You may think the planting season is over. Not for me. I recently planted eight giant red oaks. Or, I should say, potentially giant oaks. I planted eight acorns. I’m hoping at least one will begin growing next spring, and will eventually provide shade, food for wildlife and beauty for all who happen by.
This is the season for planting acorns. They need an extended cold period in order to germinate, come spring. That cold requirement prevents them from germinating now, and being killed off before getting established. Most nut trees, including most oaks, have a tap root that grows deep into the soil. Red oak Quercus rubra), I have read, has relatively shallow roots. Still, if you want an oak, plant your acorns where you want a tree. Don’t move them once they have started growing if you can avoid it.
Here is what I did: Before I planted the acorns, I inspected them carefully to see if there were any signs of insects boring into them, but saw no holes. Then I put them in a bowl of water to see if any floated. Any that float should be discarded, as they are probably not viable. Of the 10 I put in water, two floated and went to the compost pile.
Next, I went outdoors to plant. I looked for a place where a young oak would get plenty of sunshine — six hours a day is adequate — and where a big tree would not be competing with other trees. According to my favorite tree expert, Michael Dirr, a mature red oak will grow to be 60 to 75 feet tall and nearly as wide at maturity. I did not have an area quite that wide to dedicate to an oak, but I found a spot where it will fit between two maples along my property line.
Oaks do well in well-drained, acidic soil. Red oak, because it has a relatively shallow root system, can be prone to drying out when the trees are young, so I am prepared to water my seedling until it is well-established if the summer is hot and dry.
I raked off leaves and snow and loosened the soil in a 2-foot wide circle with a hand tool. Then I pushed acorns into the soil and covered each with an inch or so of soil. Then I patted down the soil and covered the area with leaves. I placed a nice metal name plate in the middle of the planting zone with the date I planted the acorns.
If more than one of my acorns grows, I will have to choose the best to keep. Yes, I could keep more than one for a while, but brother and sister trees will compete for sun, water and nutrients, so the extras will need to be weeded out.
If digging in frozen ground doesn’t appeal to you or if the squirrels are watching your every move, acorns can be collected in winter, stratified in a refrigerator for a minimum of 30 to 60 days, and then planted in the spring. Store them in a paper bag in the vegetable drawer to keep them from drying out. By spring, the squirrels will have better fish to fry (like the tender shoots of my hostas).
Red oak nuts may need help opening their shells if they have been stratified, or preserved indoors, because they do not go through multiple freeze and thaw cycles. Simply score the acorn with a knife or rub it with 80-grit sandpaper until the kernel is exposed.
Not all acorns will germinate the first year, which makes sense from a Darwinian point of view: If a drought or a forest fire kills off some seedlings this year, others will be able to pop up the next.
One of the best oaks for suburban areas is the pin oak (Quercus palustris). It is smaller than many oaks (still, it grows to about 60 feet), with shallow fibrous roots that can thrive in the heavy clay often found in the disturbed soil of subdivisions. It prefers acidic soils, so it does well in the Northeast.
Pin oaks grow more quickly than many oaks, often adding 2 feet of height or more per year, and they have a profile that is handsome year-round. Like all the oaks discussed here, they are hardy in Zones 4 to 8 or 9.
The white oak (Quercus alba), is majestic and can live 500 years or more, attaining heights of 100 feet. It does best in deep, moist, well-drained soils. It is susceptible to anthracnose and other diseases, but thrives in the wild from Maine to Florida and as far west as Minnesota and Texas. It is worth planting where space permits.
The chestnut oak (Quercus prinus) is handsome, with deeply furrowed bark and a nearly globe-shaped form that is striking in winter. It can survive in dry, rocky places that would be eschewed by other trees.
Being a gardener means, among other things, being optimistic. Having a long view. And being a little silly — after all, surely most people seeing me digging in the frozen soil would consider me a bit daft. I don’t care. Planting acorns in winter is more fun than sitting at a computer any day.
Henry may be reached at firstname.lastname@example.org. He is the author of four gardening books and lives in Cornish Flat, New Hampshire.