My friend Mac Pike who is a wiz in the vegetable garden asked about daffodils and when and how to go about dividing them. So, I figured I'd answer him (and anyone else who would like to know) right here.
Daffodils grow from fleshy bulbs, as you may know. They get their energy for next year's flowers after they finish flowering this year. How? Through their leaves from the sun. You have heard of photosynthesis, I'm assuming. It's truly one of the most amazing things about plants, their ability to take the sunshine and convert it into food and energy which then gets stored in the bulb and lies dormant until the next spring comes.
Another thing bulbs do is multiply. They do this two ways. First the bulbs will naturalize, which is just a fancy way of saying they will flower and the flower if not snipped off the plant will go to seed. These seeds will drop and start to grow a baby bulb which eventually grows big enough to flower on its own, perpetuating the species. Naturalizing bulbs keep growing and spreading for bigger and better spring time displays.
Bulbs also expand by growing from the bulbs themselves. That is to say, the bulbs get bigger and then split into smaller bulbs or bulblets. These eventually get crowded and need to be divided to help the bulbs stay strong and so they flower more abundantly. If they get too crowded and you leave them, bulbs may eventually not get enough food and they start to die off. So, it is advisable to divide them when the colonies get a bit too big.
To divide the cluster of bulbs, you need to wait until the foliage dies down. It is the foliage that gives them the energy from the sun, so keep these until they dry up. That is when it is safe to dig up the bunch. To be safe, use a straight-tined pitch-fork to loosen up the clump. Shovels could cut into the bulbs but if you dig several inches away from the edge of the clump it should be okay. I find it easier to use the pitchfork.
Once dug up, carefully twist the clump back and forth to loosen up the dirt and to separate individual bulbs. One good clump can yield a great deal of new bulb for you, enough for you to expand your spring time display and to share with friends. Dividing daffodils bulbs is great for everybody!