Back in January of 2015 I ordered 60 amorphophallus titanum (arum titan) seeds off eBay, and have since been selling all of them except for one for myself to keep. These are grown in pro-mix HP potting mix with mushroom compost mixed in to hold the soil together better. Once they had leaves completely unfolded, I started fertilizing them with water soluble miracle gro. I also added in some epsom salts, myccorhizae, and azomite to make sure they have the nutrients they need. Almost all of them came up, some sooner than others. It has been an entire year, and now almost all of these plants are in the hands of others.
They took 2-3 weeks to start sprouting roots and nubs.