HO-99
Growing Annual Flowers
HOME YARD & GARDEN • COOPERATIVE EXTENSION SERVICE
DEPARTMENT OF HORTICULTURE • PURDUE UNIVERSITY -WEST LAFAYETTE, IN
Michael N. Dana
Most home gardeners consider annuals (plants which complete their growing cycles within one growing season) among their favorites. Quite versatile, annuals are suited to a variety of uses and conditions. They are inexpensive, available in many shapes, sizes, and colors, and most produce abundant blooms. Today, the petunia, marigold, and zinnia are most popular, but there are many other annuals which are both practical and easy to grow.

Uses
Annual flowers can be used in many ways. They may be planted among perennials in a perennial garden, among foundation plantings as a low-growing hedge or border, or in planters, boxes, or urns as accents. For landscaping, annuals provide a mass of color in contrast to the dark foliage of ornamental shrubs. Often they are planted to fill in newly-established shrub beds and to overplant bulb beds, providing color after spring flowering bulbs have faded. Many annuals are appropriate as cut flowers and some for dried, winter arrangements (see Figures 1, 2, 3, 4).
While most annuals will bloom well all summer long, some, like the sweet pea, are not well-adapted to the summer heat. Some dwarf forms, the marigold and salvia, for example, will flower early, while the giant forms flower later. Selection according to a desirable height is also possible with such annuals as the snapdragon and zinnia.

Location
Most flowering annuals grow best in the full sun and in well-drained garden soil. Except for shade tolerant types, the plants grown in the shade are spindly and produce fewer flowers (see Table 1). Those placed in wet, heavy soils also grow poorly. Before selecting a definite garden site, check for drainage. Dig a hole 10 inches deep and fill it with water. After that water drains, refill the hole with water. If that water drains away in 8-10 hours, the permeability of the soils is acceptable for growing annuals.
Also check the sowing recommendations. Some seeds, such as poppy and sweetpea, should be sown in their permanent location, whereas most annuals can be transplanted.

Soil Preparation
Organic materials such as sphagnum peat moss, leaf mold, compost, and rotted manure should be applied early in the spring. Spade or rototill the soil to a depth of 8-10 inches, being sure to incorporate the organic materials thoroughly. Work the soil several weeks before planting in the spring. If no plants were grown in the area the previous year, the organic matter should have been worked into the soil the preceding fall.
If annuals are to be started from seed in the garden, the bed must be level and the area raked smooth after the final soil preparation. Remove all stones, clods, and old plant refuse.
Little soil preparation is necessary for annuals planted in bulb or shrub beds. These beds should have been well prepared when they were established. Still, a light cultivation, along with some additional organic matter, is often beneficial for getting annuals established in these areas.
Annuals for container growing should be grown in new soil each year. A potting mixture of garden loam, sphagnum peat moss, and vermicu-lite or perlite (1:1:1 by volume) is satisfactory. For good drainage, drainage holes in the bottom of the container or at least 2 inches of crushed rock or gravel are necessary.

Fertilizer
Fertilizer should be applied when the soil is prepared. Use 1 to 2 pounds of 5-10-5 or similar analysis fertilizer per 100 square feet of bed area. If the soil fertility is low, additional applications may be necessary throughout the growing season. Usually, 1/2-1 pound of 5-10-5 per 100 square feet every month to six weeks will suffice. For home gardeners, an easy conversion is to remember that one pound