How to Grow and Care for a Red Oak Tree

Red oaks (Quercus rubra) are stately trees with fantastic shade and fall foliage. These magnificent trees, native to the east coast of North America, grow to be large trees averaging 75 feet tall and about 40 to 60 feet wide. This tree will require a lot of space and will likely live anywhere from 150 to 500 years.

Red oaks are great trees to plant if you live in the American Northeast. Besides being aesthetically pleasing and a superb shade tree, the red oak is invaluable ecologically. This tree hosts several dozen pollinators, including Juvenal's duskywing, banded hairstreak, Clymene moth, imperial moth, and the rosy maple moth.

Red Oak Care

Red oak won't require much care once it becomes established other than some light preventive maintenance and watching out for rare insect or disease problems. It is a carefree tree as long as it stays healthy and is given a good start.

You can start it from a sapling (the quicker and easier route) or propagate your own. Wherever you decide to plant it, give it plenty of growing space. Ideally, give it a sunny spot where soil drains well and water it once a week.

Light

Place your red oak in a place that will receive plenty of sunlight. Oaks need full sun to part sun to thrive; giving anything less will cause some issues. Even if you plant it near another tree, it will like some room to allow its canopy to get sunlight.

Soil

Though not incredibly picky about its soil, if you want your oak at its happiest, you will want to give it sandy, well-draining soil that is somewhat rich and acidic. Test your soil's pH before planting to check if you need to adjust the pH.

Never layer more than an inch of soil over its roots. All roots need room, but this is especially important for oaks.

Water

While your oak establishes its roots and matures for the first few years, you should water it weekly. It will take a good amount of water, especially during dry periods; 10 gallons per inch of trunk diameter is a good standard. Once your oak is established, don't worry about watering it any further; Mother Nature should take care of it just fine.

Temperature and Humidity

Red oaks are frost-resistant and handle the cold, wet winters and hot, humid summers of the Northeast and Mid-Atlantic. As the climate changes and warms, their zones are shifting northward. They are presently listed as USDA Zone 4-8.

Fertilizer

Your oak should not need any supplemental fertilizer. In the rare case that your oak seems lagging, you should test the soil and check for soil deficiencies. To correct any nutrient deficiencies, fertilize with the appropriate NPK formulation to compensate for the deficient nutrient with a slow-release fertilizer at the tree's drip line.

Types of Red Oak Trees

Northern red oak (Quercus rubra) and Southern red oak (Quercus falcata) are different species. Both are oaks, make acorns, and overlap in growing ranges, but the shape of their leaves, bark type, overall size, and acorn sizes differ.

Primarily, northern red oaks are larger trees and can withstand colder climates. Southern oaks have a more extensive distribution across the American South.

Here are a few other less common red oak trees:

• Willow oak (Quercus phellos): Grows along the Atlantic, Gulf Plains, and Mississippi Valley; distributed across the South, growing as a shade or street tree; can live over 100 years and grow over 100 feet tall; has willow-shaped leaves
• Southern live oak (Quercus virginiana): Grows in Cuba and the Atlantic and Gulf states; has distinctive, sturdy meandering branches; up to 50 feet tall, needs well-drained soil; can grow up to 300 years old
• Black oak (Quercus velutina): Distinctive dark blackish or brownish-gray bark; grows in the eastern United States; does not tolerate shade or growing on slopes
• Pin Oak (Quercus palustris): Also called Swamp Spanish oak; grows in Central and Eastern United States; pyramid-shaped crown and hanging branches at its base; grows about 50 to 70 feet tall
  

Pruning

Prune in the dormant season to avoid the spread of oak wilt disease. Remove dead, diseased, or damaged branches using sterilized pruning tools. You can identify dead branches as feeling brittle. Diseased and damaged branches have blemishes, wounds, discoloration, or scars.

You can prune away up to 1/3 of old wood in a season. Sterilize your tools in between cuts. Remove limbs that crisscross other limbs and cut off shoots that grow vertically straight or downward. Clip off branches that grow at less than a 30-degree angle to the tree trunk. Remove old and weak wood to provide air circulation and light, helping the tree fight disease and pest infestations.

Growing a Red Oak From an Acorn

This method can be used for any tree in the genus Quercus, but be warned the genus is slow to germinate.

When you're ready to select your acorn, only collect the second acorn batch that drops that season. Some years the acorns will be plentiful; this is called a mast year. Unfortunately, you may not get many in other years and may need to hunt for them. It would help if you collected enough to have extra in case some acorns don't germinate.

Next, gently remove the caps of the acorns; these are protective covers of the seed material. Unless you tear into the seed, you will not be damaging the seed by removing the cap. Once all the caps are removed, you will want to perform a float test. Place your acorns in a large container of water and set them aside for five minutes or so. If any acorns are floating, these are not viable seed material.

The next essential step is stratification. You want to thoroughly dry your acorns and place them in a plastic bag filled with damp vermiculite, perlite, peat, or sawdust, and seal the bag. Place the sealed bag in your refrigerator for 45 to 60 days, and you will want to look for germination after 45 days or so.

Your seedling is now ready to be transplanted into a small pot filled with good-quality potting soil and allowed to grow until it is 12 to 18 inches tall. At that point, it is ready to be transplanted to its place in your yard.

Planting a Red Oak Tree

Whether planting a seedling you have grown from an acorn or transplanting a sapling, you must locate a spot that can accommodate a future tree up to 100 feet tall and 60 feet wide. Remove all grass within a three-foot diameter from the tree, so it doesn't compete with the tree for water.

Dig a planting hole twice as wide and deep as the seedling pot (or rootball). It should have a long tap root that goes straight down. Dig a hole deep enough to put the whole tap root in without bending it. Carefully remove the roots and set them in the hole with the root collar (where the stem meets the root system) at ground level.

Check that the tree is plumb, then backfill the hole with compost-enriched soil; firmly tamp but do not mound the soil up against the stem/trunk. Water thoroughly. Water twice a week for the first year and once a week in the second year. Afterward, unless it's unseasonably dry, no supplemental water is needed.

Mulch over the entire rooting area with 2 to 4 inches of bark mulch. Keep the mulch at least three inches from the stem/trunk. Do not use amendments or fertilizer in the first year.

Overwintering

Oak trees can withstand cold winter weather and don't need winter protection. However, a newly planted sapling would benefit from a winter wrap in its first three years to prevent it from getting sunscalded and save it from harsh cold winds.

If you are growing a young oak outdoors in a container in a freezing cold climate, the continuous freezing and thawing cycles, particularly in containers, can be challenging for new trees. Trees freeze and enter dormancy; however, on unseasonably warmer or sunnier days, the container may warm up, spur the plant out of dormancy, then kill the plant in the next freeze.

You can save your tree by moving it to an unheated garage or shed. Before you move it, keep it well-watered and allow it to endure a few frost periods outside, ensuring it enters dormancy. Once dormant, move the container inside to an unheated garage or shed. Do not let the plant dry out; water it sparingly, keeping the soil slightly moist. Move the tree back outside after the last frost.

Common Pests & Plant Diseases

Oaks are susceptible to oak leaf blister, a fungal infection that can look like water blisters on the leaves. It can cause a midsummer leaf drop. If you otherwise keep the tree healthy and on a regular water schedule, it should be able to fight the infection independently. For a young tree, you can give it a fungicide treatment to help fight the fungus.

Bacterial leaf scorch is another common occurrence among red oak trees. Summer droughts are often the cause. It affects water uptake, eventually leading to decline, leaf yellowing and browning, leaf drop, dieback, and death. Insects spread this bacteria. It's best to remove the infected tree to prevent the spread of the deadly bacteria.

Like all trees, this tree can get fungus cankers, which look like white and brown growths on the tree's bark. Remove the branches that develop these growths when you notice them using sterilized pruning tools.

Oak wilt is a certain death sentence; this fungus is currently found in Kansas, Nebraska, and South Dakota.

Common pests that like these trees are leafhoppers or caterpillars. Birds will feed on those insects to control them.

Common Problems With Red Oak Trees

This relatively easy-care tree has few major problems, except those specific to oak trees.

Browning of Top Leaves

Oak wilt is a severe fungal disease causing the browning of the tree's crown, eventually leading to other parts of the tree, then certain death. Beetles spread the disease, usually spreading the fungus in the tree's vascular system through open cuts or wounds (usually from pruning). Recovery is not possible; removal is recommended. This fungus currently exists in Kansas, Nebraska, and South Dakota.

Pale or Unseasonal Yellowing of Leaves

Northern red oaks are susceptible to chlorosis, which causes deep green leaves to become pale or yellow. This condition is often caused when the soil pH is 7 to 7.5. This can be easily corrected by injecting iron into the trunk or treating the soil with sulfur.

Powdery White Leaves

Leaves with a powdery white appearance likely have powdery mildew, a fungal infection. Leaves may also look malformed, drop, or shrivel up. Treat young trees with a fungicide at least 24 hours before rain or watering. Mature trees do not need treatment.