What is the collective noun for a collection of daffodils?

The most common collective noun for a collection of daffodils is a cluster.

However, you can also use these:

* Field

* Patch

* Bunch

* Tufts

The best choice will depend on the specific context. For example, "a field of daffodils" might be better for a large, open space, while "a bunch of daffodils" would be better for a smaller, more contained group.