All things are possible when it comes to plant pollination schemes, I don't think anyone can ever say "never" :-) However, normally plants do not cross-pollinate outside of their species (interspecific crossing). I think you would be safe to plant the bipinnatus cosmos near the sulphureus cosmos. Just my opinion of course.

Art

i always presumed .... once given.. a latin plant name is next to God.. unquestionable ...

and in the years i have been hanging out in the conifer forum ... i am surprised how many discussions there are on renaming various plants.. once they actually cone ... and as a tree.. that is 10 to 20 years later ... [that means changing the second latin name]

i know nothing about cosmo ID ... just a random.. early morning thought ...

and the easy solution ... think outside your box of 2 spots ... think 3 ... two spots isolated.. for seed collection of the pure strain ... and one in the middle with the mix ... to SEE WHAT HAPPENS ...

but i doubt it matters.. short of a few hundred acres.. you are presuming bees have a limited range.. and i am pretty sure.. they cover huge areas ... as in miles ... so no matter what you do.. the bees will most likely defeat your purpose of isolation ...

ken

I would want them to cross pollinate. It would widen the color range of each species. And perhaps unlock some other nice characteristics as well.

One of the most interesting zinnia strains are the Whirligigs and the similar Swirls, and they are a result of crosses between the two zinnia species, Zinnia violacea (elegans) and Zinnia haageana.

Cosmos have already shown some interesting variations, like the Sea Shells and the double cosmos. And some cosmos strains can grow very tall. Hybridizing cosmos could be a good thing. My hobby is zinnias, and I hope to develop a strain of zinnias with a flower form like the Sea Shells cosmos. I have already made some progress in that direction.

But I have a long way to go before my zinnias can look like the Sea Shells cosmos.

ZM

tj

its all greek to me.. or i suppose.. latin ...

so we set up a menage et trois ... with the third party .. and repeated plant fornication over the generations.. back and forth.. until zenman comes up with his dream plant. . sounds simple enough.. given a decade or two..

BTW jungle.. my apologies .. lol ..

do you know how to protect a given flower .. to insure the seed remains what you wish??? .. some use nylons.. paper bags etc ... you have to cover the flower.. when its able to 'take' viable pollen.. just long enough.. to protect it from those darn bees making crosses on them .. and then you would harvest just the flowers you protected ... though it might be easier.. to just buy a new pack of seeds every few years ... the real trick is to know when the given bloom will be fertile.. and if that is the crack of dawn .. well.. some of us forget to run out there and basically.. put the condom on.. the night before.. or that early morning ...

and it is usually at this pint.. that i declare one of two things ...

1--- i love to breed my own unique cultivars.. lol ..

or

b--- its part of my master plan on developing something new ...

either involves having a good excuse for doing little or nothing .. other than collecting ripe seed in fall. and spreading them in spring.. lol ..

ken

There are several techniques for overcoming barriers to hybrid crosses, but most of them, if not all of them, are beyond the scope of amateur plant breeding.

If there was an economic market for extending the color range of the Sea Shells cosmos to include the yellows, oranges, red-oranges, and scarlets, then it could be done. But doing it would require an outlay of money, which might not be recouped with a seed-propagated ornamental such as Cosmos.

One edited-in-comment I would like to add (i-Village, I really appreciate being able to do this): I would like to point out that amateurs can approach a plant breeding project without proving its profitability to a management review. I do my zinnia breeding purely for fun and enjoyment, and since it is a hobby, I spend money on it rather than make money from it. So I am free to tackle any zinnia breeding project that appeals to me, within reason. And an amateur cosmos breeder would also enjoy that freedom.

But the answer to Jungle's original question is, go ahead and plant your cosmos where you want, with no fear of them crossing and thwarting your plans to save seeds.

ZM

Gaaa, I confused the OP with another poster and thought the OP wanted to cross.

Yes, jungle, it should be safe to plant them together.

tj