I’m just a hobbyist-- I haven’t attempted making crosses of my own (although many fascinating possibilities have occured to me!). Instead, I just grow the OP seeds. I have two questions:
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In your experience, do you have any idea of roughly what percentage of OP seeds are self-pollinated? I guess I should mention that my roses are all modern (at this point) and are primarily HTs and floribundas. I realize some types of roses(rugosas?) shed their pollen quite early, which would increase the likelihood of self-pollination.
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Have you verified the sinking/floating seed germination idea which is commonly accepted? I can’t remember which, but I remember one rose hybridizer saying he ignored that as he had “floaters” germinate. I’m doing an experiment this year and on batches of seeds which are large, I’m dividing them up between “sinkers” and “floaters” pre-stratification. I’m waiting to see if I have a dramatic difference in germination between those sets. Just wondering if your experience validated this common belief.
Thanks in advance for your answers. Someone at the Rose Forum at Gardenweb gave me a heads-up about this forum and I’ve been reading with great fascination and enjoyment since then.
Alicia
I’d guess that most OP seeds from modern roses are from self-pollination, although I couldn’t give you a percentage.
Some floaters do germinate. It may depend partly on the seed parent. Some varieties of rugosas only produce floaters, but the seeds germinate very well.
I agree with Jim. It seems that many diploid roses are self-incompatible and many modern tetraploid or even some triploids can readily set seed from self-fertilization.
I haven’t come across specific percentages of germination between floaters and sinkers. For myself I typically save all seeds from crosses and bulk them without a float test. However, when I am doing germination experiments with roses looking specifically at the effect of temperature or some other factor I use the float test. For the germination experiments I’ve done/am doing I want to minimize the variability due to other factors besides what I am testing and I am typically using open pollinated seed to get high enough numbers. Throwing away the floaters isn’t a problem in this situation. Like Jim said, rugosas typically float.
Rugosas are typically self-incopatible although they release their pollen before the flowers open. Therefore, op rugosa seedlings are typically hybrids with another rugosa genotype or some other rose nearby. If you look closely at a rugosa cultivar planted in isolation you will typically not see many or any hips on it, but if around other roses (especially another rugosa) you typically do (that is if it is fertile). A few years ago some people were suggesting on the web that ‘Hansa’ is not a straight rugosa hybrid because op seedlings of it showed very non-rugose characteristics. They have not considered the strong self-incompatibility mechanism in most rugosas and the fact that most of their roses near Hansa were modern roses and not rugosas. We can use trends for incompatibility within roses to have an idea which roses op seeds are more or less likely to be due to self-fertilization and make decisions from that knowledge based upon our objectives.
Sincerely,
David
Welcome to the forum if this is your first post. Good luck with your germination test, be sure to keep us posted of the results. If possible, it would be interesting if you recorded the seed parents to see how much variance there is between cultivars.
Good Luck
Robert
Thank you, all, for taking the time to respond. I’m overwhelmed, really, since I know my questions are so basic and I know that what I’m doing isn’t as exacting as selecting cultivars to breed and then carrying out the process. I enjoy reading the posts here and I appreciate your willingness to share your knowledge.
Robert, I will do my best to keep track of my sink/float varieties. They are packaged separately, but what I’m afraid of is that I’ll forget to keep track of how many germinate in each set!
Alicia
I can offer a little different perspective on the whole sinking vs. floating subject.
I have no idea weather floaters are any less viable and sinkers. I keep all of the seeds and dont bother separating them. There is something that the floating seed test has given me. Fun.
What I do is cut the hips up and take the seeds out. I then give them to my 4 year old daughter to put in a cup of water. Then I make a big deal out of floaters and sinkers. Believe it or not, its makes the whole thing fun. We cheer for sinkers and say bummer for floaters. What make me laugh(and very happy) is how long my daughter will actually sit there with me doing the float test. In the end, I put them all into the petri dish which she has carefully filled with my sand peat moss combo regardless of floating or sinking. Its a way to make a sometimes tedious process a little more fun.
So far thats the only real use I have had from the float test.
Glad I have not tried any Ragosa seeds. I would have a bummed out little girl.
Steve J.
You are my type of hybridizer - have fun with what you are doing. As an amateur, I have always said - when it isn’t fun anymore, then it’s time to quit! Keep on having fun - hopefully your daughter will give it a try one day with her own seeds.
BTW - I do the float test, but the main purpose to soak in a clorox solution before statifying them all.
I plant them ALL every time and keep the floaters separate, but put them into one corner of the seed tray very close together. I may get a single seedling from 15 to 20 floaters at times. Some times none.
George, is it possible that you are not observing something due to most floating seeds not being viable seeds but instead you are seeing the effect of planting the seeds “very close together”? One “theory” is that the germination inhibitors have to leach away from the seed before germination can take place.
Over the past couple of years I have been running somewhat of a casual test on “floaters”. During this time I have separated out the floaters and split them transversely and observed the seed within the achene. I have probably split several thousand seeds and I cannot think of an instance where the seed appeared viable. Either the achene was hollow or the seed was shriveled.
As a validation, from each batch of seeds I also split several of the “sinkers” and the majority of the seeds were white and filled the achene.
I have also observed that after stirring the seeds in water a certain percentage may also sink slowly. I found these to have similar characteristics to the floaters when cut.
Based on my limited observation and testing I have convinced myself that the floaters as a rule are not viable. I now discard all floaters. But this is only an opinion based on the roses I work with.
I know this does not necessarily apply to rugosas or some other species but for the tetraploids that I use I feel confident.
John F, the vast majority of floaters that I have opened are as you say - empty or with shriveled seeds. I have opened some however, that appeared viable - probably at about the level that George Mander indicated in his seedlings. I just plant them all, just in case!
Jim Sproul
Jim, I am glad that somebody agrees and does the same as I do. It does not take much space in your seedtray as I put ALL the floaters into one corner with no space in between the seeds. I separate them from the sinkers with a piece of thin aluminum strip stuck down across the corner.
It’s not all the time that the odd one will germinate.
George Mander
Last weeks 60 open polinated seeds of roses I collect germinated. I separated the floating from the sinked and looked what happened.
35 OP seeds from a yesterday looking bush -/+ 30% of the floating seeds germinated. +/- 70% from the sinked germinated.
From a Rosa Canina hybride:
From all the germination 50% are from floating seeds and 50% from sinked seeds.
From other seeds some floating and sinked seeds germinated.
Desperate thing…I don’t know the name of the roses. This year I hope to ID them.
So my opinion: Never discart any floatings!
I plant everything I get. Too much work separating out the floaters. What germinates, germinates. 
Paul
Me too Paul. I’ve never understood why people got so wrapped up in whether seed floats. I’m more interested in knowing whether seed germinates.
I agree, Robert. I think it is just time wasted. It is easier to cull if I have too many, anyways.
I think the only point in a float test is for scientific usage, or if youre working with one rose specifically, and want to predict generalized numeric outcomes. For instance, Im sure Zary used Gemini quite a lot, so I am sure it is a worthwhile test! But that is quite the exception.
I did this because I read a lot about this. I wanted to see it with my own eyes.
I occasionally have crosses that produce many seeds but few germinations. If the float test was reliable, it would save me considerable time and space when planting those seeds. Unfortunately, I don’t know of a cross where the float test is 100% reliable. I did try it on a few crosses this year. We’ll see…
The problem is, the float test might be reliable with some crosses and unreliable with others. Even pollen parent could theoretically affect outcome.