Kris,
I didn't have any problems with germination of the seeds...and, they didn't get any "special treatment," either. Just my $.02!

Emily

It is easy, but a little slower to germinate than the other popular annual, coccinea, and like coccinea you surface sow. Just remember it gets big, up to six feet and appreciates decent soil and regular water.

Collecting the seed in hot, humid problems is more of a problem, as is getting good cutting material under those conditions. Plants, especially seedlings, wintered over in the greenhouse definitely are easier for me to do. As soon as it gets hot for me, I can forget about cuttings, or even collecting seed. For me, it looks like the calyxes holding seed fall off soon after ripening.

That is exactly what happens. And then the next spring hundreds of seedlings appear. I wonder if this might become invasive in some areas. Any alien plant as happy as subrotunda should at least be a cause for concern.

Wardda's concerns are spot on about the possible invasive qualities. I double that it will become a pest in many areas because of heat stress. Time will tell.

I've found that the axillary growth of subrotunda can root easily, so I will have some plants to send to my family in Massachusetts to see if they can collect seed for me.

Richard, you can ask me about that. We've been growing a 20 X 10 patch of it for a couple of years now. A woman who has been very helpful in the gardens the past few years collected seed for us late year and we intend to continue the practice. On such a big patch one collection effort can usually produce hundreds if not thousands of seed. The plant has proved to be extremely valuable to hummingbird gardeners.

If you are interested, I also have the Pink Dreamsicle type coccinea. I grew them out as a seed crop for members of the other hummingbird forum last year and even after filling about 25 requests I still have possibly several hundred seeds. As you probably know Dreamsicle grows quite tall, is the last of the coccinea types I've tried to bloom, and has a bad habit of closing its flowers on hot afternoons. It looks like a giant Coral Nymph.

I sowed my salvia subrotunda outside in containers in March last year and had very good germination. (winter sowing method)

I didn't collect any seed last year because everyone said there would be lots of volunteers. I also get plenty of volunteers from coccinea. I don't have any volunteers from either of those yet this spring but I'm sure I will.
Can it become truly invasive even where it's just an annual?
I wonder if birds carry the seeds off.
Coccinea flowered better for me by the way. If I had to choose between the two I would keep that one.

Annuals and biennials are the worst offenders as invasives. Par of their survival method is to generate lots of easily germinated seed.

I have wintersowed them and I have germinated them inside and they seem to take a little longer than say coccinia which germs the easiest. Mine became the largest plant I have maybe 4ft but I had a bout with aphids early on which the ladybug took care of for me.