How To Plant Acorns And Grow Oak Trees

• Determine if your acorn comes from a Red or White Oak type tree
• Remove the cap and inspect for holes, see if it sinks in water (viability test)
  • Only acorns that sink in water are viable (see why here)
• Acorns from the White Oak type trees can be planted immediately 1-2″ deep in pots or in the ground
• Acorns from the Red Oak type trees need to be cold stratified or winter sown (in a garage) for 60-120 days depending on the specific species before they will germinate
• Acorns planted directly in the ground need to be protected from squirrels
• Oak saplings need to be protected from both squirrels and deer

Determine the type of Oak tree – Red or White

An important piece of information you need before you plant your acorns is to determine what kind of Oak tree you have. You don’t need to know the exact species, but you should know whether it is from a Red or White Oak tree.

The easiest way to tell the difference between the two is to look at the tips of the leaves. The leaves of red oaks will have pointed tips, while the leaf tips of white oaks are rounded. Below you can see side by side images of a ‘Red’ oak tree and white oak tree. Notice the lobes on the leaves – red oaks have pointed tips, while white oak have rounded^[1][2].

It is important to note the difference as “Red” type oak trees must experience a long cold-moist period before they will sprout. While “White” oak acorns will germinate in cool temperatures when exposed to significant humidity.

Harvest your acorns

You need to gather your acorns at the proper time. If you harvest your acorns too early the embryo inside may not had sufficient time to develop. On the other hand, if you wait too long to harvest your acorns, the squirrels will have planted or eaten all the viable acorns, and the only ones left likely have weevil damage and will not germinate.

Timing

So, when should you gather acorns to germinate them? Simple – wait until they begin to naturally fall from the tree. Once this begins, you can gather them shortly after they hit the ground. Or, if you are certain a tree is starting to drop it’s acorns, then you can pull them directly from the tree.

The time of year when Oak trees begin to drop acorns naturally is generally late summer to Fall. I live on the border of zone 6 and 7 in Southern Pennsylvania, and this usually occurs in September or October. They may drop sooner or later depending on where you live.

The method I use, is if I find an Oak tree I want to collect acorns from, I just monitor it weekly starting in late August or early September to see when they fall naturally. Different species droop acorns at different times, but those times often overlap. So if you notice one tree dropping acorns, it is likely that the tree you are interested in is probably doing so too, or about to do so.

Are last years acorns ok?

When you go near oak trees, you will often see a plethora of acorns on the ground at any time of year. Outside of late summer or early fall, these are mostly dark brown or black, and may crush easily.

Unless it is late summer or fall, the acorns you are seeing are from the prior year and are not viable. The fact that no deer nor squirrel has eaten the acorn testifies to the fact that the embryo isn’t there, has been consumed by larvae, or is dead.

Inspect acorns for holes

Once you’ve gathered your acorns, you need to remove the cap and inspect them for holes. Do not disregard this step, as it is incredibly important to making sure your acorns are viable and can germinate.

To remove the cap, try to just twist it off with your hands. If that doesn’t work, a bottle opener or twisting a screwdriver underneath can work too. After the cap is removed, carefully look over the acorn for any holes. Holes in acorns are made by insect larvae that burrow through the shell to eat the embryo inside. And as you can probably guess, this makes the acorn non-viable. So, discard any acorns that have holes.

Float test the acorns

One final test for acorns is to float them in water^[3]. Now, there has been some controversy as to the effectiveness of this test, but I find that it is helpful. It takes me almost no time to do the test, and it just further confirms that I will plant viable acorns.

Some studies have found that inspecting acorns for holes (by itself) is more effective than doing the float test alone^[4]. However, in the next section we are going to soak our acorns for 24 hours to help keep them moist before sprouting or stratifying them, so the float test is sort of going to be done anyway.

But, if you want to read up more on the float test, I’ve summarized the scientific literature here.

Storing viable acorns

Acorns that do not have holes and sink in water are considered viable. They can be stored in the fridge for a time before planting. Do not leave them out at room temperature, as they will dry out and the embryo will die.

Germinating White Oak type acorns

In nature, White Oak acorns sprout shortly after falling to the forest floor. The shady environment of a forest helps keep the ground moist, and thus with constant access to humidity/moisture they sprout their root. This root then pushes it’s way deep into the soil, 9-12″ before Winter sets in. The acorn (and root) will then sit on the forest floor under leaves until something eats it, or Spring when the upper stem and leaves will emerge.

Some common types of ‘white’ oak trees would include Burr Oak, Chestnut Oak, White Oak, and Swamp White Oak.

But, if you wish, you can directly sow fresh white oak type acorns where you want a tree to grow. Just plant them 1-2″ deep, and don’t let them dry out. You will need to prevent squirrels from digging them up during the winter though. I would recommend hardware cloth weighed down with rocks.

Sprouting white oak type acorns

If your acorns are from the White Oak Group, then to sprout them you just need to get them in contact with a moist medium. The easiest way to do this is to fill a container with moist sphagnum peat moss and sand, or even just regular potting soil. The soil or moss should be thoroughly moistened so that when you squeeze a handful, only a few drops of water fall out. Then just press them into the surface. Finally, place the container in the fridge.

Alternative you can use moist paper towels to do this as well. To do this simply line the bottom of a Tupperware or waterproof container with several moist (but not wet) paper towels. Then, place your acorns on the bottom, leaving a bit of space between them. Finally, cover with several more moist paper towels and place the container in the fridge.

You need to check your acorns every other day to make sure the paper towels stay moist, and to see if they have sprouted. Any acorn that begins to sprout can be planted.

Germinating Red Oak type acorns

Acorns from the Red Oak type have a dormancy mechanism that prevents them from sprouting until Spring^[5][6]. In nature, red oak group acorns will not sprout until Spring, after they have sat in the moist soil or under leaf litter all winter long, where they are cold and moist but not freezing. We must simulate or expose them to similar conditions either by cold moist stratification or winter sowing. Before I go further, I must say that I find the easiest method is to winter sow.

The most common types of Red Oak trees in Eastern North America would be Pin Oak and Northern Red Oak.

Winter sowing red oak type acorns

To winter sow red oak type acorns, simply plant them 1-2″ deep in a suitable container filled with moist potting soil. Then, place it in a cold location that is protected from squirrels. If your area is prone to freezing conditions, then I recommend you to place the containers in an unheated garage or shed. Otherwise, outside along the north side of a structure is fine.

Cold stratifying red oak type acorns in the fridge

Alternatively you can cold stratify red oak type acorns in the refrigerator. To do this fill a large ziplock bag with moist sand or a mixture of sphagnum peat moss and vermiculite. It should be moist enough where if you squeeze a handful only a couple drops of water fall out. Place the acorns in the mixture, so they are mostly surrounded, then seal the bag and leave it in the fridge for 120 days.

How to plant an acorn

Planting sprouted white oak acorns

To plant acorns, whether sprouted white oak type or red oak type, the process is the same. For acorn planting depth, place them 1-2″ deep in a 9″ container filled with moist potting soil, or directly in the ground protected from squirrels.. For this step you will need a suitable container and moist potting soil.

And regarding whether you should plant an acorn pointed up or down, don’t worry – just place it on it’s side. Press it firmly into the dirt, and bury it 1-2″ deep.

You can plant more than one acorn per container. If you wish to separate them later, you can do so, but you must do it not long after the true leaves unfurl. And, as you would expect, you need to be incredibly gentle. See the next two images for a better explanation.

Acorns will put out a taproot initially, and as such we should try to use a deep container to accommodate it. I recommend containers that are at least 9″ deep.

But fill your container with moistened potting soil. The soil should be wet enough so that when you squeeze a handful, only a few drops of water fall out. But fill your container up to 1″ below the top, and plant your acorns 1″ deep (2.5 cm). Then, place the container in an unheated garage or shed for the coldest parts of winter.

You can leave the containers outside, as long as they are protected from squirrels, and not at risk of freezing for prolonged periods of time. Acorns must not be allowed to freeze solid, as the acorn will die and no tree will form. I have had this happen to me when I stored pots outside, and they were exposed to very cold temperatures for several days. The entire acorn and soil froze, killing it, and I had little to no germination. If you recall in previous sections, in nature acorns are covered by leaf litter, which provides enough insulation that prevents freezing.

Transplanting Oak seedlings to their final location

In Spring you should begin to see your oak trees sprout up above the dirt. Once they have a pair of leaves developed, you can transplant them to their final location. You will want to select a location where the Oak tree can get sun from all directions to help it grow straight, as well as make sure the soil drains well.

Dig a hole the same depth as the pot, and then poke the bottom with a shovel to loosed the dirt a bit more. Carefully remove the seedling from the pot and place it in the hole. Don’t worry if some of the dirt falls away.

Optional: add a handful of compost to the bottom of the hole.

Protecting young Oak trees from deer and rabbits

Unfortunately for us, young Oak trees are favorite food of deer and rabbits. Deer eat more Oak seedlings than any other animal, and squirrels are also known to dig up young Oak trees. Rabbits will chew the bark of young saplings until they are quite large.

To protect your new tree from deer or rabbits, I strongly recommend using a tree shelter. They usually cost $5-10 with a stake, but will protect the tree for years. I use them on just about everything I plant.

Conclusion

Germinating and growing acorns from seed is a fun Fall activity for kids and adults. Considering many species of Oak will grow upwards of 2′ per year, it is completely possible to reforest an area or plant your own shade trees for almost no money. If you have five years patience, you can have a 10′ tall Red or Pin Oak, which would normally cost hundreds of dollars from a nursery!

It really doesn’t take much effort to do this, simply collect fresh acorns and test them for viability. Then, either sprout or winter sow the acorns and keep them somewhere cool until Spring, when you can safely move them outside to get some sunlight. Within a couple weeks you should have enough true leaves to transplant them to their final location, and at that point just protect them from deer and rabbits.

More native tree articles here