Yep, me again. For the Robinia, it's a different problem. For this seed, there is a thick outer coating, which muct be broken down. Some folks suggest rubbing on sandpaper, but I don't like this method, it's too easy to damage the precious seed. The way i would suggest is to soak the seeds in hot water (not boiling) and keep pouring it out when it has cooled and replace with hot agaon until three quarters of the seeds have started to swell up indicating that the coating has started to break down and water is being absorbed. ( After a few changes of water, you may need to just leave them to soak for 5-10 hours). When they have 'had a drink', sow them in a little sharp sand/peat mix and keep them at around 18 - 20 C and cross your fingers. These are fabulous trees, if you get lots to germinate, you'll be able to sell your spares on eBay no problem!!!