Red oaks need to go through a cold period before sprouting, which is called cold moist stratification, whereas white oaks do not.
Red Oak (Quercus rubra)
Acorns mature over two growing seasons. Seed dispersal is from end of August until early October, with a mast year every 1-3 years also referred to as bumper crop. They can be distinguished by their sharp, pointed lobes in their leaves with bristly tips.
Choosing the right tree from which to collect your seeds
will have a huge impact on how resilient our landscape will be in 100 years.
It is best to observe the biggest, oldest, healthiest and most beautiful trees in your neighbourhood over the seasons and figure out a strategy on how you could collect their seeds when it is the right time. E.g. establish a relationship with the owner of the property.
If you already know where your future trees will be placed, find a tree that has similar growing conditions regarding soil structure, moisture content, wind and sun exposure.
To be able to collect ripe and healthy acorns you need to keep a close eye on your tree starting fall. We are racing with squirrels, chipmunks, and blue jays who are experts. Watching them can help us to get the timing right.
When you collect your seeds make sure to write the location, the tree, and the date on the batch. Always add this information to anywhere the seeds go. That way you can trace the origin of the sapling up to the permanent site. This information is important to match the right trees to the growing conditions of your site.
Any potting soil works well,
the finer the better.
Potting soil with mycorrhizal fungi can make it easier for the plants to uptake nutrients.
All containers must have enough holes to drain excess water. Most important is the hight of a container to allow for a healthy root development. 2l milk cartons, 2l plastic beverage bottles, any potting containers and raised beds can be used. Those keep the moisture level for a long period of time.
Biodegradable and cloth pots have benefits, environmental impact and better root development but dry out faster.
All saplings benefit from enough sunlight.
Collect seeds as soon as you hear them start to drop. Squirrels find the good ones quickly.
It's best to collect them in plastic bags because they lose viability, meaning their ability to sprout, very fast when they dry out. Once home plant or cold store them immediately.
Oaks are a powerful contributors to functioning, healthy ecosystems. Therefore a lot of the acorns will have been eaten by weevil larvae which will develop into a beetle. To separate the viable acorns
fill a container with water,
add the acorns.
Acorns that sink to the bottom are likely to be viable.
Return floating acorns to nature.
Perform this float test and soak them for 24 hours before stratifying or planting.
Stratification For Indoor Planting
Cold-moist stratify acorns for 3 to 4 months:
moisten 2 paper towels,
wring them out,
place them in a freezer bag.
Place acorns beside each other in between the layers of the paper towels.
Lay bag with acorns flat in the fridge, not freezer.
Check on them every week or two to make sure:
Paper towels are still moist. If not, moisten again and wring them out.
No fungus is developing. If so, wipe off the fungus and keep them in a separate bag. Keep the paper towels less wet.
Roots are not turning black, if so plant immediately.
Once the root is about an inch long or by mid of February, even if the acorn hasn't sprouted yet, plant them indoors.
Instead of paper towels you can also use a moistened sand-soil mix to store your acorns in the fridge.
Indoor Planting From Late January Until March
Planting the Acorn
Oaks have long tap roots therefore they need a container of at least 20 cm height.
Mid to end of February acorns should be planted even if no splitting or taproot development occurred, if they have been stratified for a minimum of four month.
If the acorn starts germinating before that time and the taproot is about 2-3 cm (1-1.5 inches), it should be planted immediately.
Find a container that is at least 20 cm (8 inches) tall, since the root of an 8 month old oak sapling can easily be a foot long (30 cm).
Cut off the corners or make holes in the container for drainage.
Moisten your potting soil throughout. It can take time for the soil to absorb the moisture and can be done a day ahead.
Fill the container with potting soil.
Tap the container to settle the soil.
Add more soil.
Repeat this process until the container is filled until 1cm below the rim.
Create a small indent with your finger.
Place the acorn sideways into the dent. The root and the sprout come out from the same place therefore it is important to plant the acorn lengthwise.
Press the acorn gently in that two thirds of the acorn are submerged in the soil and one third is on top of the soil.
The root develops first. If a root has developed the root has to point downwards still keeping the acorn lengthwise.
Place in a sunny window.
Keep the soil moist but not wet.
Watch carefully, it is amazing how fast the shoot emerges.
Keep the sapling inside until mid of April.
Taking Saplings Outdoors
In April, weather permitting, start taking your saplings outdoors to harden them off. Start with taking them outdoors in the shade for one hour and bring them back inside.
Increase the time they are exposed to the outdoor light every day for about an hour.
After a week, also put them in morning or afternoon sun and gradually expose them to the intense sunlight around noon.
After two to three weeks and once the danger of frost has passed leave them permanently outside.
Their leaves might get sunburned and they might even loose their leaves but they will grow back.
You can transplant them into raised beds, into a permanent home or leave them in the pot they are growing.
Oaks develop extremely long taproots to store nutrients and energy as well establish intricate and mutual relations with the microbial environment of the soil. The older the sapling the more difficult it is to lift it without injuring the tap root. No research has been done on the long term effect of severed taproots. Therefore it seems plausible, if you can protect the small sapling from rabbits and deer, it is best to transplant oaks into their permanent home in late fall of the same year they germinate. This will allow for optimal root development and gives the tree a chance to become a healthy tree that can thrive for hundreds of years.
Outdoor Planting in May or Fall
If you intend to transplant your oaks, you can build a raised bed with a minimum hight of 50 cm to accommodate the long tap roots.
Fill the raised bed with soil.
Place the acorn sideways onto the surface.
Press the acorn into the soil that two thirds of the acorn is submerged in the soil and one third is on top of the soil.
Label your acorns with the tree species, the location of the mother tree, and the date it was planted. Cut-up yoghurt tubs work well as signs. To make the signage winter proof, coat it with tape.
Cover with a layer of leaves.
Secure with small holed chicken wire, hardware cloth or sturdy mesh right away to protect the acorns from rodents.
Keep soil moist until snow covers it.
You can also just plant them in their permanent location with rodent protection.
Caring For Your Sapling
Keep your soil moist from spring until the first frost.
In spring: add some compost on top of the soil to enrich it with nutrients that will help to keep your sapling healthy and growing. To add compost, pull the leaves aside, add compost directly onto the soil and then cover the compost with leaves so the nitrogen in your compost doesn't escape into the air and that the soil retains moisture longer. No need to mulch with wood chips if you can maintain a good leaf cover. If not, use natural un-dyed wood chips as mulch.
Ongoing: make sure that the trees have enough space to grow their roots into the soil and that the stem, branches and leaves get enough space and sun. Other trees and some well behaved plants can be beneficial close to the saplings but make sure they don't get crowded out or overrun by aggressive plants. Experiment with what companions are beneficial to your trees. You can observe which plants grow together in natural areas.
In fall: add more leaves to create a 3 inch cover and keep watering until the first frost.
It is important to leave at least 30 cm of tap root intact. It can be cut anywhere after the 30 cm mark. If your trees are grown in a raised bed, you can take off planks from one side and cut the roots from the front.
Trees best transplant before they leaf out in spring or after they have lost all leaves in fall. If you transplant the tree into an area where watering is difficult, fall is the best season to transplant since the tree has more time to grow a root system without having to use up energy to produce leaves, flowers and fruits. There is less stress on it because the weather stays cool and there is an increase in rainfall. Keep the tree well watered that fall and the next spring.
As we discussed in the introduction it is important to match your sapling with its preferred growing conditions.