Stratification of Seeds

Bill Devlin
Adams County Master Gardener

Fall is here. It's time to think about, or better yet, to act on renewing our environment. The best part of Pennsylvania is that it's truly Penn's Woods. Three hundred years ago it was nearly all woods, now there are fewer and fewer trees, as agriculture and urban development are the order of the day. We can mitigate that situation by planting trees. Planting trees can be expensive - it doesn't have to be; it can be nearly free through the miracle of stratification. Well, maybe miracle is a little much, but the first time you try it and it works, it feels like a miracle.

What is stratification? Stratification is artificially overcoming a seed's dormancy by placing it in layers of moisture-retaining media (paper towel, potting soil, etc.) and keeping it under generally cool and moist conditions for a period of time. This will simulate winter conditions, according to the Garden Web Glossary of Botanical Terms (

Now that we know what stratification is, let's get down to cases. Our forefathers created magnificent parks by planting or saving slow growing, huge trees like Oaks, Hickories, and Walnuts. We should be doing the same for our grandchildren and our grandchildren's grandchildren. That is how long a white oak can take to reach maturity.

So, the recipe is to get out into the woods on these magnificent fall days and look for the kind of trees we would like our progeny to have. Collect some large acorns, walnuts, hickory nuts, or whatever, and bag them. Particularly the walnuts, they can be very messy.

When you get home, seal them in a plastic bag with a moistened piece of paper towel, and put them in the refrigerator. Real gardeners have a second refrigerator in the basement or garage. If you don't, ask around, I will venture lots of your neighbors do.

If you don't have any luck with locating a refrigerator, another method is burying them temporarily in an area where you can control access from the varmints. Dig a hole about a spade depth deep and partially fill it with clean leaves, sawdust, shredded newsprint, or similar moisture-retaining material. Mark the spot so that you can dig them up and replant in the spring.

When spring rolls around, you should have planned where you want these magnificent trees to be. Prepare the ground and mulch an area a couple of feet in diameter-well marked so the seedlings won't be accidentally be mown down.

Why not just stick them in the ground? Several reasons: squirrels, mice, voles, and moles to name a few. My success with this method has been a big, fat zero. My success with the recommended method above has been over 90%.

If you don't have a place in mind to plant the trees right away, you can still get the ball rolling for later transplantation. If you don't have space for these large trees but like to dabble in horticulture, work with your local parks authority, which may be looking for donated trees.

Large seeded trees are generally taproot varieties, thus transplanting can be very problematic unless you have a scheme. My scheme is to start the stratified nuts in tubes that allow for a two-foot root to develop without danger of damaging the root, and thus killing the tree, at transplant time.

I cut about a 2' length of 6" flexible corrugated plastic drainpipe, fill it with some potting media - either commercial or topsoil mixed with mulch, etc., and stand in a shorter container that can be kept moist. For example, I currently have a fiberglass basket about 18" deep filled with 9 tubes of pecans. The pecans are both refrigerator and direct burial stratified, and are doing quite well. With the West Nile virus scare, I have a thin film of clean transmission oil on the surface of the water to discourage mosquitoes. If you email me at, I will be glad to email some pictures of my activities in this area.

The Adams County Penn State Master Gardeners report public contacts on an annual basis. In order to determine our success in reaching out, I would appreciate an email notification telling me how many in your household read and appreciated this article. Please address the email for this article to Bill Devlin,

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