Sorry this took so long, Angie! I have been having a horrible time finding info on germinating Lupinus arboreus seeds. So far, this has been the only thing of some use:

"...the Lupinus genus does have germination issues because of the hard, virtually impermeable, seed coat. The seeds may have to be scarified to successfully germinate. You may also need to inoculate the seeds with Rhizobium bacteria prior to sowing them."

from "Mr. Smarty Plants", of the Ladybird Johnson Wildflower Center.

Aha! A bit more info:

"[for] Lupinus arboreus, littoralis, podophyllus, polyphyllus, russel hybrids, sericeus, and texensis , Pour hot water over seeds, let soak 1-3 days until swelling noticeable. Sow at 20ºC (68ºF) for germination in more than two weeks"

From the Tom Clothier Seed Germination Database.

Hope this helps!