ProfessorRoush has spent the last 3 years puzzling over the provenance of a perfect little rose seedling that I found in the shade of 'Hope for Humanity' late one summer. Praying that I had a new little self-seeded hybrid of my very own, I transplanted it to a new bed where it would get plenty of sun and I waited for it to bloom.
At the end of a full growing season, in 2012, the rose was about 12 inches tall, and still perfectly healthy, but it did not bloom. It was obviously winter-hardy and had no blackspot. It had small foliage of 7 leaflets that roughly resembled a R. spinosissima, but the only two R. spinosissima hybrids I've ever grown were 'Harison's Yellow' and 'Stanwell Perpetual'. 'Stanwell Perpetual' had been grown near the birthing site about 6 years ago, but was long dead. Could this rose be from a surviving root of that rose? If it was, then why wasn't it blooming?
I waited another year, believing that even a non-remonant rose would bloom at the start of the 2013 season, but the plant still didn't bloom. By that time, my theory was that I had a seedling of R. arkansana, the wild rose of the local prairies, and I was kicking myself for thinking it could be anything else. But R. arkansana's foliage in the nearby prairie looked bigger than my rose, and by the end of last season, the rose was 3 feet tall, with long canes and small short prickles everywhere. Thankfully, it was still completely free of blackspot. But what was it?
This week, the mystery was solved for me. The rose has been blooming with these little pink single-flowered blossoms. I looked at them, looked over my shoulder at the R. eglanteria (R. rubiginosa) growing in another bed, and I confirmed the identity of my seedling as R. rubiginosa by rubbing a few leaves and releasing that nice green apple scent. Somehow, (a bird?) Shakespeare's Sweetbriar rose had seeded itself 200 feet away from the bed in which it grew.
I suppose it could still be a hybrid, but I can't tell my rose from the species at present. We'll confirm it again when hips form. Mystery solved, but do I really want another monstrous R. eglanteria near a pathway and short of room? I think not. It'll have to be moved.