Spacing largely depends on the mature size of the plants. Be mindful that spacing plants too close together stunts their growth and increases the chance for disease problems. Regarding annuals, ageratum, lobelia, pansies, dwarf French marigolds, and sweet alyssum should be spaced 6 inches apart. Begonias, dusty miller, nicotiana, petunias, and dwarf salvias should be spaced 8 inches apart. Ten inches apart is a better spacing for calendula, celosias, gomphrena, hypoestes, impatiens, large marigolds, snapdragons, and zinnias. Large geraniums should be spaced 12 inches apart, while melampodium and spiderflower (cleome) should be spaced 14 inches apart. For more uniform beds, use a triangular spacing instead of a straight row or a rectangular grid. Triangular spacing requires more plants per square foot, but the resulting effect will be more attractive than plants placed in rows. For spacings of six, 10, 12, or 14 inches between plants, you will need roughly 48, 28, 16, 12, or eight plants respectively per 10 square feet. Herbaceous perennials such as daylilies and salvias should be spaced according to their mature spread. Space low-growing, front-of-the-border plants about 12 to 18 inches apart. Plants of intermediate size should be placed at least 18 to 24 inches apart (three to four plants per 10 square feet) and larger plants should be spaced about 3 feet apart.

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