seed

I germinated them at 70F in common potting soil, in a pot that was covered in a bag to maintain humidity. I probably sowed 30 seeds in the same pot and only one germinated (I don't remember how long it took). After germination it is essential that you maintain even moisture. I did that by keeping the pot covered with a plastic bag.

They are not good seeds to germinate. But the plant is worth it.

I've always gotten very good germination rates ( >90%? ). I do it pretty much the same way. For me, these are some of the easiest seeds to germinate I've seen.

Need stratification.

Lots of info if do search with
"germination of katsura tree seed site:edu" - but no quotes

Here is a link that might be useful: germination of katsura tree seed site:edu

"Need stratification."

Mine haven't! And, almost all sources say no pretreatment (which would include stratification) is needed. Stratification won't hurt, but I doubt it going to make a huge amount of difference. If the seeds aren't germinating, it sounds like there may be some problem somewhere (bad seeds, improper moisture, or something).

Apparently they sprout fine without stratification, but they seem to do okay with it also. I winter sowed 12 seeds in January that were collected at the Arnold Arboretum last fall. According to my records the first sprouted on April 5th. I got 2 seedlings last Spring, and they grew pretty quickly the first year - they are almost 2 feet tall. I'm not sure about this species hardiness but they're over-wintering in the garage with the rest of the babies and tender plants (Salvia B&B) anyway.

Here's a pic of the baby seedlings, May 11th -

I collected a paper lunch sack full of Cercidiphyllum magnificum seeds. Then I made a couple of raised beds, and then sowed the seeds right away that Fall. Springtime came and the seed bed looked like I had sown grass. I eventually sold over a thousand of them. One order was for 600.
I haven't had to germinate any since because I get a few volunteers every year from the ones I have left.
Mike