The first cold-hardy, yellow –flowered Lycoris seem to have arrived here in the US back in the 1930s. That plant (or those plants, I’m not sure if they were clonal or not) was never widely distributed. I’ve heard that it eventually grew in the local garden of Bethesda lawyer Frederick Lee, chairman of the Advisory Council of the U.S. National Arboretum back then, although by the time I learned that, the garden had passed into new hands.
When China began to open up again about twenty-five years ago, yellow-flowered Lycoris began to trickle in again - and, they proved to be hardy. My plants came from Jim Waddick in 2008, and some of them answer to Lycoris chinensis. Some are L. longituba, and some are intermediate in their characteristics.
After this post was originally published, I've come back to add more images: the flower color has intensified each day and is now a strong chrome yellow. When I first noticed the inflorescence, I was not sure what color the flowers would have. The early buds were white at first, then a very vague flush of pale yellow appeared. You can see in the images above what finally happened.
Throughout the twentieth century there was (and still is) a plant in commerce which is a very bright yellow flowered Lycoris; but it is not hardy. This is Lycoris aurea, and you can read more about it here: