Siberian Pines - Part 2: Seed Stratification

Siberian Pines - Part 2: Seed Stratification

In Part 1 of the Siberian Pine series, I wrote about Pinus Sibirica and its value within the Northern permaculture ecosystem.

In this installment I will be writing about how I prepared the seeds for germination.

If you spend any time on the internet looking for information about growing pine nut trees, you will quickly discover that many of these species require some form of cold stratification to mature the seed kernels and trigger germination.

If you research stratification for Pinus Sibirica in particular, you are likely to find all sorts of weird, wonderful, and often conflicting information about how to do this.

So I decided to document the process I followed, in the hope that others may benefit from my success or failure.

I received 200 seeds in the middle of March.

I had contacted the supplier with some concerns that there would not be enough cold stratification time to be able to plant the seedlings in June. They informed me that from their experience only 1 month of cold stratification is needed, and they usually don't even bother with that. Without any seed treatment the supplier reported they get roughly a 50% germination rate.

The seeds came with instructions about how to cold stratify them, but they were a little vague, and of course conflicted with the other online info.

My conclusion from this research is that the cold stratification protocol is a reasonably flexible one, and it usually starts with soaking the seeds, which I did using filtered water. I also decided to ignore the warm stratification advocated by the likes of Rhora's because the majority of stratification protocols I found for Pinus Sibirica did not mention it.

During my research I read something about the seeds that sink during the soaking process being more viable than the seeds that float. I also immediately noticed that when I poured the seeds into the water, they all floated. Not a great start...

My research also suggested soaking times ranging from hours to days. I decided to soak them for 8 hours and see how things progressed.

8 hours later maybe 5 seeds had sunk to the bottom of the container, and the water was stained brown from the pine residue / resin. So I drained the water off, let the seeds sit for half an hour or so, and then put them back on to soak overnight in fresh water.

The next morning a few more had sunk, and so I repeated the process from the day before - letting them sit for half an hour, and then soaking them in fresh clean water for another 8 to 12 hours. 

My thinking around the seeds sinking is that as the seed coating absorbs water and it infiltrates the seed, the seed becomes heavier, and therefore sinks. Seeds that don't absorb water probably stay dormant which is why there is a lower germination rate. Anyway, time will tell and we shall see...

36 hours after putting the seeds into soak and roughly half of my seeds have sunk to the bottom of the container. It's beginning to appear that all the floating seeds at the beginning was a false alarm.

3 days soaking in water, and changing it every 8-12 hours and my seeds are ready for cold stratification. 156 seeds had sunk to the bottom, leaving 44 floaters which is roughly 25%.

I chose perlite to stratify the seeds in simply because I happen to have some handy.

I decided to perform two different cold stratification protocols to see which one is better. And I kept the floating seeds separate from the sunken seeds to see if they responded differently.

The first one will be my control, where half the seeds are placed in a plastic bag with vermiculite and simply placed in the refrigerator for 10 weeks.

The remaining seeds were placed in a different bag containing vermiculite, and will be subjected to the following:

• 2 weeks in the refrigerator 
• 2 weeks in the freezer
• 4 weeks alternating between the refrigerator and freezer every other day
• 2 weeks in the refrigerator 

What I am attempting to do is replicate the freeze / thaw cycle that these seeds would naturally experience as spring arrives. Anyone who has made maple syrup knows that this time of the year is when the first signs of life get kicked into gear as the phase transition cycle drives the sap out of the roots and into the upper branches of the trees.

This phase transition cycle of water inside the seed will also create a slow pulsing pressure upon the outer shell from the inside. As the moisture inside the seed freezes, it expands pushing out upon the seed casing. Then as it thaws it contracts, releasing the pressure, and drawing a little more moisture into the seed via capillary action. As this cycle repeats, I think that it will weaken the tough outer casing so that the seedling may successfully emerge.

This research study from 1925 on white pine seeds indicates that this protocol might indeed prove effective at increasing germination rates.

Siberian Pines

Siberian Pines

This year I decided it was time to grow some pine nut trees. But there is a challenge involved in growing these delicious nuts in the North. The pine nuts we know that are used in things like pesto, do not grow in our climate and is more suited to the Mediterranean and North Africa.

But there are alternatives, and they all happen to be very close relatives of White Pine. For example the Swiss Stone Pine, the Korean Pine, and the Siberian Pine.

I decided on the Siberian pine (Pinus Sibirica) or Russian Cedar for a number of reasons.

Firstly, their native habitat is the boreal forest (called the taiga) and so both the climate, soil, and ecosystem is very close to Northern Ontario.


Secondly, these trees produce thin shelled pine nuts which makes them easier to process.

And finally, Pinus Sibirica seeds are easier to germinate than the notoriously difficult Korean Pine.

But before I get into my experience raising these trees, let me explain why I think they are a great addition to a Northern permaculture landscape.

These trees are big. Like 100 ft tall at maturity big. Not a lot of trees around here do that, and so they will likely make great shelter barriers from the cold winter winds; creating small warm micro-climates in the landscape.

The Economics

These trees live for about 800 years although the typical forest age currently is around 400 years. 

Each tree produces on average 5 Kg of pine nuts every year (up to 10 Kg in a mast year). 
At the current price of $75 per Kg, a tree can produce an annual income of $350 per tree once you factor in squirrels, "processing slippage", and the odd bad year.

Now consider a shelter belt of 100 trees and let the math sink in. That is a $35,000 per year income for maybe 1 month worth of work harvesting and processing. Every year for 500 years (Allowing for old age retirement, tree losses due to disease, fire and natural attrition).

That is an income lasting half a dozen lifetimes, or a dozen generations. Such a shelter belt would have the potential to generate $17.5 million in pine nuts alone. Not to mention the other benefits these trees have in the ecosystem.

OK enough of the boring numbers. Needless to say, these trees pay the bills.

The tree is seriously hardy. It even grows in permafrost. And its resin doesn't crystallize quickly as common pines do. In its native land, this resin is a natural resource useful for many different applications that I won't go into here.

The Nuts n' Bolts

Pine nuts are generally ready for harvest about 10 days before the green cones begin to open. And in the case of Pinus Sibirica, the cones never actually open which makes determining ripeness difficult. 

In its native habitat there is a bird called a spotted nutcracker is responsible for extracting the nuts from the cone and dispersing them. The spotted nutcracker doesn't live in North America, but the Clarke's nutcracker does. It may be a good indicator species for nut ripeness but alas, they don't range into Northern Ontario.

This little guy is a Red Breasted Nuthatch, and they do migrate into Northern Ontario. They also happen to be great eaters of conifer seeds. Maybe, just maybe a flock of these descending upon your pine nut trees to feast could be subtle sign that it's time to harvest.




Another possible indicator bird is the Pine Grosbeak.

The cones are harvested with either long poles (often bamboo), long-handled pruners, or long-handled saws which knock the cones down.

The harvested cones are placed in a breathable bag and then exposed to heat / left in a sunny, sheltered position for 3 weeks. The drying process causes the cone to fully ripen, and at this point they can be broken apart to extract the seeds. This is generally done with a mechanical threshing machine to save time and labor.

Now I'm wondering if these little guys might be eager workers we can recruit to harvest the pine cones. They naturally chew through pine cone stems to detach them from the tree. They then collect the fallen pine cones and stash them away in a safe spot for future use.

It will be an interesting experiment to see if they will harvest and store pine cones if they are provided with a convenient storage space, and the cones they collect are replaced with another food source, like peanuts in the shell.