Annuals grow to adulthood, flower and produce seed in one growing season. The advantages of annuals are that one has a wide range of colors with which to design and experiment. In addition, your selections can be changed from year to year as you develop new design ideas.
Most annuals are selected for both blooms and foliage. Many bloom all summer once established. Annuals are classified as hardy or tender, depending on cold tolerance. Hardy ones, such as pansies, are tolerant of frosts and have color through the winter. Tender annuals are very cold sensitive. Many of these, such as begonia, impatiens, coleus and petunias, are tropical plants often from regions such as South America where they may be perennials.
Selection and Design: There are many factors to consider, not the least of which is the site of your garden. Some annuals need full sun, others must have some shade, so you will need to match the plant to your site. Most all prefer fertile well drained soil.
Before you purchase and plant annuals, you should sketch out your garden, keeping in mind your design preferences such as color, height, texture, and form. The results are seldom satisfactory if one simply plants annuals without a plan. Clashing colors, incompatible heights and unattractive overall design often results. There are excellent books and websites to help in this regard.
Don’t forget the excellent usage of annuals in containers and window-boxes. They may be planted alone or in combination with other annuals such as ornamental grasses for an attractive effect.
Planting: The options are either to sow seeds directly or buy transplants from your local garden center. Like vegetable sprouts, annuals may be started indoors a couple of months before planting time.
The time to plant depends on the flower. Pansies should not be planted in the fall until the soil cools. They cannot tolerate heat. Impatiens and vinca must have warm soil, at least 70°, to survive. Information on current local soil temperatures are available on the Oklahoma Mesonet site.
Most annuals benefit from well composted organic material worked into the planting bed, especially in high sand or high clay soils. Its best to base fertilizers on a soil test result. If a soil test is not available, a slow release balanced fertilizer (one having all of the three major nutrients—nitrogen, phosphorus and potassium) such as Osmocote, is useful if tilled into the soil before planting. As with most plants a loose mulch added to the bed after planting will conserve moisture, moderate temperatures and help prevent weeds.
Spacing is different for each annual, but try to plant is such a way that they will fill in without being crowded. Some tall annuals will also need staking in areas exposed to the wind.
Fertilization: After planting; fertilization, irrigation and weed control are important. Most annuals grow and bloom continuously, which requires a steady supply of nutrients. In beds where a balance fertilizer was added at planting, or a bed that has been fertilized in the past, nitrogen (the first number on the fertilizer container) is all that is needed. Use a quick release preparation, either liquid or granular, according to the label. Lawn fertilizer without herbicide or insecticide is readily available and useful.
A generic amount of a granular fertilizer to use is one tablespoon per plant of a 30% and 2 tablespoons for a 15% nitrogen preparation. Percent nitrogen concentration is always the first number on the bag. Depending on the fertilizer used, fertilize again one month after planting. Some fertilizers will recommend different frequency, always follow the labeled directions.
Irrigation: Extra water is needed for all annuals in our area—at least 1 inch of water per week either by irrigation or rainfall. Sandy soils will need more water than clays. Water requirements vary, some annuals are more drought tolerant than others. Annuals with some drought tolerance are listed in the reference web page.
A drip irrigation system is relatively easy to set up, economical and much more efficient and effective than hand watering. It only needs to be set up once and should be functional for several years. See Drip Irrigation in this web site.
Weed control: Weeds are always a problem. Hand pulling and a good layer of mulch will control most. There are some preemergent herbicides, such as the Preen products, that may be used before or after planting to prevent weeds.
In our area Bermuda grass is often a problem. Herbicides are available which are fairly specific for Bermuda and which may be safely sprayed directly on most annuals. The herbicides contain ether sethoxydim (Over-the-Top) or fluazifop (Ortho-Grass-B-Gon) and are available in most garden centers. Always read and follow the labeled directions about where they may be sprayed.