I'm no expert on medicinal plants but I'm fairly certain you want Tilia americana rather than the European species. Much of SE Minnesota was Maple-Basswood forest prior to European settlement. Diana Beresford-Kroeger is a big proponent of American Basswood.
Most decent nurseries should be able to order American Basswood for you if they don't stock it, although Ms. Beresford-Kroeger would probably recommend starting with seed collected from old growth forests. If you want seedlings you could try Cold Stream Farm in Michigan
or Oikos Tree Crops, also in Michigan.
I'm sure there are many other possible vendors although I don't off hand know of a seedling vendor in Minnesota.
These tree like deep, rich, moist, alluvial soils. They will tolerate some shade but full sun is preferred given proper soil conditions and consistent moisture. They won't be happy on droughty, sandy soils, at least not without supplemental moisture.
Last edited by MaineDesigner
on Fri May 28, 2010 8:20 am, edited 1 time in total.