When considering a fertilizer for your flowers, first check to see if it's been tested on the type of flower you'll be growing. Many manufacturers only do limited testing so using their products can be something of a gamble.
Of course, the fact that a product has only received limited testing won't be announced on the package. However, manufacturers who go to the expense and effort to test their products on a wide variety of crops will generally announce this on the container or in their literature.
You also want to make certain the nutrient is formulated for flowers. Otherwise, the
product may contain too much nitrogen which will end up giving you more leaves than
flowers. The rule of thumb is that using any un-balanced fertilizers for the type of plants you are growing will result in a lower yield and affect the fragrance and taste.