It's important that air circulate. If you have a dome on it then you really have to keep the soil moisture just right or mold will grow.

They don't have to be in potting soil for the warm or cold moist periods, but they do have to be in contact with something moist not bare. If the seeds dry out during the process, the embryo will die. You can put the seeds (after soaking if soaking is recommended) into a tiny zip lock with moist sterile vermiculite or moist sterile sand. Depending on the size of your seed, a couple of teaspoons of moist product is enough. Seal and date. When they've gone through the periods of moist warm and/or moist cold, you can sow the contents of the bag, vermiculite and all.

morz8, Does that work with Stewartia spp.specifically? It seems very difficult to find that out.

Edit: As someone who is quite keen to grow Stewartia spp., and someone who grows plants from seed, please, let me say, I tried Stewartia ovata and S. pseudocamellia last year in soil. I did the warm stratification inside, and put them outside to cold stratify & germinate.

Unfortunately, we had a terrible spring that went from literal snow cover to 90 degrees F in just 2 or three weeks. All germination was terrible outside... Anyway, I got not one. That said, they may still germinate next year. From what I have read, that is not uncommon.

As far as media go, I have read that germination medium matters. Soil seems to work. Germination, however, is not great, and it is sporadic. Lately, I have decided to take a more scientific approach. Researches have used aerated soaks followed by stratifications and germinations in germination paper. So, I think I'll try that this year...

I think I'll just keep them in peat moss. As for temperature, is room temperature ideal or does it need to be on a heated mat on controlled temperature? For cold stratification, I think I will keep them in the fridge for couple months. Outdoor temps fluctuate too much.

It seems that success has been had at 25degC. You can read a scientific review from 2010 here https://www.extension.iastate.edu/vegetablelab/files/research/files/Stewartia%20review%20article-Ajay.pdf

Ok I guess I would need to have it on a heat pad then.. no way anywhere in My house would stay at 25 C. Thanks for the source, I will read that

The Taxa: S. koreana, S. malacodendron, S. monadelpha, S. ovata var. grandiflora, S. pseudocamellia, S. pseudocamellia 'Korean Splendor', S. rostrata, S. serrata and S. sinensis, have doubly dormant seeds. Warm stratification for 4 months (3 to 5 months) followed by cold stratification for 3 months prepares the seed for germination. If the warm stratification is started in October the seeds are ready for sowing in May. Even with those manipulations, germination is seldom uniform.

M. Dirr & C. Heuser jr.

Bill, what I'm reading now shows through experimentation that one can radically increase percentage germination by alternating warm and cold stratification after the first 4 mos of cold stratification. Of course, to know if germination has occurred one must stratify in some medium that allows one to clearly see radicle emergence.

There are generally more than one method in overcoming minimum dormancy requirement.

Ostrya virginiana, for instance is said to need warm stratification for 60 days followed by cold stratification for 4-5 months. I simply scarified the seeds in the Fall and after soaking placed them into cold stratification, frozen solid outside all winter. When I brought them into the house in the spring and they warmed, almost all the seed germinated and sprouted at the same time.

I put Taxus seed, notorious for germinating the second year, out for cold stratification for 4 months (Nov-Feb), brought them in March 1st and put them into warm stratification for 3 weeks. March 21, I put them back out in the freezing cold and left them outside to fend for themselves until spring. First week of July, some of the Taxus seed sprouted. A little late but still the same season, not two seasons.

I guess it’s always good to experiment as I can see from your successful taxus germination. I wanted to try taxus cuspidata from seed but after looking at the warm and cold stratification requirements I just gave up there.. but now I see yours and made me motivated! Maybe I should give it a try.

Anyways, I placed 17 Stewartia seeds in moist peat moss in a ziplock bag and stored it in my top kitchen counter. Hopefully temps are ideal enough.. I couldn’t find my heat pad.

Heruga, if they don't germinate this coming spring, and they aren't rotten, then they might still germinate (as long as they have remained moist the whole time) by cycling them through cold and warm stratification (possibly a few times).

Bill, it does not surprise me at all that you have developed better methods than Dirr and Heuser. I ordered "The Reference Manual of Woody Plant Propagation," and I will be returning it today.

The first two entries I could find (there was nothing on the third) were conjecture and wrong, respectively.

The wrong one Stewartia spp... The most recent/referenced/cited scientific study of Stewartia pseudocamellia seed viability that I have found (most people seem much more interested in problems associated with overwintering rooted cuttings) indicates that desiccation avoidance is crucial to seed viability. https://meridian.allenpress.com/jeh/article/17/1/44/79501/Germination-of-Stewartia-pseudocamellia-Seeds-is Dirr and Heuser literally tell people to dry out seed capsules before harvest--something counter-indicated!

I don't see anywhere in my book/version tells you to dry the seed.

Mine says this:

'The capsules are allowed to dry and the seeds will separate from the capsules with shaking'.

It then goes on to say:

'Stored seeds loses its viability quickly and should be sown or placed in pretreatment immediately'.

Was yours the 'Second Edition'?

Drying the capsules, I have read, is likely to result in desiccation of seeds. The authors suggest that the seeds be harvested immediately after the capsules are harvested and that the harvested seed be immediately stored in non-desiccating conditions. [If the seeds weren't so very expensive, I would conduct TZ tests on a hundred to see if any of the seeds I have are actually viable, because I am no longer convinced that they are.]

Edit: Do you know any expert Stewartia germinators? ...Also, yes, mine was the second edition from 2006.

I've never tried to grow Stewartia from seed so I have zero experience with that. But let me just say this, there are many levels of 'dry' and the same for 'humidity'. And you will never read a book and become an expert, that all comes from work experience, trial and error and finally success, hopefully.

Books can contain vague information, even errors but they also contain huge amounts of valuable information that can be used to further your success.

When I find information that appears contrary to my references, I do additional research or ask trusted friends, or come here and ask in the appropriate forums, to find out what the truth is.

Otherwise I just try the best I can and learn from that. In some cases, I'll do multiple methods in the same season, to see what works and what don't.

I've never regretted buying 'The Reference Manual of Woody Plant Propagation' from Dirr & Heuser jr. and I'll never use all the information contained but it's my go to when I want to do something new. :-)

A couple of links with information for Stewardia stratification and germination, in case you haven't already seen them (good read anyways). :-)

One is a technical publication: HERE:

The other is a Houzz discussion: HERE:

That first paper is a good review of literature, which is where I found references to both the Oleksak and Struve papers from 1999. :)

I would scarify the seed using fine >=600 grit emery paper, just enough to frost the sheen on the hard seed coat. Don't overdo it and break the seed coat.

Then do the 24 hr soak in water. ime: warm water works the best. I've put my seeds in a small jar and put the jar on a heat mat just to keep the water about 100df overnight and the following day.

Then all my seeds go into a cell or pot containing starting media. (I do this bc I think it's silly to sprout seed inside a baggie and then have to move tiny sprouted seeds into a cell with media).

Then everything goes out in the cold frame for ~4 months. I usually wait to do this until at least the end of October or start of November, so it's cold enough outside that the seed doesn't sprout (low 30's to ~40F but colder as winter goes on).

Everything I've done this way has germinated when brought into a ~75f room down my basement, anywhere from end of Feb to end of April and left to warm up for a few days. Your mileage may vary.

eta: After placing the seed into media, I stretch plastic, food grade wrap across the entire tray to prevent evaporation. The cold frame has never dried out during the winter but wrap is cheap and keeps the media moist.

Very good to know. I still have a lot to learn on this! Btw, where do you buy your cold frame? Or did you make it yourself? I want one myself but not really sure how it can work indoors when I don’t really have a spot where I can control temperatures in a certain room.

All im saying:

If you do all your seeds exactly the same and they fail, all will fail.

But if you divide them up and use 3 different methods. One method may do better than the others.

Or they may germinate at different times.

Better pics in this thread.

https://www.houzz.com/discussions/5405116/do-cold-frames-work-to-overwinter-trees-in-pots-in-zone-3