How do daffodils spread?

Daffodils do not go to seed. The grow from bulbs ( the main root of the plant. ) I usually tear apart my daffodils every 4 to 5 years and separate the bulbs, and replant them in different locations.

On a side note . . . Deer detest daffodils, so they are a great flowering plant to grow if you have a large deer population.

Daffodils do produce seed. Seed from species will come true to type and can take a few years to produce flowers. Hybrids will not come true from seed so are multiflied by various manipulations of the bulbs.