Answer: Daffodil bulbs do proliferate and the clumps can become crowded as a result, with decreased flowering being an indication of that. You can lift the bulbs, separate them, and replant further apart. Usually the bulbs separate themselves when you dig them up. Try not to damage them when you dig. You may find many small bulbs along with larger double and even triple nosed bulbs. Replant them all as they will all eventually bloom.
The best time to dig them is in the summer once the foliage has died back and dried up completely. Then you can replant immediately or store for planting in the fall. (Air dry for a few days, then store in a paper bag or on a shelf in a dark and airy place at room temperature.)
You might still be able to dig and move them now. The bulbs begin to root in the fall when the soil temperature starts to cool down. If the bulbs have not started to grow roots yet you can separate and replant them now. To see if they are still dormant, dig up a few and check the base of the bulbs. If you see no signs of root growth, go ahead and move them now. If they have started to root, wait until next summer.
Other reasons why they may bloom less include reduced sun (they do best in full sun locations) and trimming the foliage off too early in the spring. The foliage needs to grow and then fade naturally, this is the process that rebuilds the bulbs so they can bloom again the following year. One more reason is lack of nutrients. If your soil is poor, you could top dress with compost each fall and/or use a granular fertilizer such as 10-10-10 each spring as they begin to come up.
Good luck with your daffodils!
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