Are there any observations about which of the two processes - flower formation or rosehip formation - is more strenuous and stressful for the rose? So far, with busy reapeat - flowering roses, I’ve always tried not to use the entire flowers for fertilization, so as not to weaken the plant and its resources too much. Finally, there are other stress factors that come into play. In addition to protecting the mother rose, I also hoped for better crossing results. Of course, this carefulness only makes sense if the formation of rose hips is actually more stressful for the plant than the development of new flowers. Summer blooming roses are an exception, as they have more time for regeneration anyway. I would be grateful for any comments. Many thanks!
With absolutely no data to back this up…I’d say that supplying the necessary carbohydrates to bring embryos to maturity / creating a fruit is more stressful than flower development. But it may depend on whether we’re talking hips or watermelons.
There’s no benefit to leaving flowers unpollinated. The plant can handle every flower that gets fertilized. It’s not stressful for the plant to create mature fruit, even lots of mature fruit. The worst than can happen is that the photosynthate gets spread thin and the fruit (hips) have less flesh than they would otherwise.
The seeds themselves only require a fraction of the total photosynthate that gets pumped into the hips.
If you are lucky enough to generate so many seed that this happens your biggest problem will be seed and seedling management. Given the relative infertility of most crosses this is not a likely outcome anyway.
Another thought on this matter since you brought it up is that roses are unique among rosaceae in that the flowers are the part that have been selected for carbohydrate loading. In all other rosaceae that I can think of some other tissue of the fruiting body is where the photosynthate is loaded and the selection in all those cases is for food production. Rosa is the only rosaceae selected primarily for aesthetics.
Thank you so much for this valuable and clear statement!