Normally after the winter indoor germination period comes to an end I let the seed trays dry out and eventually dump them in the compost bin. This year I moved them outside and kept watering them. We have had some extraordinarily hot weather for Guelph already this year (high 20s to low 30s, Celsius). And all of the sudden I have seed lots that are germinating like crazy in these high temps. Several seed lots had not germinated until they were outdoors and in these temps. Has anyone else experienced good germination at higher temperatures?
Hi Elizabeth,
I was able to germinate and grow some seedlings out of polyantha seed in the middle of our summer which just passed us (Dec 2011-Feb 2012). It was a cool summer, the temperatures were similar to those you are noting in your message, mostly under 30 celsius if I recall correctly. Those seedlings performed very well throughout the summer and beyond. We did not have furnace-type conditions.
I also tried to germinate some various other types of rose seed (non-polyantha) in those conditions, but had to put it back in the fridge as it refused to sprout. Some of it did however germinate when temperatures dropped by the time fall set in well and truly.
Oh yes, I forgot to mention I also germinated a TON of Grouse Immensee X OP seed in that summer, supplied by David Z (thank you, sir). I only kept the nicest one of them, all grew like weeds, I had no space for the lot!
I leave the trays under domes till the third year and will have germinations at the higher temps, also there are those that do not germinate till the second year, plants I just let OP with an occasional dusting of pollen. Neil
Liz, the change of temperature has made the seeds think spring has come.
Peter
Some plants, including some roses, grow faster at higher temperatures. After the chilling requirement has been satisfied, they may not grow much if the temperature remains low. But as soon as they feel the heat, they take off.
In other cases, there seems to be a “heat dormancy”. That is, a dormancy that is broken by heat. This is in addition to “cold dormancy” that is broken by chilling.
Rowley (1956) recommended keeping seeds warm for two months of “after ripening”, then cold for an additional two months. This method worked so well for Rosa canina seeds, that he adopted it as a standard method for all rose seeds.
Risley (1958) tested seeds from ‘Skinner’s Rambler’ pollinated by various other varieties and species. Seeds from ‘Max Graf’ as pollen parent sprouted in 83 days, while those from ‘Queen of the Lakes’ took 173 days. The difference is probably an indication of the preferred growing temperature of the seedlings - those from ‘Max Graf’ growing better at lower temps., and those from ‘Queen of the Lakes’ preferring heat.
Karl
Some random seeds germinated this week – now that it is warm out: Bride’s Dream and Toprose. Theyre also among the largest seeds of the group.
Whcih reminds me that each rose group seems to have some prerequisites, and that finiding a unified pattern for all seeds isnt always really helpful.
Um George, ‘cool’ temps under 30? If you ever visit Canada be sure that it is in summer and bring long underwear. Locals are wearing shorts when it gets above 10 celsius… It is 36 in the shade today and it is not a ‘dry’ heat. The locals are hibernating today.
‘heat dormancy’, eh? Good to know. I am definitely going to make a habit of doing this in the future. I’m begining to wonder if I have dismissed some potential seed parents as being poor germinators…
Hi Liz,
I wonder what your nighttime temperatures have been? With cooler nighttime temps, even if the days are warmer, I get fair germination. It is when both day and nighttime temperatures heat up that germination stops for me.
Jim, good question. Most nighttime temps in the past few weeks have been in the low 20s or high teens. There was a week about a month ago where monday was in the low 30s, but by friday we had a high of about 10. Perhaps it is a combination of factors going on here that is causing this: cycling of temps, a heat treatment, and just additional time. Looking at the pedigrees there are 3 parentages that kind of stick out. A fair number of these have Baby Love or Prairie Celebration in them on a mixture of seed parents. The other one is a particular cross, Alberta x Karma.
Um George, ‘cool’ temps under 30? If you ever visit Canada be sure that it is in summer and bring long underwear. Locals are wearing shorts when it gets above 10 celsius… It is 36 in the shade today and it is not a ‘dry’ heat. The locals are hibernating today.
Well… I am downunder ya know !! LOL
Actually Canada has always interested me as a cool destination (pun intended).
I actually prefer weather like we are getting here now in winter (temps 8 celsius - 15 celsius).
Whcih reminds me that each rose group seems to have some prerequisites, and that finiding a unified pattern for all seeds isnt always really helpful.
… after being on this forum for several years now, and hearing all the different experiences y’all have had with stratification techniques / temperatures / to warm stratify / to not warm stratify/ optimizing germinations of particular types of seed by adjusting stratification temperatures etc etc… I would really have to agree 100% with that statement Michael made, which I have quoted.