Results on Rubus chamaemorus germination – update 2 and 3

For those who didn’t follow the story from the beginning, please see these links:
Homework for today: Rubus chamaemorus germination – December, 2019
Preliminary results on Rubus chamaemorus germination – update 1 (Jan. 10, 2020)

Lot#2 has been eliminated (the seeds were damaged during the endocarp removal).

Lot#1 – the first signs of germination appeared pretty fast, with the radicle emerging first, in most cases.
A few seeds were also discarded, but almost all the remaining ones showed signs of germination (radicle growth and greening of cotyledons).
The container/and the pot with transplanted germinated seeds have been kept under light at +/- 20C.

The main aim of the experiment was to see if the seeds indeed germinate at warm/room temperature, and they do.
But excising the seeds from the pyrenes is not an easy job and many will get damaged during the process. Especially for large lots of fruits, it is a completely unpractical method.

Another attempt is being made by using a hot water treatment (hwt) on the pyrenes. The hot water treatment gave excellent results last year for replacing the mechanical scarification usually employed for Fabaceae seeds.

Lot#3 was treated with boiling water 3 times, one day after another starting on Jan. 16, and then placed in the same conditions like lot#2. We’ll see if the treatment was enough to produce fissures in the endocarps and allow germination without extracting the seeds.
Update will follow.

 

Recap:
If Rubus chamaemorus fruits are sowed, they require 270 days of cold/moist stratification in order for the endocarp to broke down and allow the seeds to germinate. Translation: for fruits sowing in late fall, expect some germination in the third spring after sowing.

If you manage to remove the endocarps without damaging the seeds, they will germinate quite fast at warm (room temp.)/light.

 

Update 3 – regarding germination trials out (2021):

First, because I had a question about it: what went wrong with excising the seeds from within the pyrenes?
The problem was that using a very sharp scalpel, the seeds were damaged while cutting through the pericarp. Microscopic cuts or punctures led to the damage of the seeds and embryos.

Unless one is a surgeon, I don’t see it as a feasible method, even if the few unharmed seeds did try to germinate.

So, in early spring of 2021 I went back to a classical method of scarification used by plant nurseries for this type of ‘seeds’ by using  sulphuric acid. This is not something that can be applied at home and I don’t know if it is much in use in the nurseries nowadays; out of curiosity I had to give it a try.

One lot of seeds was treated with sulphuric acid for 45 min and another one for 1 h.

Afterwards, the ‘seeds’ were kept under lights at room temperature, and… nothing happened. Some seeds seem a bit enlarged but obviously the time wasn’t enough for the endocarp to be eroded enough in order to allow water imbibition.
Later on I found one study suggesting a 3h treatment with sulphuric acid; maybe I will try it this coming winter.

 

Also, another more friendly method, like nicking, was also tried with no success.
Then I left a sample of pyrenes sitting in water since March! I thought that some may give in and imbibe but it didn’t happen.

 

Conclusion: for home gardeners sowing as usual and patience may provide the best outcome in regards to germination of this species. Repeated cycles of warm/cold/warm/cold are necessary for the endocarp to broke down and allow water imbibition of the seeds and start the germination process.