Wondering if anyone can help me figure out how to cold stratify my rose seeds, Rosa Rugosa. I’ve been all over the internet and all the information seems to contradict itself. I want to use my fridge since it’s the most temp. controlled, I’m in zone 5? near Boston.
So can I use those jiffy pellets or should I just use the paper towel with water in a plastic bag?
Does there need to be a peroxide mixture to the water?
Should I block light from getting through the platic bag or greenhouse?
Do I need to open the bag every day? For how long?
Can I start stratification now if I plan to grow them indoors for a while or should I start in fall? What month?
Biggest question: how long should I cold stratify my seeds? Some people say 6-8 weeks others 3-4 months.
I really want to get this right. The plants are going to a women’s center for their yard/garden. They are both for beauty and to help support the local American honey Bee population which is endangered. Thanks for taking the time to read and respond. There’s no rose growers association in my area that I can get to.
Happy blooming
Francesca
With R rugosa there’s no right to get. They are a bit temperamental. For instance, I collected old hips that had been outside all winter. I started stratifying them in May, with moist peat in a thin plastic bag. No peroxide needed. Over many months they germinated a few at a time. That was a couple years ago and I am about to get the first bloom from one of the seedlings.
In fall of the same year I collected a lot of newly ripe hips and stratified them. Over many months, roughly from New Year on, there were sporadic sproutings. I had so many seeds I lost count after a while of the germination rate. The seeds (achenes) are very small so you may get 50- 100 per hip. Even 10 % germination gives a lot of seedlings to deal with.
On the main page of the RHA site there is a long review article that I wrote on germination. It tells about all the ways people have tried with rugosa, and other species. SO if you want more details you can read there.
Hi Francesca,
Larry sure put together a great resource on germination.
In a germination experiment I did a few years ago looking at the effect of putting seeds directly into cold stratification without drying and short term drying of seeds before stratification, short term drying reduced germination with the open pollinated Rosa rugosa alba seeds I used. I had multiple replications of 100 seeds in each treatment and ran stats on it and the t test picked up a significant difference. Germination was 61.8% for straight to stratification without drying and 48.6% for short term drying (4 days). Close to 50% of course is still great with all the seeds they produce. Some roses it didn’t matter, but for Rosa rugosa drying seems to matter. Across the species and cultivars I looked at drying never helped germination. My suspicion was that maybe it could because supposedly the germination inhibitor ABA may be more soluble (leach out better) because of changing a bit upon the seed drying. The same detrimental effect of drying of R. rugosa seeds is reported in an article looking at R. rugosa on the British Isles, so I am not along in experiencing this.
So, after you harvest the hips you may want to not let the seeds dry out. I have some data from a couple years ago I need to finish analyzing looking at different stratification durations on germination with Rosa rugosa and other species and write up. One trend that generally seems true across roses is that the longer the stratification duration (within reason and the optimum differs across roses), the more uniform the germination is after the seeds come out. With difficult to germinate species or cultivars some people have been very successful keeping them in the fridge indefinately and eventually weekly taking them out to see what germinated and then pot those up. The container then goes back in the fridge for another week or two and then is checked again.
It sounds like a wonderful project and service you are doing with pursuing this project!!! I have high pH water (the city puts in sodium hydroxide to elevate the pH to protect corrosion of metal pipes) and it is important for me to acidify my water before I water my rugosa seedlings inside or they become very chlorotic because of not being able to take in enough iron. I also add a little powdered elemental sulfur into the potting mix before potting them and it sure seems to help a lot.
Sincerely,
David