Growing Oaks From Acorns: 7 Home Experiments Worth Learning From

Growing an oak from an acorn is one of the cheapest and most satisfying tree projects there is, and also one of the easiest to get slightly wrong. We read through accounts from gardeners who actually tried it, from a single pot on a windowsill to a family that germinated hundreds, and picked seven that show the steps and the surprises.

Each entry links to the original post. The photos on this page are illustrative stock images from Wikimedia Commons, credited under each one. They are not photos of the bloggers’ seedlings. For the full method, see our guide to growing oak trees from acorns.

1. American Forests: An office windowsill full of red, willow and bur oaks

From Lea Sloan, American Forests: The acorn experiment (original post)

Lea Sloan, who works at the conservation group American Forests, collected acorns from red, willow, bur and pin or scarlet oaks around Washington, D.C. She floated them, kept the sinkers, and chilled them in labelled bags of damp sphagnum and vermiculite in the fridge. By February some red oak acorns had already sprouted roots, and the seedlings soon outgrew their small pots.

Her candid note about timing is the lesson: she planted too early, then had to hold the seedlings in small pots while winter dragged on. Oak taproots grow fast, so it pays to have deep pots ready before the roots appear. Her follow-up post describes giving the young trees to neighbors who promised to water them for two summers.

2. Gretchen Ronnevik: A child's project that turned into hundreds of seedlings

From Gretchen Ronnevik: Acorns Part 2 (original post)

Gretchen Ronnevik’s son collected hundreds of acorns. After the float test, the family packed them in bags of wet wood chips and filled a whole fridge shelf. When the shells began to crack, they planted 126 germinated acorns in cheap paper cups on the advice of a master gardener relative, and set them in a cool, bright, drafty entryway.

Two practical points stand out. Some bags developed white fuzz and a bad smell, so check stored acorns regularly and throw out moldy ones. Paper cups are a fine low-cost start, but oaks need deeper containers soon after. The post is also simply a lovely account of saying yes to a big, messy project.

3. Toronto Gardens: Starting with fresh acorns and the float test

From Toronto Gardens: Growing An Oak Tree From An Acorn: Part 1 (original post)

Inspired by entomologist Doug Tallamy’s point that oaks support more caterpillar species than almost any other tree, this Toronto writer collected six or seven acorns on a ravine walk. Three sank in the float test, and they were the greenest ones. The floaters were brown and had probably been lying around longer, leaving them open to weevils.

Fresh, green-brown acorns collected soon after they drop germinate best, a point a commenter on the post backs up with advice from tree expert Michael Dirr. If you only gather a handful, pick them straight from under the tree rather than from old leaf litter.

4. The Archerland Homestead: A small side-by-side test with and without plastic wrap

From Archerland, The Archerland Homestead: Let's (Attempt To) Grow A Tree Together! (original post)

This Minnesota homesteader gathered acorns from a local park, discarded the floaters, and planted two acorns per small container of seedling mix. As a small experiment, half the containers were covered with plastic wrap to hold moisture and half were left open.

Planting two per pot and thinning to the stronger seedling later is a good hedge when germination is uncertain. The covered-versus-uncovered test is worth copying too: acorns dry out easily, and a dried-out acorn will not sprout. Just watch covered pots for mold.

5. Garden Experiences: A valley oak from a parking lot, 46 years on

From David Ross, Garden Experiences: Mighty Oaks from Little Acorns (original post)

In 1976 David Ross collected valley oak acorns in a California shopping center parking lot and sprouted them right away in damp peat moss, since his mild, rainy winters did the job a fridge would do elsewhere. He moved the seedlings up through quart, gallon and five-gallon pots, trimming the taproot each time so the root system would spread and adapt to garden watering.

Forty-six years later the tree is taller than his two-story house, with a trunk over 2 feet across and branches spreading about 70 feet. That spread is the real lesson: an acorn grows into a very large tree, so plant it well away from the house. Our guide to how close to a house you can plant an oak covers the distances.

6. Our Maker's Acres Family Farm: A live oak grown from an Alamo acorn

From Kyle Sonnier, Our Maker's Acres Family Farm: Planting the Anniversary Oak (original post)

Kyle Sonnier and his wife germinated a handful of live oak acorns from the Alamo in San Antonio, where they got engaged. One sprouted, and by the time it was about 3 feet tall they planted it in the lowest, dampest part of their yard, near the pasture, with a soil berm to hold water and daily watering until the rain came.

Choosing the planting spot for moisture in drought, and keeping a hose within reach, is exactly right for a young oak in its first summers. Live oaks spread very wide, so an open spot like this, away from buildings, suits them. And sometimes a tree is worth growing for the story alone.

7. The Futile Garden: Southern red oaks rescued into deeper pots

From The Futile Garden: Faith in a Seed (original post)

This gardener potted acorns in fall from a big southern red oak in the front yard, plus some from a creek that the writer thought might be pin oak. By February, white roots were coming out of the bottom of the pots. She moved eight sprouted acorns into deeper homemade “tree pots” cut from plastic creamer containers and set them in a south window. A bur oak acorn from the writer’s sister had not sprouted yet.

Roots out of the drainage holes are the classic sign that oak pots are too shallow, and repurposed tall containers are a clever, cheap fix. As for the bur oak: Iowa State Extension says bur oak acorns need 30 to 60 days of cold, moist stratification, longer than red or pin oaks, so a slow bur oak may just need more time in the cold.

What these experiments teach

The same steps come up again and again: collect fresh acorns, float them and keep the ones that sink, give red-oak-group acorns a cold, moist spell in the fridge, and plant them in deep pots before the taproot gets long. Iowa State Extension notes that white oak and swamp white oak acorns should be planted in fall, while red and pin oaks need 30 to 45 days of cold stratification and bur oak 30 to 60.

Then comes the part several of these gardeners mention: water the young tree through its first two summers, and plant it where a very large tree can grow. For timing, see the best time to plant an oak tree.

Top photo: Dominicus Johannes Bergsma, CC BY-SA 4.0, via Wikimedia Commons