Different ploidy in making crosses

Are there differences in success rates when using a diploid as a seed parent and say a tetraploid as the pollen parent and visa versa?

I’ve been reading threads with some complications with using triploids, but have not seen anything using 2 x 4 or a 4 x 2.



Conventional breeding wisdom says to put the tetraploid pollen on the diploid. Just on a whim, I tried using Therese Bugnet pollen (diploid) on Champlain (tetraploid) last year and none of the attempts took. I also put Morden Centennial OP pollen (tetraploid) on TB and those attempts failed too. So maybe Therese Bugnet isn

Jeff, selecting an easy seed parent of any ploidy is key.

Some seed parents seem to accept any pollen.

Finding what works for you while keeping in mind your ultimate goals should make the selection process easier.

I’ve done crosses of all ploidy combinations. They generally all work to some degree. As long as the seed parent is willing you should have some success as long as you keep in mind that mixing ploidy generally results in lower fertility and in some rarer cases perhaps sterility.

I think Robert put his finger right on it. Roses don’t pay a lot of attention to ploidy issues. Sterility/fertility can be an issue with roses regardless of ploidy, so don’t spend too much time worrying about matching plants according to ploidy.

Some things I know about roses based on personal experience:

-Many triploids are extremely fertile. ‘Out of Yesteryear’ is a triploid and it has excellent fertility. ‘Buff Beauty’ is similarly fertile.

-Sometimes balanced diploids and tetraploids are highly infertile. The mechanism that determines fertility appears to have more to do with how dissimilar the parents are and is not so much a function of ploidy. I have some diploid and tetraploid seedlings that have turned out to be totally sterile, so ploidy isn’t the only issue controlling fertility.

-Selecting a highly fertile seed parent, regardless of ploidy, is by far more important than matching gene counts. As Robert said, some roses will accept pollen from anything and give you loads of seedlings. Such roses are a huge asset in any breeding program. In my experience there aren’t a whole lot of these hybrids available to us. Eventually you will find seedlings among your work that provide this opportunity: make good use of them!

-Make any and all combinations you want to make and measure their success by the results you get, rather than NOT making the crosses because you are concerned about compatibility issues.

I concur with Paul, achieving one’s goals in breeding roses often involves taking detours.

I think it’s important to note that while rose hybridizers are judged by their successes, they are not judged by those crosses they attempted.

I know people will wonder why I did this or that in the future but trust me, it’s not because I didn’t try other things. I HAVE!!

It’s too bad there isn’t a database of attempted pairings.

That type of information could save us all a great deal of time and frustration.

Thanks for the input gentlemen. I’m still chasing a couple of long term goals and began wondering about other possibilities.

So many roses and so little time!!


Be prepared to shift directions at every step, because you WILL find yourself blocked again and again by sterility or other problems. Its always a good idea to have multiple strategies for getting where you want to go, and to identify the best seed producers as early in the game as you can, and concentrate on using these.

Another point: even the very difficult combinations may deserve perseverance while failing as were the first foetida hybrids or Itoh peonies.

Also repeating again crosses that yelded sterile offsprings you may get the fertility to go further.

When doing species crosses one often fails with nine mothers out of ten.

Excellent points by all! I can probably hardly remember all the failed (and poor) crosses I’ve tried over the years.

I used to worry about ploidy - not so much any more.

And some of the more difficult crosses can be most worth trying. I haven’t been able to get any seeds from multiple attempts to repeat my cross of ‘Fragrant Cloud’ with the local clone of Rosa carolina, but I’m very glad I did try and have success that one time. It’s been a seedling to play around with.

Like Paul and Robert said, be prepared to change strategies midstream. It’s all part of the fun.

Take care, Tom

What Pierre says is true. Some years certain things work and other years they don’t.

It’s worth repeating even difficult crosses if you have the time, energy and inclination. It’s hard to make sense of it but at least there is hope.

This old saying comes to mind.

“Nothing ventured. Nothing gained.”

Tom, I’m am in awe of some of your hybrids. You’ve done some amazing groundbreaking work. Yours are the type of breakthrough hybrids that can bring real change.

All we have to do is bring them forward.

This brings something else to mind. When possible I try to use the work of others. If we don’t seize the opportunity to bring the innovative work of others forward, those hybrids, the work of that hybridizer, those opportunities for exploitation, can be quickly lost forever.

The work of John James among others comes to mind.

That’s why I have sought to use the work of lesser known hybridizers. If we don’t use them who will?

Even when using the work of well known hybridizers I prefer the challenge of taking the less traveled road.

It’s less predictable and often less productive but to mind ultimately more gratifying to try something different.

It rewarding to give others the chance to shine and at least take their vision another step or two.

Robert I looked up the work of John James. He had some amazing crosses. So is all his work lost completely. Who else is in that list of people we lost their work.

Adam, HMF has many examples of breeders who’s species work seems to have been lost.

Pick any species and start doing a search for descendants.

Many have yet to be explored but a surprising number of hybrids were accomplished and recorded but were carried no further.

On some level it’s up to us as to make sure our work doesn’t result in a dead end. If we don’t make sure these things get into the hands of others it can easily happen.

As I remember awhile back someone here tried contacting the James family but they were of little help.

Too often families and loved ones don’t have any idea what’s in a hybridizer’s collection. Once we’re gone all bets are off.

It’s very easy to lose focus and begin exploring too many options when working with species.

I’m there already. I’ve too many options. I wish I could explore them all.

I try to share things but even giving stuff away gets expensive. I’ve still got a couple of kids at home and one out of the house and trying to be independent. These are rough times for many and breeding roses is largely a luxury for those of us with the time space and energy.

It’s critical that we share when and while we can.

Robert wrote: “Tom, I’m am in awe of some of your hybrids. You’ve done some amazing groundbreaking work. Yours are the type of breakthrough hybrids that can bring real change.”

Well, thank you Robert. You’ve got some pretty cool stuff too. I’ve been focused mostly on making rose species crosses since the mid 80’s, so as you’d expect probably, there have been a large number of failed crosses, runty seedlings, etc. to go along with those few good ones [the ones that make me smile in appreciation]. My goal all along has been to try to incorporate the underutilized species - and there are so many of these. With full time work and newly expanded family, I haven’t gotten to do as much hybridizing lately. But, I still got a chance to play around with Rosa glutinosa this season. And I’ve got some two-year-old, OP Rosa laevigata seeds germinating in the basement. That’s another species, whose pollen I’ve been throwing around this season. The North American species have so much to offer too. Eventually I’m going to get around to doing much more with these, I hope.

Which reminds me - I know exactly what you mean about hybridizer’s work being lost. I had done searches on HelpMeFind and got acquainted with Lou Stoddard’s work with the native species. Lou sounded like someone I’d enjoy chatting with. So I tried to find him, but sadly he had already passed away. And to make the sad situation even more sad, I talked with his family and I don’t think anyone has any of his hybrids.

So as you mention, it is a good idea to share when and while we can. I’m terrible at propagating most stuff, but still try to share what I can, when I can. I’ve tried to send out a few rooted cuttings or budwood of most of the better hybrids I’ve grown. Actually this forum has been great in this respect - I don’t know how else I’d have found people who’d appreciate my hybrids. And it would give me a great deal of enjoyment to see what other people could get by working with my hybrids. If only I had enough money, spare time and propagation skills.

Tom, I really look forward to seeing what you come up with next.

I’m especially interested in laevigata. Most of the laevigata descendants I have here look atypical. Some I suspect the result of apomixis as a few of them repeat and show no signs of laevigata lineage. They do not look like selfed seedlings which is one of the reasons I find them confusing.

A couple do not repeat and show no sign of laevigata lineage. Phenotype could be masked. I hope they eventually flower which should help tell the tale.

I’m sorry to hear about Lou Stoddard. It’s a pity his work is lost. We have to make a concerted effort to share while we can. He had some great stuff.

I try to use my materials for a few seasons and then spread them around. Most are not commercial looking which some not doubt find intimidating.

All we can do is try.