When do you give up on an apparently infertile cross?

Assuming you have mature plants, a great climate for the roses involved and all other things being equal, how many times do you try a particular cross before you move on to more productive things?

For the most wanted more difficult crosses such as macrophylla clinophylla or laevigata I rely on mixed pollen (adding species pollen to an easy to sort compatible “mentor pollen”). And keep trying for years. No end.

With laevigata I succeeded after some ten years.

And will continue as I am not happy enough with actual results.

The answer depends on how your brain is wired. I personally don’t mind trying 50 or so pollinations every year to see what comes of it. If that’s all in one week, it’s no big deal, timewise. I guess I’d make excuses for poor pollen, poor weather etc for several years. I know that I have records of showing 200 failures with one pollen donor on one recipient, in one season. But usually I had some % successes to go with it, though they maybe didn’t germinate a single seed. But I do test the pollen donor on other recipients and the recipient with other donors to check on feasibility too.

In a science lab we regularly have failure rates like that when trying to do something new or hard. So I guess we get used to it.

Best example, pollinating Austrian Copper with Carefree Beauty pollen, I got exactly one seedling a pink double that died after a couple blooms. That was from who knows how many attempts. A lot. But the cross the other way was highly fertile, producing lots of hips and seeds, a decent fraction of which germinated. In 1987 I had 7 hips with 35 seeds, got 24 plants. the next year I had 52 hips, 210 seeds, 70 plants that lived a full season, mostly to be culled (but 3/4 bloomed 1st yr, so maybe were not hybrids.) the next year I had about 1/3 of pollinations take, got 51 hips, 182 seeds, 50 % germ and half of those bloomed 1st yr.

Austrian copper set seed on some other parents including High Noon and offspring of Carefree Beauty. My most interesting seedling of course didn’t bloom the 1st yr.

Twice, in different years. I have no patience for crosses that don’t want to work. I look for a different way to do the same thing, if possible.

There are so many directions in which to devote time, I don’t have much patience either. I try to work with mostly highly fertile seed parents. If the pollen “doesn’t work” in the first year, I may try one more time, or do as Pierre does, mix it with fertile pollen of a very different variety that I am also interested in crossing. That way the crosses aren’t wasted, and you can pretty much tell whether a seedling is from the lower fertility pollen or not.

I also tend to think that where there may be compatibility issues, that the other more fertile pollen may help to make the seed parent more receptive to the lesser fertile pollen.

Jim Sproul

Count me among those that moves on quickly.

Even when a cross works there are often health and or vitality problems. I’ve culled a lot of seedlings this season.

In my opinion it’s best to concentrate of what works. I follow fertility.

One “trick” to try is to do the cross both early in the season and late in the season if the mother rose has 2 periods of bloom.

My patience is probably slimmer than most. I think one could argue any direction possible, but I think it comes down to personal preference and attitude. I do admire those that can stick something out with undying devotion to repetition.

I have done what Pierre does as well. If Ive noticed something will set OP but not intentional crosses, I have blasted it with selected mixed pollen. It works on occasion.

I still want to try nuking one type of pollen that I know will work to render it infertile so that I can mix it with fertile pollen that usually wouldn’t work. Hybridizing season is so short that I always forget to try it out.