rainbow knockout fertility

Last fall I managed to collect some O.P. hips on RKO. So this year I tried it as a pollen donor very early in season when it was the only non-species in bloom. I continued to collect pollen and use it right up to the present.

I was pleasantly surprised that with Carefree Copper as female parent, I got 1/4 of crosses to set hips with RKO pollen. But what I find remarkable is that New Dawn, which usually gives me about a 10 % take, has 80 % or so of all RKO pollinations being successful. Other crosses attempted about the same time have the usual dismal hip set.

I realize that RKO has its limitations, but it might introduce floriferousness at least, and maybe petal longevity and disease resistance.

Has anyone else used it? Did anything interesting come from it?

Hi Larry!

That is great!! I have been using RKO. It seems to be the most fertile of the Knock Outs for me (both as a femail and male). Many of the seedlings shed their petals better than RKO which is nice. I have been conscious to try to mate it with other parents that have high mildew resistance. The seedlings tend to be black spot resistant which is great and many are well branched. RKO gets spot anthracnose very bad for us here and defoliates as if it has black spot. The susceptibility seems to have come through to many of the seedlings. I have not used it this year and my hope is to use some of the seedlings and hopefully retain good black spot resistance and see if I can draw out better spot anthracnose resistance in the next generation. The same seems true for ‘Yellow Submarine’ with it being very black spot resistant, but highly susceptible to spot anthracnose. Fortunately, spot anthracnose is not as common as black spot and tends to build in larger gardens with lots of roses.

I used it on rugosas 2 years ago. They haven’t flowered yet so it’s too early to tell. But the seedlings survived winter outdoors in pots, so hardiness wasn’t compromised. Has anyone used it as a seed parent? Its always in bloom.

Thanks David for your observations. Spot anthracnose is really rare here. At end of season New Dawn has something that may be that, though it looks more like a hypersensitive response. The spots are minute. I don’t see any sign of it on RKO, which grows on campus alongside a parking lot, not in my yard.

Most years we don’t see much mildew, but I have a ton of mildewy seedlings now. Seems that Country Dancer- see another thread- gives it in abundance to its O.P. seedlings. I have over 1000 now, and seems all are covered with the stuff. Not a trace of mildew on RKO itself, nor on pink KO, KO or double KO anywhere I see them.

So far from over 100 RKO seeds collected last Nov., I have 2 germinations. Not a good sign in my opinion. I notice that most hips are set near the ground and under the bush and were probably amongst the earliest flowers on it. Basically nothing set since early May. Last fall there appeared to be immature hips from the fall season. I think it may be a temperature sensitive seed parent. I observed a similar (very sparse) hip distribution on KO. Wonder what it means.

RKO was chosen because the yellow center at least suggests that it will allow yellow from another source. And the weak pink suggests it ought not to be too domineering in that department.