It only takes an acorn to grow a majestic oak tree. For an easier start, however, you can purchase an oak tree sapling at the garden center. Two of the most common oak trees are the red oak and the white oak. Care instructions for your oak tree vary depending on the variety. To determine which type of oak you are harvesting acorns from, study the leaves. The white oak has smooth leaves with no bristles on the leaf lobes. The red oak has bristles on its leaf tips and lobes. Make sure you follow the specific care instructions for your type of oak.
Step 1 - Collect Acorns
Gather acorns from the ground beneath an established oak tree in late September to early November. Acorns should be plump without splits or rotting. [Acorns are ready to be planted when the cap loosens and is removed easily.] White oak acorns can be planted immediately, but red oak acorns need to be stored until the following spring.
TIP: Our expert gardening advisor, Rachel Klein adds, "You may find white acorns on the ground that have already started to sprout. You can gently harvest these little sprouts and plant them immediately."
White oak acorns mature and germinate in one season while the red oak acorns take 2 seasons to mature. This means that the red oak acorns will need to be stored and planted next spring. With the right storing conditions red oak acorns stay dormant until germinating the following spring.
Step 2 - Store Acorns
If you need to store your acorns before planting, the most important storage tip is to keep the acorns moist. If they are allowed to become dry, the acorns may lose their viability. Place oak acorns in a plastic bag with damp peat moss, saw dust, or peat mix. Close the bag loosely and put it in a refrigerator set to 32 to 40 degrees F. This cooling period is very important for red acorns. Never freeze your acorns. Check acorns throughout the winter to ensure that they are still slightly damp.
Red acorns need at least 42 days of a cooling dormancy period to become viable. This means you want to aim to plant your red oak acorns in late April. Acorns can be planted later in the spring if need be.
TIP: Rachel notes, "You can store white acorns in this fashion if you need to delay planting. However, you need to keep the temperature at 32 to 35 degrees F. White acorns will sprout given temperatures between 36 and 39 degrees."
Step 3 - Plant Acorns
Choose your plumpest and healthiest acorns. Make sure they are free of fungus or mold of any type. Fill 1-gallon planting pots with potting soil. Never use garden soil. It could be infected with pests, fungus, or disease. You can also use a larger pot. Keep in mind that your oak's vertical tap root grows very quickly. The length of a pot is more important than the depth. Place acorns on their sides into the soil. Loosely cover each with soil and water. Keep the soil moist but never soggy. Soil should never be allowed to dry. Pots should have drainage holes and be resistant to freezing.
Step 4 - Transplant Seedlings
Choose a spot that will accommodate a full grown oak. This mature size will vary depending on the type of oak. Do not plant your seedling too close to structures, streets, or sidewalks. Your oak seedling is ready to plant when it's first set of leaves seem firm and strong. This should occur about 3 weeks after germination. Dig a hole that is the depth of the pot and twice as wide.
TIP: Rachel recommends, "Inspect the soil. Make sure that it is free from pest infestations and fungus. You don't want to plant your delicate seedling in a hole full of its enemies!"
You can put a few handfuls of organic leaf compost in the hole to give your seedling an extra jumpstart. Remove the root ball from the pot and place it in the hole with the root crown at soil level. Pack the soil into the hole and soak it with water.
TIP: Rachel advises, "As your young oak matures it will expend a huge amount of energy developing a strong healthy root system. While they are growing, however, the roots are very delicate and susceptible to damage. For this reason, take special care to leave the root ball alone!"
Step 5 - Transplant a Young Oak Tree
If you choose to buy an oak sapling instead of growing one from acorn, the planting instructions are slightly different. First, choose a spot that will accommodate a full grown oak. This mature size will vary depending on the type of oak. Again, do not plant your sapling too close to structures, streets, or sidewalks. Prepare a hole a few inches smaller than the depth of the tree’s root ball. Make the width of the hole 3 times larger than the dimension of the root ball. As you would for a seedling, inspect the soil for pest infestations and fungus. Place the root ball in the hole with the root crown at soil level. Fill the hole in with soil, creating a firm mound around the base of the tree.
TIP: Rachel suggests, "Before transplanting seedlings, many gardeners choose to harden off their trees. Hardening off ensures that your oak will be used to the temperatures outside before planting. It will increase the chance of a healthy transplant. To harden off your seedling wait until it has opened its first set of leaves. Then, begin placing the pot outside for a few hours a day in the early afternoon. Each day, gradually increase the amount of time the tree stays outside, moving it into the house or garage at night. After three weeks to a month of hardening off, your young tree is ready for transplant. Hardening off typically works best for seedlings planted in large pots since the roots will have plenty of room to grow during the process."
Step 6 - Water Your Young Oak Tree
Water the oak tree regularly for the first year to establish the root system. Slow watering helps the tree become hardy. Be careful not to overwater, because too much water can cause root rot. The best way to water is with a soaker ball, soaker hose, or a drip irrigation system. Always place the water device a few inches away from the tree. Turn on the hose to a slow trickle and water your young oak for 10 minutes every other day in hot summer weather. As the weather cools down in the fall, gradually cut back your watering to once every week to every 2 weeks. Cease watering in the winter. After the first growing year, cut back waterings to hot days and times of drought.
Step 7 - Protect Your Oak Tree
Use organic mulch to lock in moisture and to keep the soil from becoming compacted. Spread a layer of mulch 2 to 3 inches deep around the tree, taking care not to come in direct contact with the base of the tree. Good types of mulch to use for the oak tree are Aphelia hay, woodchips or pine needles.
Remember to protect your young oak from weather conditions, animals, and equipment damage. There are many different types of tree guards, each one specializing in different kinds of protection. Choose one based on what problems you experience or foresee with your oak sapling.
TIP: Rachel adds, "To learn more about the different types of tree guards, visit this article!"