Dear Jim; L. aurea is more common than L. traubii in garden centers. It really isn't happy much north of Zone 8. The most obvious difference is the size of the plants with L. aurea foliage approaching 3 feet in length while L. traubii rarely gets to a foot in length. L.aurea flowers are bright 'pure' yellow, while traubii's smaller flowers are more golden yellow. L. chinensis is usually available from Plant Delight's Nursery and Fairweather Gardens as potted bulbs. Caldwellii is also sometimes available from both too, but not always. Both have web sites. I didn't mention the also hardy L. straminea really as straw yellow to tan color that is fairly dull in the garden. All these yellows should be quite hardy for you. Best Jim W. -- Dr. James W. Waddick 8871 NW Brostrom Rd. Kansas City Missouri 64152-2711 USA Ph. 816-746-1949 E-fax 419-781-8594 Zone 5 Record low -23F Summer 100F +