“From little acorns mighty oaks do grow”
— American Proverb
This is the perfect time of year to collect acorns to start growing new oak trees over the winter. Acorns that have dropped earlier in the fall are usually the weaker or worm infested seeds. Late dropping acorns (October and November) are typically healthier.
A healthy acorn specimen suitable for growing an oak tree is one that is plump with a cap that is loose and/or easily removed. A naturally split or cracked acorn is fine, but do not collect damaged, crushed or moldy acorns. Avoid acorns with a pinhole on the shell. This is a sure sign that a worm has bored into the nut.
After inspecting the collected acorns, place them in a mixture of ½ peat and ½ loose barley in a clear zip-lock plastic food storage bag. Do not crowd the acorns. Acorns should be loose in the medium and the bag should not be more than ½ full. Seal the bag and store it in the refrigerator throughout the winter. Periodically check the moisture level of the medium. The medium should be damp but not wet. During the winter expect the acorns will split open and white sprouts to appear and grow. This could happen at any time during storage.
In early Spring (Late March to early April) fill individual plant pots with clean potting soil. Place the sprouted acorns horizontally in the soil about 1 ½ inches deep and water. Place the pots in a South facing window or under an artificial light source and keep the soil moist. During the next few weeks, the acorns will sprout into a sapling, with a few tiny, yet visible oak leaves. As the trees grow, transplant them into larger containers. Do not allow the trees to become root bound, or dried out.
You may keep your trees in plant pots indefinitely, or until they have reached a desired size to plant outside. Before planting them in the ground, introduce the trees slowly to the outdoors by placing them in cooler areas such as on a porch or in an unheated sunroom, shed or garage for a few days at a time. Transplant them outside in the early fall before danger of frost.
This post was first published in 2012 and has been updated.