Can someone please explain what a ploid is? Does it have to do with what can cross with what, or can I cross any rose with any rose?

ploidy is a term for how many copies of basic chromosome number a plant has. So a haploid has a half normal, that is one of each of the seven basic chromosomes in rose, diploid is the usual pairs = 14 total. Triploid is 3 x 7 or 21, tetraploid is 4 x 7 = 28 and so on.

Many wild roses are diploids. Most fancy cultivated roses are tetraploids. Same story for daylilies, and many other flowers. Cultavated wheat is a hexaploid with three parents in its background, each of which is diploid.

I once taught a genetics class to high school teachers and they had do do something that they would present to their students. Two guys came on as the Lloyd ( or loid) twins, Dip and Hap. After seeing their show you’d never forget the terms.


I sense that you may be as new to this as I am. Recently, it was pointed out to me that if you click on “return to RHA forum” above and then enter your query into the “Search” engine you can tap into all kinds of info. In this case if you plug in “ploidy sterile” you’ll get a number of forum topics, one of the best of which for your purposes would be “roses are funny.” I am also sure that if you just stay on the line, one of the more knowledgeable members will be able to tell you more – but I am loving the search engine. I have plugged in the names one at a time of each of my roses and roses on my wish list and I am getting invaluable info. Hope this helps a little.

Bob in New Orleans

Thanks Larry for the information, and thanks to Robert for informing me about the search engine. Yeah, I’m new to all this and am finding it all incredibly interesting.

Greg, regarding your question about whether you can just cross any rose with any rose - Mr. Ralph Moore has said he doesn’t pay attention to the ploidy, but crosses whatever he wants to try to combine desirable traits. So I would say “go for it” with whatever you have an interest. If you are new to rose breeding though, you might want to try easier crosses to gain some early success!

Best wishes,

Jim Sproul


Jim is right. Get some of what I’ve seen referred to in the forums as “easy ladies” roses that set seed easily and have a high rate of germination. When you first start out you want to see some results and anything will do your first year. After that you can get picky – but there is nothing more exciting than when your first seedlings start popping up, knowing that each is unique – even if uniquely bad. And because they are unique you can give them to friends and name them after new babies, etc., and everyone loves having their own personal rose named after them, even if its not an ARS winner.