The Date to Collect Ripe Acorns for Planting:
Beginning as early as late August and continuing through December, various species of oak acorns are maturing and ripening for collection. Ripening dates vary from year to year and from state to state by as much as three to four weeks, making it difficult to use actual dates to determine maturity.
The best time to collect acorns, either off the tree or from the ground, is when they begin falling - just that simple. Prime picking is late September through the first week in November, depending on oak tree species and location within the United States. The acorn is perfect when plump and the cap removes easily.
Collecting Acorns for Planting:
The height of the acorn crop above and the forest litter below can make it very difficult for the causal collector to gather large numbers of acorns in a forest setting. Lawns or paved areas help in collecting acorns if trees are found and prepared before site conditions degrade the nut.
Locate open grown trees that are heavily loaded with acorns that are in or adjacent to parking lots such as at churches or schools. Trees chosen in this way also make identifying the acorns easier. Always identify the tree and place tags or mark the bags so you will know what species you have collected.
Preparing Acorns for Planting:
The two most critical components for caring for acorns that are to be planted are: not allowing the acorns to dry out for an extended period and not allowing the acorns to heat up. Acorns will lose their ability to germinate very quickly if allowed to dry out.
Keep acorns in the shade as you collect them, and put them in your refrigerator as soon as possible if not planting immediately. Don't freeze acorns.
Immediate planting should be limited to the white oak species group including white, bur, chestnut and swamp oak. Red oak species group acorns must be planted in the second season - the following spring.
Storing Acorns for Planting:
Put acorns in a polyethylene plastic bag - a wall thickness of four to ten mils - with damp peat mix or sawdust. These bags are ideal for storing acorns since they are permeable to carbon dioxide and oxygen but impermeable to moisture.
Close the bag loosely and store in the refrigerator at 40 degrees (white oaks can still sprout at between 36 and 39 degrees). Check acorns throughout the winter and keep just barely damp.
Red oak acorns need about 1000 hours of cold or about 42 days. Planting these acorns in late April of the following season gives you the best success but can be planted later.
Planting White Oak Group Acorns:
White oak acorns mature in one season - the season of collection. White oak acorns do not exhibit seed dormancy and will start to germinate very soon after maturing and falling to the ground. You can plant these acorns immediately or refrigerate for later planting.
Planting Red Oak Group Acorns:
Red oak acorns mature in two seasons. The red oak group has to have some seed dormancy and generally does not germinate until the following spring and with some stratification (a cooling period). If stored properly and kept damp, these red oak acorns can be held in cold storage for planting in late April through early summer.
Germinating and Potting Acorns:
After determining the proper time to plant, you should select the best looking acorns (plump and rot-free) and place those in loose potting soil in one-gallon pots or deeper containers. The tap root will grow quickly to the bottom of containers and root width is not as important.
Containers should have holes in the bottom to allow for drainage. Place acorns on their sides at a depth of one half to one times the width of the acorn. Keep the soil moist but aerated. Keep the "pots" from freezing.
Don't allow an oak seedling’s tap root to grow out of the container bottom and into the soil below. This will break the tap root. If possible, seedlings should be transplanted as soon as the first leaves open and become firm but before extensive root development occurs.
The planting hole should he twice as wide and deep as the pot and root ball. Carefully remove the root ball. Gently set the root ball in the hole with the root crown at the level of the soil surface. Fill the hole with soil, firmly tamp and soak.