Collect acorns in the fall and if you want to wait until late winter or early spring to plant them, you'll have to preserve them properly in the meantime. Otherwise, they may dry out, rot or sprout too early. To increase the likelihood of a successful planting, collect acorns from oak trees that are native to your area. Also, acorns found on the ground may contain insects, so lay a piece of plastic or a sheet on the ground and tap the tree with a long stick or pole. The acorns that drop onto the plastic or sheet are likely to be good ones for preserving.
Remove any debris with the acorns, such as sticks and rocks, and take off the acorn caps by twisting them off. Discard acorns that have holes or cracks.
Fill a bucket with 1 gallon of lukewarm water and 1/2 cup of bleach. Place the acorns in the bleach water and stir. Discard the acorns that float and drain the rest in a colander. Lay them out on towels to air dry for a couple of hours. You do not need to soak the acorns for any specified amount of time. This step is simply to disinfect them quickly and see which ones float.
Place the acorns in sealed plastic bags. Don't store more than 3 cups of acorns in any one bag. They will produce too much heat.
Store the bags in the refrigerator until planting time. Check on the acorns periodically to check for mold. If there is mold, clean them again in bleach water, rinse, dry and place them back in storage. Note that acorns will only store for a few months, so plant them in the late winter or early in the spring.