Planting Instructions: Plant your dahlia in well-drained soil in a sunny location, with protection from the wind. Choosing a location with good air circulation will also prevent powdery mildew. Supply ample moisture and fertilizer during the growing season. When the plant reaches 1 ½’ in height, trim the entire plant to 1’. In about two weeks, trim the plant back again to about 1 ½’. This will encourage your dahlia to produce an abundance of flowers. Remove all spent flowers. In zones 7 and lower, these tuberous roots must be lifted from the ground after the first frost and stored in a cool dry place for the winter.