Hi Dave, In my experience "Ipheion sellowianum" will grow in any well drained 'soil' in a pot. I certainly wouldn't mess about with clay. I think it is more important to mimic the environmental/seasonal conditions that plants are exposed to in habitat rather than duplicate the exact physical conditions. Best, J. John T Lonsdale PhD 407 Edgewood Drive, Exton, Pennsylvania 19341, USA Home: 610 594 9232 Cell: 484 678 9856 Fax: 315 571 9232 Visit "Edgewood" - The Lonsdale Garden at http://www.edgewoodgardens.net/ USDA Zone 6b