How to Care for Dahlias
You can continue to fertilize with a high-phosphorus fertilizer approximately every 3-4 weeks to encourage blooms. Over fertilizing will lead to bushy growth with smaller blooms. In the Fall, after the plants have died back, cut your growth down to about 2 inches above the surface of the soil. Carefully dig out your dahlia tubers that have developed and remove any excess soil. Dry for 1-3 days, and store in cool, dry conditions with little exposure to sunlight. Your Dahlia tubers can be planted once again the following Spring.