Beurre de Roquencour beans are an heirloom wax bean that came out of France around 1860. Its origins beyond that are unclear. Because it is a stringless bean, however, it may have some ancestry to beans developed by a New York plantsman, Calvin Keeney. But the dating of Keeney's beans and stringless French beans make it unclear of who begat whom.
The term "wax bean" is a New England colloquialism for "yellow beans" that has become widely adopted in the seed trade in America. A second inference of the term is that the beans are straight and thin.
Beurre de Roquencour beans are a semi-bush variety. French growers in the 1800s developed many bush varieties from pole beans. There was a strong interest in such beans since they could be grown in a glass house environment. Many wealthy estates had these early "green houses" which supplied the owners which fresh vegetables over an extended season.
Now considered an heirloom, Beurre de Roquencour are principally grown by home gardeners in France. Their lack of disease resistance and habit of slow-paced pod development make them unattractive candidates for commercial use. But commerce's loss is our gain. This French classic turns out loads of beautiful beans with remarkable tenderness and flavor. Their flowers are also amongst the most attractive of bean flowers that I've seen.
An ideal method of preparation is to boil full-length beans in a large excess of water. Then nap the beans with a restrained quantity of melted high quality butter seasoned with finely cut fresh herbs. Dill or tarragon makes for a memorable presentation. Add crushed finishing sea salt to taste. It couldn't be simpler. Nor better.
These beans were grown organically in my garden in the Valley of the Moon.