The false spirea, or astilbe plant, is a showy flowering perennial. The astilbe flower come in lots of color varieties, including purple, pink, white and red. The flowers are plumelike, appearing in June and July. Proper fertilization and care of the plant ensure that its flowers look their best.
Plant astilbe into a humuslike soil that is full of organic matter in the spring or fall. The organic matter provides a slow-release fertilizer to the plant throughout the season. The astilbe is a heavy feeder that requires lots of nutrients. Plant the astilbe plant in a partially to fully shaded area to protect it from the heat of the afternoon, which damages the flowers.
Fertilize the astilbe plant early in the spring to produce healthy flowers. Astilbe requires a 5-10-5 fertilizer blend says the University of Maryland. This helps develop the flowers. Another application of fertilizer is required in the summer after the plant has come to bloom. A small handful of fertilizer sprinkled around the base of the plant or a liquid fertilizer sprayed on the foliage in July should do.
Properly fertilize the plant to make propagation successful. Fertilizer creates deep and healthy roots, which is important in the division process necessary for the propagation of astilbe. Divide the roots of the plant in the spring or fall when the plant is dormant. Plant the root crowns shallow so that new shoots are covered with 1/2-inch of soil. Place the plants 12 to 24 inches apart and water until established.
Disease may occur if proper fertilization is not heeded. Powdery mildew attacks weakened plants, developing in humid conditions. Cut back the foliage of the plant and ensure it is fertilized properly. Fusarium wilt occurs when there is not adequate soil drainage or aeration. This traps nutrients and makes them unavailable to the plant. Astilbe is resistant to disease when fertilized properly.
Water astilbe to keep nutrients moving through the soil. Astilbe will not grow in dry soil. Keep the soil moist but not wet by hand irrigation if there is not sufficient rain in your area. Too much water is harmful as well. Ensure that the soil around the plant has good drainage for the winter months to prevent dieback. Remove any dead plant matter in the spring before fertilizing.