Jim
Your large -flowered robust lesser celandine is Ranunculus ficaria ssp
ficariiformis. It is sometimes called R f ' Major ' in older horticultural
literature.
The smaller weedy one is R f ssp bulbifer which has bulbils in the leaf
axils allowing it to spread in an alarming way. It is this form which gives the
species a bad name.
Many of the choicer cultivars are derived from R ficaria ssp ficaria
which doesnt have the above-ground bulbils. They however must be dead-headed to
prevent spreading by seeds. Many are worth the effort.
Jerry John Flintoff
Vashon Island,Washington,USA
Zone 8