Where to gather acorns

Acorns mature and drop during late summer and early fall, from September to December. Watch for wildlife gathering acorns as a clue to seed maturity.

Oak trees use the wind to spread their pollen. Because of this, trees can possibly pollinate other trees nearly a half-mile away. The best place to collect acorns is an area with a big isolated group of oak trees of the same species. Individual heritage oaks, such as those you see in parking lots and new developments often don’t produce acorns due to a lack of pollination and other factors.

Select a park, national or state forest or other public area with lots of oaks. Check with park managers about regulations or restrictions that may prohibit collecting acorns. If you collect on private property, be sure to obtain the owner’s permission before entering to collect seeds. California has explicit laws about gathering plant materials and it is important to remember that these regulations are designed to protect both plants and wildlife species.

Try to collect acorns from trees growing close to where you intend to plant the new trees. This will ensure that the oak stand will have new members that are genetically related to each other and are adapted to the environmental conditions of that site. Gathering acorns from an area with both native and not native oaks is not recommended because your acorns may produce hybrid trees. There is no way to tell if your acorns are hybrids by looking at them. Hybrids can have unexpected and negative impacts on wildlife and native tree populations.

Once you have identified a location for gathering acorns, plan a trip to collect enough seeds to carry out this project. Providing students with a first-hand experience to view oaks, gather and test acorns and conduct other investigations will help build their knowledge, understanding and appreciation of oaks.

Gathering acorns

Pick the acorns directly from the trees or gather them from beneath the tree’s canopy. Place a tarp below the tree’s canopy to catch acorns as they fall. Use a long, slender stick or branch to “beat” ripe acorns from high above. Alternately, you may throw a rope over a branch and pull on it carefully to shake the branch. These are easy methods for gathering acorns and will not harm either the tree or the acorns.

Choose firm, plump acorns without cracks or holes. Healthy acorns will look shiny, not dried out and won’t rattle if you shake them. Ripe acorns will fall easily out of their caps. Take only a small portion of what you find. Leave enough for the wildlife to use. In many cases, jays, woodpeckers, and squirrels are also busy gathering acorns. Some of these seeds become new oaks, too.

Assessing acorn viability

Not all acorns will be healthy. Some may not be completely formed or may have insect damage. Visually inspect the acorns for holes. Pinholes may indicate insect activity inside. These acorns may still grow, but may not be as healthy or have as much stored energy to help them sprout. Squeeze the acorns to make sure they are solid and shake them to ensure they don’t rattle. Squishy and rattling acorns may be dissected to explore what is wrong with them.

Acorn “Sink & Float”:

The acorn “sink & float” test can be an easy way to sort a large quantity of acorns quickly. Be cautious about using this test prior to storage as it may stimulate early germination and increase mold problems. Hand sorting is preferred for acorns that will be stored in the refrigerator for several months.

Place acorns in a large container and cover them with water. Immediately remove any acorns that float. Save the “floater” acorns for further investigation.

Allow the seeds to soak for at least 12 hours. Remove seeds that have floated to the top of the container.

Drain off the water and plant the “sinker” acorns in containers or directly outdoors.

Using the “floater” acorns, ask students to propose hypotheses about what may have caused these seeds to float. Allow students to dissect the seeds to investigate their contents. Ask them to record their observations about the squishy, rattling and “floater” acorns in their journals.

Storing acorns

After collecting and assessing the viability of the acorns, either plant them in growing containers or in their natural habitat. You may delay planting and keep the seeds in cold storage for several months. Acorns may be stored for up to four months as long as there is stable moisture and cool temperatures. A Ziploc plastic bag makes a great storage container. Store only healthy acorns.

Follow these steps:

1. Separate different species into separate storage bags.
2. Label each bag with the date, specific collection location, and type of oak.
3. Fill the bag no more than halfway with acorns and add 2-3 cups of vermiculite. Potting soil may be used if vermiculite is not available, but should have 2-5 tablespoons of water added prior to storage.
4. Check your acorns every few weeks. If it is wet inside the bags and mold begins to form, wash your acorns with water and repackage in fresh, dry vermiculite.

Planting your acorns

Plant your acorns from late October to the end of February.

When students participate in the decision-making about the acorn planting, they will want to take a greater role in the care and stewardship of the trees, so the class should participate in the site selection process. Choose a sunny spot where the soil is loose and puddles don’t form when it rains. Do not plant your seedlings close to buildings, the sidewalk, driveways or other immovable objects. Also be sure your trees won’t touch any power lines when they grow up. Think back to the size of the oak trees where you gathered your acorns to get an idea of their eventual size.

Take the students to visit the proposed tree-planting site before the event. Review the benefits trees provide, especially to urban environments. Encourage students to imagine how the new trees will change the site. You may want to choose names for the tree (or the grove of trees) planted.

Help your students make pledges to take part in caring for the new trees. Write tree care pledges on paper cut in the shape of a tree, leaf or acorn. These can be buried when the acorn is planted or worn by the tree planters.

Materials:

• Shovels
• Water
• Acorns (2 per student)
• Milk carton (1/2 gallon) or wire screen and string (one per student)
• Wood chips or straw mulch
• Scissors or garden clippers
• Oak Seedling Adoption Certificate for each student

Procedure:

For each student:

1. Dig a hole about 10 inches deep and 6 inches wide, setting aside the removed soil to reuse. Use either a milk carton, with the top and bottom cut off, or the wire screen to make a little house for your acorns. This will help protect them from hungry animals. The wire or carton should touch the bottom of your hole and will be below ground level when you are finished planting.
2. Fill the hole almost to the top with the soil you set aside. Make sure to keep big rocks and grass out of your acorn house. Gently place two acorns on top of the soft dirt floor of your acorn house. If they already have roots, be careful not to break them.
3. Cover the acorns with ¾ inch of soil. Carefully water the inside of your house two times. Make sure the acorns stay buried after watering. If you used wire screen for your enclosure, tie the top closed with string.
4. If your acorns are planted in a busy area or a place where lawn mowers are used, make them more noticeable by marking them with stakes 3 to 5 feet tall or use bright marking tape.
5. Distribute the Oak Seedling Adoption Certificates. Read and discuss the responsibility involved in caring for the seedlings. You may want to read the pledge together and then have each student sign his/her certificate.
6. Check your acorns often. Within 1 to 6 months, you will be able to see your seedlings pushing up through the soil. Acorns spend a lot of time growing roots before they send up a shoot, so be patient. If you have more than one tree growing in each house, wait for them to get 6 inches tall, and then carefully remove the smaller of the two seedlings. Make sure to clip it just below the soil level so it won’t sprout again.
7. Keep competing vegetation, especially grasses, away from young seedlings. These and other plants rob soil moisture and nutrients. Pull any weeds within 2-4 feet of your acorn house and cover the area with mulch. Make sure the mulch does not actually touch your seedling. If you used a wire screen, keep the enclosure tied until the seedling reaches the top. Once it reaches the top, leave it untied.
8. Water young trees once a month during the dry season. Begin watering one month after the last rain in spring and finish at the first good rain in the fall. Give your seedling 5 gallons of water at each watering. After 3 years, your seedling will not need to be watered anymore.

Planting your own seedlings

October through February is the best time to plant your seedlings.

When students participate in the decision-making about the tree planting, they will want to take a greater role in the care and stewardship of the trees, so the class should participate in the site selection process. Choose a sunny spot where the soil is loose and puddles don’t form when it rains. Do not plant your seedlings close to buildings, the sidewalk, driveways or other immovable objects. Also be sure your trees won’t touch any power lines when they grow up. Think back to the size of the oak trees where you gathered your acorns to get an idea of their eventual size.

Take students to visit the proposed tree-planting site before the event. Review the environmental values trees provide, especially to urban environments. Encourage students to imagine how the new trees will change the site. You may want to choose names for the tree (or the grove of trees) planted.

Help your students make pledges to take part in caring for the new trees. Write tree care pledges on paper cut in the shape of a tree, leaf or acorn. These can be tied to the new tree, buried when the tree is planted or worn by the tree planters.

Materials:

• Shovels
• Water
• Seedlings
• Wood chips or straw mulch
• Materials to mark the planting sites-stakes, ribbons

Procedure:

For each seedling:

1. Dig a hole four times as wide as the container and just as deep. Do not plant trees in holes where the tree will be lower than the soil level. Trees planted lower collect too much moisture around the trunk, which encourages the crown to rot.
2. Roughen the sides of the hole to allow for root.
3. Carefully remove the seedling tree from the growing container. Take care not to harm the delicate root system. If trees have been kept in containers for more than one year, the roots need to be carefully loosened before being placed into the hole. Carefully straighten or cut a circling taproot. If the taproot has been severely damaged, the tree may take several months to recover from the shock of planting and side roots will take on the function of supplying the moisture to the young tree.
4. Position the tree in the hole and refill the hole with the original soil. Carefully tamp the soil down to prevent large air pockets from drying out the roots.
5. Cover the soil layer around the tree’s base with 4-6 inches of mulch and water the tree thoroughly so that the soil will settle around the roots. Make sure that the mulch does not actually touch your seedling. Do not plant trees in very dry or soggy soil. Roots grow well in moist soil where adequate oxygen is present.
6. Mark the tree once it has been planted using three stakes placed around the outside of the root ball. Have students make stakes or protective devices for the new tree. Add ribbons or streamers to call attention to the tree. Most trees will establish the correct growth pattern without additional help.
7. Keep competing vegetation, especially grasses, away from young seedlings. These and other plants rob soil moisture and nutrients. Pull any weeds within 2-4 feet of your acorn house and cover the area with mulch. Make sure the mulch does not actually touch your seedling.
8. Water young trees once a month during the dry season. Begin watering one month after the last rain in spring and finish at the first good rain in the fall. Give your seedling 5 gallons of water at each watering. After 3 years, your seedling will not need to be watered anymore.