I wrote in May (2014), of the crazy amount of walnut seeds that I had collected the previous fall and, then, subsequently stratified them in the refrigerator.  In that post I wrote in May, I mentioned how nicely the seeds were progressing with their growth and development into seedlings, nice looking and appearing to be strong.

<figcaption class="wp-caption-text">Walnut Seedling (May 2014)</figcaption></figure>

Sadly, now, at the beginning of September (2014), all of the walnut seedlings that grew from seeds that we stratified, have died.

This is a frustrating; I invested time, effort and a bit of money with the purchase of some clever root-pruning pots, but I decided that I should try learn what went wrong.  I suspected the growing medium – a natural, coconut hair-based substance that we tried this season for many of our seeds.  We started tomatoes & other long-run vegetables, morning glories, and various oak acorns in addition to the walnuts in the coconut-hair stuff.  My unscientific verdict on the grow medium is a mixed bag.  Walnuts, oaks and morning glories started out very well.  Tomatoes took a very long time to grow – even with artificial light and heat.  The tomatoes did not take off until summer warmed up slight – this was a month after we had put them into the real soil of the garden.  The oak seedlings, however, did well.  Most are still alive.

I decided to Ask an Expert.  So, I emailed the University of Minnesota’s Extension Service.

Walnut question.

Last year, I was traveling the midwest (via roads), and when I would stop, and if there was a walnut tree, I would collect some nuts. I cleaned the nuts, did a float test, and then stratified the sinkers in the refrigerator until spring. I kept a log of where each nut from from, when it was collected, and how long it was in the refrigerator.

I should also mention that I picked up various oak acorns on my travels, too. (this bit of info is pertinent a bit later)

I planted the nuts in a coconut-hair-based grow medium (this was this spring), and put them in trays and set them on a grow-heat-mat. By late spring, I had a lot of nice looking walnut seedlings. I transplanted these seedlings into RootMaker brand, one gallon containers, and set them outside. I used a regular, unfertilized garden-type soil from Menards for filling the remainder of the pots. The coconut-hair-based grow medium came along into the new soil.

During this transplant period, I also found about a half-dozen squirrel-assisted walnut seedlings in our yard and woods. I transplanted these into RootMaker pots, as well.

Fast forward now to the end of August, all of the collected/stratified walnut seedlings have died. There is not a one that has survived. The oak seedlings that I started – using the same grow medium and processes as the walnuts — have more or less survived. Several did die, but not in the percentages that the walnuts did. The other thing to mention is the squirrel-assisted seedlings that I transplanted – they have all survived, as well.

I will be traveling, again, this fall, and collecting seeds/nuts along the way (I was in Hibbing this past weekend, and collected walnuts from the one tree that I know of in that city). I do not think the issue was with the way of stratification or storage (seeds were stored in damp saw dust for the winter), but I suspect it was the grow medium and possibly a lack of natural pathogens in soil that the seeds were not exposed to during their emergence?

What should I try differently this fall and spring for the seeds that I collect?

What nutrients/soil-types should I use for a grow medium? Is using a heat-mat advisable?


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I thought I hit all the points that needed to be covered and established a bit of a background on the processes and methods I employed.

Here’s the reply I received:

If some of your nuts grew and survived in the product that you used I wonder if that is the problem. I can’t help but wonder about the maturity of the nuts that you collected. It is possible that some were just not as fully mature when you collected them as the squirrel planted nuts. It is also possible that using a more “squirrel like” method of planting and growing may offer better results. Walnuts that are squirrel planted are frozen all winter, not just chilled. I wonder if you might consider trying a winter seeding approach. Plant your nuts in pots or a row in the garden in the fall and allow nature to provide the proper conditions. You might want to protect the pots or row with chicken wire so that the squirrels don’t eat your nuts. I don’t think a heat mat is necessary. I’m sorry that I can’t give you a more technical answer as to why your success was so limited but I would focus on collecting only fully mature nuts storing in the freezer and trying to reproduce a more natural process. Here is a good link to info about growing walnuts. Good luck! http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/growing-black-walnut/

-Sherry S. MN MG

And, that’s what a Master Gardener had to say about the problem.  I have read the article mentioned in the reply prior the gardener mentioning.  I do agree with the assessment of trying to grow the walnuts more closely to how they grow in nature; letting the nuts freeze, not using a heat mat during emergence, and planting the nuts in the ground outside.  I still suspect something with the grow medium.  It’s not completely valid to say that walnuts prefer richer soils than oaks, and that, that some how explains why the walnuts died and the oaks did not.  But, using methods that are more align to nature but adding that extra edge over nature without coddling too much – chicken wire or fencing to prevent predation of nuts that are planted in the ground, in RootMaker pots, seems to be the way I will go for this next grow season.