Forsythia plants are deciduous shrubs that are part of the olive plant family. These fast-growing plants produce beautiful flower blooms in the early spring, and maintain their color through the late fall. Forsythia species are hardy, resilient and don't have major problems attracting pests or other insects. The plants thrive in full sun, but they can also survive in partial shade. Like most shrubs, forsythia plants should be fertilized occasionally to promote health and growth. Following a few key steps helps ensure a healthy forsythia year after year.
Do not fertilize newly planted forsythia shrubs. Instead, wait until the plant has been growing for about one year before applying any fertilizer. Apply 1 cup of granular fertilizer around the base of the forsythia. Spread the fertilizer about 18 inches beyond the tips of the branches. This allows rainwater and irrigation to soak the nutrients into the ground along the root system of the forsythia shrub, which can extend several feet away from the base.
Mature forsythia shrubs require little in the way of fertilizer, as they are resilient plants that can grow up to 2 feet in a single growing season. Up to 1 cup of an all-purpose garden fertilizer can be spread around the forsythia at the beginning of each spring growing season when growth is poor. As a general rule, forsythia shrubs do not require fertilizer or other soil amendments to be successful.
Selecting a Fertilizer
When you apply a fertilizer to forsythia shrubs, it's important to select the right kind. All-purpose fertilizer with a balance of nitrogen, phosphorous and potassium is best, as these three nutrients promote root growth, color and flowering. However, it's also appropriate to use fertilizer that contains higher amounts of phosphorous. Phosphorous leads to brighter flower blooms and more vibrant colors in the spring blooming season. The concentration of phosphorous is denoted on the fertilizer's label as the second of three numbers. For example, a bag of 10-10-10 fertilizer contains a balanced blend of 10 percent nitrogen, 10 percent phosphorous and 10 percent potassium. A fertilizer with a 10-15-10 rating includes higher levels of phosphorous.
There are several methods for applying fertilizer. Broadcasting is the method of distributing fertilizer along and entire crop or field. This is a good approach to fertilizing lawns, where the grass covers large areas. Foliar fertilizer is applied directly to the leaves of plants, as a method of reducing disease and protecting leaves. The third type of fertilizing, placement, is the most appropriate for forsythia plants. Placement means putting fertilizer on the soil around specific plants or plant rows. When fertilizing forsythia, spread the fertilizer only around the base of the shrub and its root system. This selectively targets the bush for fertilization. The best time of the year to fertilize forsythia plants is in the late fall.
Heath Roberts has worked as a professional reporter for several Colorado newspapers. He has covered breaking news and features for the "Denver Post" and other local publications. Roberts holds Bachelor of Arts degrees in both journalism and political science.