the same manner you planted the previous plants. The asters and milkweeds will grow up together and create a smooth layer of blooms below the Joe Pye weeds.
Plant large clusters of zinnias (Zinnia elegans) in front of the swamp milkweed. Plant the zinnia plants in the same manner as the previous plants. Leave about 2 inches between each plant. Fill in the gap between the milkweed and the edge of the garden entirely with zinnias.
Plant clusters of parsley in between the clusters of zinnias. Plant the parsley the same way as the other plants, leaving 2-inch gaps between each plant.
Spread a thin layer of garden mulch over the entire garden area. Use a small, hand-held rake to distribute the mulch. Avoid covering the plants with the mulch.
Water the flower garden thoroughly once planted and every day for several weeks until plants take root.