Heruga, this article says that the majority of hinoki seeds are always unviable, and I don't think the water test works with them, but most of them probably are not viable. I don't think you want to buy a MRI machine to check them lol.🤔😆

https://www.researchgate.net/publication/278684200_Determination_of_Seed_Soundness_in_Conifers_Cryptomeria_japonica_and_Chamaecyparis_obtusa_Using_Narrow-Multiband_Spectral_Imaging_in_the_Short-Wavelength_Infrared_Range

a couple months ago I experimented with Cedrus deodara seeds. I let them soak for 24 hours then separated the floaters from the sinkers and placed each in their own bag with some sterile damp 50/50 peet moss and perlite. They germinated quickly. I would say that probably 80% of the sinking seeds were viable and maybe 5% of the floating seeds were. Cedrus deodara makes a significantly larger seed than C. Obtusa so if some deodara float and are viable I would think its reasonable to assume viable obtusa could float. I think the floating test shouldn’t really apply to tiny seeds, that’s just my opinion though.

Interesting. I don’t remember seeing too many seedlings of hinoki or cryptomeria out of all times Ive been to their forests in Japan. I guess human intervention is the best way to save these species?

Well not all hope is lost then. But It’s been a week since I sowed them and nothing so far. Im having my doubts

One week?? Patience, grasshopper :-) Once they have gone through a suitable stratification process, it can take anywhere from 3 months to 2 years for germination. They aren't carrots :-)

According to this site;

Chameacyparis obtusa germination could take more than a few days.

{quote} 'Watch for germination in three months, but don't be surprised if many of the seeds take up to two years to sprout. '

Couldn't find anything on the Larix.

Oh and the float sink test is totally unreliable, or may be perfectly reliable, depending on a lot of things.

From my experience this winter trying various spruce and fir:

The smaller seeds are more likely to sink after 24 hours, and smaller seeds that float are less likely to germinate. Larger seeds are less likely to sink, but a significant portion of the floaters will germinate. I don't have hard numbers because I sowed many more floaters per cell (anticipating lower germination rates). I would say that bottom line: if you've got space, sow the floaters, especially if it's rare/valuable seed.

My pinus thunbergii seeds germinated in 3 days last year.

Many of the Tsuga canadensis seeds that floated for me last year, germinated just fine.

How long did it take for you to germinate after sowing?

Also, I used my sand:perlite mix that I used for my cuttings to sow the seeds in just because I had a lot leftover and didn’t feel like wasting it. Do you think sand is going to cause issues with the seedlings? Should I have gone with the standard peat:perlite?

Pinus thunbergii is not the same as Chamaecyparis obtusa. Some seeds just take longer to germinate than others. Japanese black pine is a particularly easy and fast conifer to grow from seed.

About 3 days under ideal conditions.

But it's different for different species of trees. My Jack pine (Pinus banksiana) seed says:

' Jack pine seed usually germinates within 15 to 60 days under favorable conditions, but some seeds require more than 100 days to germinate. '

So it's good to know what the requirements for your particular seed is, otherwise you might think they've failed and abandon them prematurely.

So I bought chamaecyparis obtusa seeds from sheffields this time and I soaked them in water last night. As of now 20 hours later none sunk. So I guess they normally don’t sink because of their flat seed shape and how light it is. But seed crop is from 2015. Is that likely too old for any viability? Weird thing was though, there were some fragments of its hinoki foliage in it which were still partially green.. I wonder how they conserve it

They freeze all their seeds for storage.

My Picea mariana seeds from them were from 2006, they all sprouted.