I gut wings off with scissors and sowed them when fresh on top of prepared soilbed and put about 10...15mm of 3...4mm gravel on top. Because of squirrels I also put steel mesh over the bed. In spring I just took the mesh off which neatly cleaned the bed of some fallen leaves. Last winter we had only few inches of icy snow when temperature dropped to -25C. About 1/3 of seeds started to grow so I would say A. pseudosieboldianum is hardy to at least Zone 5 without any special protection.

They survive in Arboretum Mustila Finland where temperature has been as low as -40C which equals -40F which is Zone 3 minimum. However those trees are from seeds which were collected from harsh mountains in Asia.

What little information I have seen on the species was from the Morton Arbor., 2006 IIPS Proceedings.....poor germination. There was another article back in 1993 IPPS Proceedings on different Acer species also....there always seems to be a trick, finding it is the hard part:-)))).....