AlaskanAmazon - Hi! I have black Tacca. The seeds take quite some time to germinate. Make sure the soil is kept warm and moist. I'm in Florida, the exact opposite corner of the country from your WA home. My Tacca sits in morning sun on my pool deck/lanai. I never thought the seeds from the first flowers I had would ever take, but I kept them in the same pot as the mother plant, burried them in the moist soil. Finally, about 3-4 mos and I got new babies. Once a plant is established, it will send out suckers bulbettes from the mother plant. I just removed about 6 new babies this week and potted them up. Good luck-let us know how it goes!

My experience:
longest-12 months
shortest-6 months and like Cindee said, keep soil warm and moist.
T