This is the plant I'm talking about. Is this vinca? Thanks.

The only way to be sure you get the same color is to propagate vegetatively. You can dig up the entire plant, prune it, root the parts you prune off and keep both the cuttings and the original plant. I tried a couple of years ago and it did not do well for me indoors, but there's an entry in my houseplant book for this plant so some people must manage it.

Catharanthus seeds are widely available from all the seed houses by late winter, if you want to grow some yourself. Search for them under their real name, Catharanthus roseus.

I'd love for you to collect seed pods and see what happens, but I strongly suspect that the results will be highly variable. Inside environments can be difficult without very good auxiliary lighting, I would think. They are such lovers of heat and light.

Not a true annual, but not very hardy. Most sources list it as Z9/10+.

its very hard to over winter things in the house.. the colder your zone ... it has a lot to do with forced air furnace.. aka ambient humidity ... and lack of proper light ...

if you had a light stand ... and learned about propagation... you can probably do it easily .... rooting and rerooting plants all winter long.. culminating in late march.. with a nice number of plants ... but unless you are willing to go that far.. i wont waste my time describing such ... new post with good title.. will get you that ...

take the latin name.. add PROPAGATION... and google away.. to find out how to do it ...

genetics is kinda cool.. when trying to grow self collected seed... as you found.. there is little predictability .. and many of us.. would like the challenge.. and the bizarre results ... not really considering off color to be a failure ...

but to insure what you want.. you have to usually buy the seed pack .. which is not really that much of an investment.. to insure the result you want ... but then growing a flat of plants indoors in late winter.. can run you right back into the problems mentioned above.. humidity and light ...

ken

The pessimism of previous failures doesn't help, but their anecdotes can help to examine what was done & make sure something is different in a subsequent attempt, if there are other options. Success stories are much more helpful, in both theory & practice. Something as simple as a different room/window, or different watering practices can sometimes be all that's needed. Anything that's not a true annual is fodder for consideration about overwintering. Whether or not it goes well, there are no guarantees.

Thanks. I may try the collect seeds just for fun!! I've got a nice room that has a south window and I've been lucky to have started several kinds of seed. So what have I got to loose! Have fun and learn something too!

That's the spirit! I've never regretted trying a thing that failed, but have regretted not trying at all.

What you have to lose is pure white flowers if that is what you want. Have fun with growing collected seed if you want, but if you want a very specific item and will be disappointed in anything other than that, buy the seed for it. Too much hassle to take cuttings of commonly-available annuals and grow in the house, and if you grow under lights all winter, that will cost you more in electricity than a packet of seeds.

You should be able to buy the seed (Park Seed has some) just google white vinca seeds. If you don't mind experimenting, you can collect seed. But if you really want white next year, just order the seed from Parks or another reputable source and start them early next spring. Vinca is a very warm season annual and might be difficult to over winter. It does not like the cold. It also rots rather easily, but it grows well from seed so give it a shot.