Answer: Daffodils can be left in place for a number of years, but eventually they may need to be divided. If they are crowded they may not bloom, while another possible reason is that they must be allowed to ripen their foliage (the leaves should grow and then turn brown before removal) in order to replenish the bulbs from year to year. Yet another reason although less common is that they are in too much shade or are in a spot that is too damp or are simply a variety that is not terribly vigorous.
Iris can also become crowded resulting in reduced blooming, and as a rule of thumb would be divided every three to five years. (Cutting the flowers wouldn't cause it.) Iris do prefer a rich, well drained, neutral to alkaline soil, and the only way to know if you need to add any amendments such as lime or not is to run some basic soil tests. Your County Extension (285-4630) can help you with the tests and with interpreting the results.
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