Knowing that they won’t bloom for a while, but having entirely too many…
Do folks have any rules of thumb for culling species seedlings? I read of (I think it was a double “azalea” flowered snapdragon) some seed for which growers were advised to discard first germinations as they would not be of the desired form, and I wondered if there is a temporal guideline as to which seed might be more interesting, or any other thoughts… (My gut says earlier germinations are just better for the most part…)
My inclination is to keep the earliest, the latest, the most vigorous, one of the more compact, and if any other phylogenetic distinction is noticeable (e.g. apparent levels of anthocyanins in stems), try to save each (healthy) extreme, but that’s already too many…
How do others evaluate species seedlings for culling?
I don’t think you should make any sort of determination based on germination sequence. I like your ideas about vigor and anthocyanins better because you are observing them directly rather than discarding arbitrarily based on someone else’s supposed experience. I advocate for allowing emotion to be a part of the selection process.
Our mission as breeders is to shape the flow of the rose as it mingles everchanging with humanity. By concentrating your attention on the selection process, you are trusting yourself to shape a portion of this flow. Who knows which seedling will make its way out into the world and like a butterfly flap its wings to cause thunderstorms across the world. Maybe it will have your style.
Therefore allow yourself to be a part of the selection process, making every effort to find observable phenotypic variations that cause even a subtle emotional response. If the differences are too subtle and numbers require immediate culling, handle each rose one by one and make intuitive choices hoping your subconscious knows what it’s doing.
Unfortunately species seedlings can be quite uniform in vigor, which is the earliest culling criteria to maifest. Always discard non-vigorous seedlings. (This priority is shaped by my climate, where strong vigor is necessary for a rose to thrive.)
Any early non-uniform leaf health problems are of course a top criteria. Mildew can strike early in the greenhouse and makes for an easy cull. In once case I had a flat of seedlings that mildewed uniformly but for two seedlings. That was an easy selection but most others were not. Many species seedlings are uniformly healthy in the seedling tray.
When a batch of species seedlings is largely uniform in vigor and health, thorniness may be the first discernibly variable characteristic. Normally I select the least thorny, as I would like to direct my portion of the flow towards thornlessness. However, when I attempted R. carolina x Prairie Peace I selected the thorniest plants in hopes of finding a successful cross.
BTW, David’s warning on this forum about using R. carolina and R. virginiana as females is valid. He and others warned that R. virginiana seems to vastly prefer its own pollen and even successful crosses might look like all the other seedlings. That is pretty much true. I devoted one R. carolina/virginiana bloom flush to attempting to prove him wrong by pollinating R. carolina and virginiana like mad. I pollinated blossoms after they opened and left the blossoms intact, hoping for some selfs to make the hip setf. I ended up with tons of seed from labeled crosses and it germinated like grass. It would have taken acres (figuratively) to plant out all of those seedlings. They all looked nearly the same in most cases. All I could do is look at each seedling as I was planting and toss it or plant it, so I went by the thorns as I mentioned or just intuitive selection. All in all I planted out 100 or so (maybe less as my mind exaggerates the scope of anything that involves me actually working) and a handful ended up showing signs of hybridity when they bloomed two years later. (I am super lucky to be able to plant them out.)
I’d imagine it’d depend on what species and what you were intending from the cross, I feel like usually there’s an aim when using a species, I mean some species are obvious like R. glauca (thornless and foliage colour are likely the main superficial traits people are after from it). It’d also depend on what is the seed parent as you’d be looking for signs of the pollen parent to determine successful hybridization. There isn’t a one size fits all answer…just got to trust your own instinct and judgement.
I was thinking recently that some of the early growers who raised seedlings from ‘Parson’s Pink’ rejected the weak seedlings, and thereby missed out on the minis.
Any early non-uniform leaf health problems are of course a top criteria. Mildew can strike early in the greenhouse and makes for an easy cull. In once case I had a flat of seedlings that mildewed uniformly but for two seedlings. That was an easy selection but most others were not. Many species seedlings are uniformly healthy in the seedling tray.
I recall one case of a woman who found that her flat of seedlings were all (or nearly all) mildewed. She kept them anyway, and was pleased to see that they outgrew their susceptibility. I wouldn’t bet on this happening very often, but it is worth mentioning.
I read a similar piece, many years ago, about seedling petunias. Those that grew vigorously were destined to bear single-blooms, whereas the runts would be double-flowered. I don’t know whether that rule still holds, or was limited to the early strains that segregated for single and double.
These cases presumably involved linked characters, which is an important subject.
And on the subject of seedlings, continuous lighting can induce seedlings of some genera to grow vigorously and mature much earlier than usual. E.g., Black currant seedlings 2-2.5 months old looked like 2 year-old plants. http://bulbnrose.x10.mx/KKing/ContinuousLighting.html
I have dozens of crosses onto virginiana that I have no intention of germinating on account of not being able to discriminate f1 hybrids. It is a lot easier to do so when the species is the male parent.
Wow, Joe. I like your artist’s/breeder’s mission statement. You should have saved that for the newsletter!
Vigor is one that everyone always touts, but like Karl, I’ve wondered if that doesn’t eliminate the selecting for compact plants. Clearly breeders like David Austin select for vigor, and I see lots of gripes about his plants putting too much into growth. I suppose vigor and size differ in some contexts, but for a species that won’t bloom for a couple years, I wonder… I think I will just look at foliar and stem color and apparent health and be done with it. Alas, I just pulled a second batch of seedlings from this lot after a second round in the cooler, and I have some serious culling to do.
Climate has a lot to do with the vigor of at least a few of Austin’s roses. For instance, Graham Thomas described ‘Graham Thomas’ as a four foot shrub, a little too upright. That’s just how I saw it growing in Eureka, CA. However, the specimen I had in Mission Viejo, CA was all long, thick canes and few bloom. Even in San Jose, CA ‘GT’ was too bushy and not as floriferous as it was further north.
I had ‘Swan’ growing in a large container (So Cal). Even there it was very vigorous, and probably bloomed more than it would have growing in the ground.
On the other hand, ‘Wife of Bath’, ‘Fair Bianca’ and ‘Bredon’ were strong but mannerly growers. ‘Windrush’ was strong but rather sinister looking with its ghostly flowers floating around the black canes. Just the thing to plant beside the bay windows of a haunted house.
David’s warning on this forum about using R. carolina and R. virginiana as females is valid. He and others warned that R. virginiana seems to vastly prefer its own pollen and even successful crosses might look like all the other seedlings. That is pretty much true.
You can mitigate this problem somewhat by flushing the anthers prior to making the cross pollination, a practice advocated by Paul Barden in an earlier post here.
On that basis I ran an experiment with virginiana in which I used a spray bottle of tap water to flush away pollen that had landed on the anthers then protected them with a polyethylene sandwich bag with no further pollination. The result was that most of the hips aborted and the ones that did develop only had one or two seeds containing embryos.
You have to catch the bloom as it opens especially in dry conditions, and be aggressive with the flushing.
In my first attempt I intentionally left the blossoms unwrapped with the idea that some self-pollination would help the hip not to abort. I guess it worked, but I basically had to grow the seedlings into three or four foot plants before I could detect signs of hybridity. Not practical for most of us.
A later attempt on R. carolina where I was a little more careful to discourage selfing resulted in very few hips from a lot of controlled crosses, just as you describe.
Warren, have you used R. davidii exclusively as a pollen parent as well?
