So why plant Eranthis instead of a yellow Crocus? Primarily because it is ideal for shadier (deciduous shade), more woodsy locations, with humusy soil that is moist in winter and early spring; while Crocus prefer sunnier, better-drained positions, such as in my sun-baked front lawn slope.
Of course, either bulb will tend to make a minor impact, unless it is present by the hundred. Eranthis, like some but not all Crocus varieties, is known for multiplying if it likes its location. My small planting is an experiment to discover if it likes mine. I may add to it this fall, but I am always prepared to wait for results that may be obtained cheaply (5 bulbs for $2).
I bought the bulbs at Ward’s Nursery down in Great Barrington, which is pretty far away, but had a far better selection of bulbs than any other place I visited last fall. (As far as I know, you can’t find Eranthis in the Northern Berkshires.) If you have a lightly wooded area, or a shrubbery, I recommend you give them a try. (They won’t do well under evergreens.) While Eranthis’ greenery disappears by midsummer, when shade and dryness makes their position inhospitable to most plants lower than their overtopping shrubs or trees, their presence in the spring is reputed to stifle most weeds.
I have never noticed these bulbs other than in a botanical or open-to-the-public garden. I suspect there is a “chicken and egg” problem here, given that they've never heard of them even in most places selling bulbs. Do you have experience with them, or questions?