Today’s summer flowering annuals have been bred to produce blossoms over an extended period of time. Because of this, if can be very beneficial to provide additional fertilizer throughout the growing season. This can be done either by the application of liquid fertilizer or by sidedressing plants with granular fertilizer. Sidedressing is simply adding fertilizer on or around the sides of the plant and then lightly scratching it in before watering.
For annuals, a high nitrogen side dressing four to six weeks after flowers have been set out will provide a good boost to their growth. Continue this every subsequent four to six weeks for best results. Kansas State University recommends the following fertilizers and rates. Do not over apply.
• Nitrate of soda (16-0-0): Apply 2/3 pound (1.5 cups) fertilizer per 100 square feet.
• Blood Meal (12-1.5-.6): Apply 14 ounces (1.75 cups) fertilizer per 100 square feet.
• Urea (46-0-0): Apply 4 ounces (½ cup) fertilizer per 100 square feet.
Check with your local garden center of nursery for these fertilizers. Or if they are not available, use a high nitrogen (first number of the three should be between 20 and 30) lawn fertilizer. Apply this at a rate of approximately ¾ cup per 100 square feet. However, be sure not to use a lawn fertilizer that has weed preventer or weed killer.