Saturday, February 5, 2011

Making Cold Stratification Easier

Over the last 2 years, I have been experimenting with the stratification process for rose seeds (this is where you give the seeds special treatment so that they have more uniform germination).  Some people do warm followed by cold stratification, but I have only used cold stratification, and it seems to work well for me.  The Rose Hybridizers’ Association (RHA) has more detailed information about rose seed stratification in their booklets on rose hybridizing, Rose Hybridizing for Beginners, and Rose Hybridizing - The Next Step (just google it).

During harvest time, hips are all collected into zip-lock bags together with other hips from the same cross.  The bag is then labeled with the cross.  What I always did in the past after the seeds were removed from the hips was to wrap them up in a paper towel (burrito style), then dip them in a large bowel of water *, carefully holding the wrapped paper towel in my hand.  Then I would squeeze out the excess water.  The damp paper towel containing the seeds would then be returned to the zip-lock bag that was labeled with the cross, and put into the refrigerator for 2 months.  This was done to simulate winter.  Note that rose seeds germinate much better after a cold period has been satisfied.  As you can imagine, if you have lots of seeds, coming from many crosses, the process of placing the seeds into paper towels, folding them, then moistening them and then placing them back into their zip-lock bags took a very long time to accomplish.  Also, since the paper towels tend to decompose while in the refrigerator, it was always quite an ordeal removing the seeds from the fragmented decomposing paper towels when it was time to plant the seeds.

Well last year, I decided to leave the seeds in the refrigerator after extraction from the hips, without putting them into the paper towels until the last 2 weeks of the cold stratification period.  I was very pleased to learn that germinations though delayed by 1-2 weeks, were just as good as the former method.  The advantage was that the paper towels did not have time to decompose, so that it was much easier getting the seeds out of the paper towels for planting.

This year I decided to try to make it even easier.  Instead of wrapping each group of seeds in a paper towel, I simply moistened a half sheet of paper towel, squeezed out the excess water and put the blob of moistened paper towel into the zip-lock bags making sure that it was in contact with the seeds.  This took half the time, and I used half the amount of paper towels.  Since I decided to do this with all of my seeds, I was a bit worried that it might affect germination.  Well, it is only 13 days since all of the seeds were planted and it appears that germination is beginning right on schedule.  I will be more certain in about 2 months whether or not germinations were adversely affected, but it looks like that will not be the case.  Stay tuned…..

* In case anyone has read my articles on my website about stratification, I have not been using Captan for the last several years.  Now, I just use plain water.