Thanks for writing. These sweet potatoes are ornamental varieties -- so unfortunately, you won't be able to find them at the grocery store.
That said the sweet potatoes from the grocery store are easy to grow and will grow just as fast, producing green foliage instead of the bright yellow-green of 'Marguerite'.
Look for 'Marguerite' at your local garden center or nursery this spring.
---Justin, Senior Garden Editor, BHG.com