Distinguishing Sundial lupine and Western lupine

We have had lupine in our gardens for 10-15 years - in part because it's a showy, attractive plant, but also because it is the host plant for the caterpillars of the endangered Karner Blue butterfly.  But I didn't know until recently that there are two types of lupine.  Lupinus perennis ("Sundial lupine") is native to the eastern and midwestern U.S., while Lupinus polyphyllus ("Western lupine") is native in the western states.  The video embedded above explains the morphological differences between the two lupines [TLDR: the Western lupine has 11-17 leaflets on the palmate leaf, while the Sundial has 5-11].

The distinction is important because only Lupinus perennis ("Sundial lupine") will support the Karner Blues.  If Karner Blues lay their eggs on Western lupines, the cats will die.  See this excellent page from the recent Prairie Moon Nursery catalogue:

Western lupine has been introduced in the east because it is somewhat more showy, but it should not be encouraged, for the sake of the Karner Blues.

See also my 2015 post Pursuing the "Karner Blue" butterfly.