Alaskan fish fertilizer works well for the organic gardener. Miracle Grow, a common vegetable fertilizer has been known to work well. Be sure to follow the directions! If possible, a slow release or times released fertilizer will be ideal since they do not release until the temperature reaches the mid to high seventies, by which time they will be the ideal height.  This type of fertilizer lasts for three months, which is just the right time for nitrogen levels to taper off, thus promoting flowering.