January thaw
This year we are experiencing a classic January thaw in Ontario. Not only we have above 0°C temperatures, it is also raining. It is a welcome respite from frigid temperatures for both people and plants, and also on this occasion the snow cover gets diminished (where applicable), with nice surprises showing up!
The jump to an unseasonable warm weather in mid to late January, is a weather phenomenon most usual observed in specific Northern Hemisphere regions called January thaw; also called ‘bonspiel thaw’ on the Prairies provinces. Actually it lacks a formal recognition as being a meteorological event and it is not even happening every year (or it can be a February thaw).
Seeds-wise, at the end of January we are at a crossroad. We can still sow species that require cold/moist stratification (fingers crossed it remains cold enough until March) and also start sowing species that require only a short cold/moist stratification or even warm germinating species (with good indoor lighting systems).
Sowings of Gaultheria humifusa and Oenothera macrocarpa: the bundled up pots are in the fridge for about 1 month of cold/moist stratification; the front row pots are kept at room temperature (+/- 20C enclosed in a plastic bag).
I personally wait a bit more for sowing the straightforward warm germinators, but two recently packed species in a couple of orders caught my attention. Both Gaultheria humifusa and Oenothera macrocarpa, are considered warm germinators and allegedly may germinate better after a short cold/moist stratification period. I never had the occasion to sow them before and had to trust the germination advice from other sources.
It is a good occasion for a little experiment!
For comparison, I have to try them both ways: 1) direct germination at room temp., and 2) with 1 month of cold/moist stratification (in the fridge). We’ll see which ones germinate better and I’ll show the results later….
It is well known that various species that otherwise qualify as warm germinators (seeds only have physical dormancy) may benefit from a period of cold/moist stratification, which allows for a more rapid breakdown of the seedcoats and start of the biochemical processes involved in the germination initiation.
In some cases, instead of a slow germination of 1-3 months at room temperature, we may obtain a more rapid and uniform germination after a short cold/moist stratification; so it is worth trying it.
For the same reason, if you like to do just one sowing for all your seeds in late fall/winter, it is OK. The warm germinators will germinate in the spring with the raise of temperature, usually with a greater uniformity.
Let’s keep in mind that germination patterns for any given species can vary depending on the collection locality and mother-plant characteristics (epigenetic factors), so do not be surprised if your results don’t match sometimes the generally claimed germination requirements.
Winter time is best for learning more about propagating various species from seeds and about germination in general. Not to mention that we also end up with nice plants for our gardens!
