... growing and hybridizing all kinds of plants in zone 6b Maryland since the 1980's.

Saturday, November 3, 2012

Rosa rugosa X xanthina

Adam's questions prompted me to look up these old pictures and post about this old hybrid.
Adam asked "Could you tell me more about this cross. Did you get a lot of seedlings out of this cross or just a few? What rugosa did you use? Have you breed anything out of it or did it turn out to be sterile?"
The rugosa I used was just an unnamed typical single-flowered, magenta/fuschia colored type. I always thought of it as "generic" rugosa. It's the same rugosa I've used as parent of pretty much all of my rugosa species crosses. Rosa xanthina pollen gave me big hips with lots of seeds and good germination. [A few years later I tried using the similar Rosa primula on the same rugosa and got no hips set at all.] All of the seedlings I raised to maturity were so similar that I couldn't tell them apart. They often  have a faint brushing of pink on the edges of the petals while still in bud, but you can't see any of this in the open flowers. The old [2004] photos below are kind of washed out by the bright sunlight but almost give you an idea of the color - a pale butter yellow. The scent is moderately strong and reminds me of Scotch rose scent. Actually I've always thought that this hybrid seems to want to follow Hurst septet theories - it has a lot of the characteristics of Rosa piminellifolia.
As for prickliness, the bottoms of the plant are fairly well armed but the prickles nearly disappear on the upper parts of the plant. Some of the tip top growth is nearly thornless.
As you might expect, this hybrid has never set even a single hip. It does make a little pollen and years ago I collected a bunch and used it for backcrossing onto the rugosa parent. I got hips and seeds but never germinated them (my fault, not the seeds). So as infertile as it seems, there is hope that it isn't a complete dead end. Once upon a time I also had what I believe was a partially converted branch (using trifluralin to induce polyploidy). The leaflet shape and substance had changed (rounder, thicker and crinkled) and the three flower buds I got to see were chunkier also. Sadly, that branch died back from some kind of canker shortly after flowering.
I dug a couple suckers from the original plant, still growing at my parents' house and planted them here last year. They're settling in nicely but haven't built up very much yet. I'll try to get accurate color pictures whenever it blooms.

1 comment:

  1. I forgot to mention, but it's probably obvious... the last two pictures are of a potted sucker showing the typical Fall color.