Winter Aconite

One of the perks of buying an older home is what may pop up in the yard in the spring. Here are some winter aconites (Eranthis hyemalis), a long-blooming bulb that spreads around. They're much easier to see since the English Ivy was pulled out.
As with a number of other exotic species, it can spread in the garden, but doesn't seem to make the leap into local nature preserves, where it would not be welcome.
Don't confuse it with Lesser Celandine, which has become a seriously invasive weed, carpeting lowlands of Princeton preserves. They are in the same plant family (buttercups), and have similar flowers that open in late winter, but the leaves of Lesser Celandine are round.