One of the best ways to add bright colors to a flower garden is to plant annual flowers. In addition to flowerbeds, annual flowers are excellent plants for hanging baskets, borders, cutting gardens, flower boxes and around the bases of trees. Sometimes these flowers are grouped into warm-season or cool-season annuals. While warm-cool annuals, such as four-o'clocks, do better in daytime temperatures in the 80s and 90s, cool-season annuals, such as petunias, thrive more in daytime temperatures in the 70s and 80s.
Unlike perennial flowers that continue to bloom for several years, annuals complete their entire life cycles in only one growing season or vegetative period. In other words, annuals live their lives from a seed until a new seed crop. Annual flowers develop during spring and summer and then die in autumn.
Advantages and Disadvantages
Annual flowers allow gardeners to try out many different flowers of various colors, textures, heights and forms. If the wrong annuals were planted, they can easily be replaced the next year. Besides adding color and versatility, annuals need less weeding than perennials because a garden can be turned over before planting them. Annuals are easy to grow and gardeners don't have to wait long for flowers to bloom.
A disadvantage is that annuals are not overwintering plants and need to be replanted every spring, creating added expense and time. Another disadvantage is that old flower heads need to be removed weekly for plants to continue to bloom.
A few of the most popular annuals include geraniums, marigolds, pansies and salvias. Germaniums come in various colors and can tolerate light frost. They grow in full sun and are not bothered by deer as are most flowers. Marigolds are bright, cheery, yellow flowers and should also be planted in full sun. Pansies are popular spring flowers because they can tolerate a frost and colder weather. Salvias need plenty of sun and are resistant to deer.
Considerations and Tips
Consideration should be made regarding soil. While some annuals such as geraniums can take dry soil, others such as impatiens do better in moist soil. Labels on seed packets indicate conditions for a particular annual so it's important to read them before choosing a plant.
Mulching is recommended as it keeps soil surfaces from crusting and helps in controlling weeds. Organic mulches are even better because they're able to add humus to soil. Grass clippings are also used as effective mulches.
It's a common misconception that a flower is either an annual or perennial, but there are some flowers that fall into both categories. For example, some perennials, such as begonias and snapdragons, are considered annuals because they can't survive wintry conditions and have to be set out every year.
Gardeners shouldn't rush to start their seeds outdoors. It's better to delay sowing seeds of warm-weather annuals until after the last frost date. According to the University of Arizona Cooperative Extension website, most seeds will have trouble germinating in soils that are below 60 degrees F.