I wasn't sure if presoaking had an advantage as I saw different information on websites. On February 29th, I soaked 2 seeds of the white variety for a couple of hours and then planted them. I also planted 2 of the white variety unsoaked seeds in another cup to see if the presoak had any advantage in germination.

Both cups showed germination in a week(on heat mat), but the one that was presoaked both seeds germinated whereas the unsoaked ones only 1, as far as I can tell, has germinated.

Of course not scientific as all seeds react differently, but thought to share the results. I'll post pics once they get bigger.
I would say it really doesn't matter whether to soak or not the seeds before planting but definitely doesn't hurt.

thanks for the info.. would love to see photos!!

Here is a pic I took this morning. These seeds came from the same white C&S packet. Notice how dark the one stem is that has the leaf already emerged from the seed shell versus the other one that has a very green stem and the leaf is still emerging from the seed shell.
I'm not sure if this is typical with Cup and Saucer to have the vine different in color. If you click on the pic you will get a larger view.

wish I knew

So cute!

Thanks for sharing your findings, Julia!

It will be a long wait to see if they do bloom white or not but odd the stems are so different in color. I was trying to google images of the white ones to see if the stem color is different. I know the purple ones appear to have darker stems from the images I'm seeing online.

Time will tell.

I'd just about bet you have a purple one in with your white seeds! The purple ones definitely have a purple cast to both the stems, leaves and tendrils, while the white ones are more of a yellow-ish green on all parts of the plant.

In the cup pictured above (presoaked seeds), they are getting the second set of leaves and still look different as far as stem color. The other cup,(didn't presoak) only one seed grew. Maybe there is something to presoaking the seeds.

I plan to start more in a few days along with moonflower seeds.

I'm thinking you're right about the presoaking. The ones I started haven't done much, so I'm trying a few more, soaking them first. Sigh, I'm running out of seeds, tho. Darn, but I wish I'd thought to take cuttings!

Are you putting them on a heat mat?

Oh, yes!

For the record, the second batch, that I pre-soaked, did MUCH better! Greater germination rate, and faster germination. AND I think I was planting them too deep, as well. The package said 1/2 inch, but these last ones I just pushed in on edge so they were just below the surface. So thanks, Julia, for starting this thread and mentioning all this stuff!

Glad to hear your getting better germination.

The trial (2 cups), are still going. The ones I presoaked are growing fast but the ones (only 1 germinated) I didn't presoak are very slow. It better get consistently warm here soon as I'm not sure how much longer I can keep the one cup going. It is growing by leaps and with nothing to attach itself to, it keeps leaning towards the bars of the shelving frame to wrap itself to.
At least I know I can start another batch soon which will be transplanted outdoors in May.

These are mine. I soaked the seeds for 4 hours. I had 4 white none sprouted.
These are all purple.

Still 1 or 2 pushing up.

Those look good and the purple looks like one of the whites I have that I thought the stem color was rather dark for white. I think there is something odd with the whites not doing well.

All of mine that I started are dying. I think being in the cups so long is not a good thing. I'll start another batch next week so they'll be ready by Mid May to start hardening off and then plant them end of May. I'm disappointed but learning.

I'm done. Will have to do with purple. The 4 seeds was all I had. I like purple anyway. Good luck

They really don't like being transplanted. Mine are to the point where it's probably time to move them into coffee cans so I won't have to disturb them again. And yeah, the white ones are pretty persnickety. I ended up with 2 of each. GOT to remember to take cuttings this year, 'cause I'm out of seeds! Have you had any luck collecting seeds off them?

I never thought about that. Good idea.

Which "that"?

I'm brand new to this site, so my info is probably too late for 2012, but perhaps useful for future years.

I started Cobaea scandens 'Alba' seeds (purchased from HPS - 100 seeds/pkt, cheapest I found) on Feb 12, 2012. 2 unsoaked seeds in each 1-1/2"x2-1/2" 6-pack cell = 12, planted on edge just below soil surface. I also soaked 12 seeds overnight and planted them on Feb 13, 2012 in the same way as unsoaked. Both were under lights and inside sealed poly produce bags but not on heat mats. Both began germination on 02/20/12 and completed on 02/22/12 with 100% germination. For these, it appears that soaking only made a day difference (not enough to deal with that slimy seed coat soaking gives). Poly bags removed after germination completed of course.

BTW I've tried these before from other seed sources w/ MUCH poorer germination - it seems that seed source makes a big difference for these plants.

After thinning to 1 per cell, I potted them up on 03/12/12 (actually could have been at least a week earlier) in 4-1/2" sq pots that were 5" deep. They remained in those pots outside (brought in if nights cool) in full sun until our plant sale on 4/14/12 - bamboo staked up, fairly root bound and about 3' tall. Kept one "runt" for myself as a test (they're uncommon here - don't know if they're a cool season plant or if they can handle our heat and humidity) but the plant established very quickly after transplanting even being quite rootbound.

I'd love to know if anyone in the Deep South (hot, steamy) has had success with these.

Monica