Picked up a few dropped climber OP hips from the ground this weekend (I dont know all the climbers - compassion is among them).
We have had temperatures in the 20s and below. Are these still usuable? Do they still need a stratification period?
I think you could sow them straight away.
It is sure worth a try. I remember years ago Dr. Leo Dionne (has anyone heard from him in recent years?) shared a good rule of thumb. It was that if the canes of a rose are killed by cold it is likely that the seeds in the hips on it likely are damaged as well. There are exceptions of course and it is still fun to try and give them a chance.
If they don’t start to germinate in a few weeks or so, I would give them some cold. Stratification needs moisture for the biochemical changes to occur efficiently and maybe on the plants they aren’t effectively being stratified if they dried out too much. Over time “after ripening” can occur in species where when dry dormancy dissipates (many of our typical garden species where we buy seeds dry in packets), but I’m not sure to what extent that happens in roses. My suspicion is not to a great extent. Maybe it would be a great opportunity to practice Don Holeman’s embryo rescue technique and you can at least see if the seeds are viable and enjoy some seedlings soon if they still have some dormancy.
I second David’s remarks. I believe it very much depends on the variety you are collecting from. Years ago I once collected seed from an unidentified Centifolia type shrub and sowed them in a pot in the Fall. The pot remained outdoors all Winter, sitting out in the garden, unprotected. It was exposed to cold well below zero F many times, and yet those seeds germinated in the Spring. Modern Hybrid Tea seeds would not remain viable after such extreme cold exposure.