Once upon a time, bone meal was considered an excellent flower bulb fertilizer, but times have changed! Most bone meal today has been so thoroughly processed that the essential nutrients have been literally boiled out. Spring-flowering flower bulbs actually need no fertilizer for their first flowering season. A healthy Dutch flower bulb will already contain all the nutrients it needs to support one season of spectacular growth. Flower bulbs that will be left in the ground to naturalize will benefit from well-rotted cow manure or special flower bulb fertilizer when the shoots first appear in spring and again the following autumn.