Willow Oak Tree (Quercus phellos): Identify Willow Oaks Leaves, Acorns

Willow Oaks are fast growing, medium to large-size deciduous trees under the Red Oak group in the Fagaceae family.⁶

They grow 40 to 80 feet tall and 30 to 60 feet wide. They also have a rounded to oval crown.

They have long lifespans and can reach 120 feet tall. These trees have nice balanced, rounded forms with fine texture making them popular shade trees for the landscape.

Willow Oaks start producing acorns when they reach 15 to 20 years.

They are high value wildlife trees because as an Acorn Tree it feeds small mammals and birds. They are native to the Southeastern United States though they have spread all across North America.

They are typically found in the woods that border canals, streams and swamps.

How Did the Name Quercus phellos Come To Be?

Quercus, the genus name is Latin for oak trees. While phellos is Greek for cork.

These trees usually grow in medium to wet, average, acidic soils. They can survive in both poorly and well-drained soil in light shade or full sun.

Willow Trees adapt well to clay soil and they are tolerant of urban pollution. They have fibrous root systems that transplant well.

They are mostly used as shade trees in large yards, golf courses, parks, commercial establishments, and as street trees. They also do well in water gardens or ponds.

However, these trees are toxic to horses.

How To Identify Willow Oak

Willow Oak Trees are popular choices among landscape architects, homeowners, and urban planners because of their rapid growth, tolerance to a wide range of soil types, and ability to grow in various environments.¹

Since these trees grow quickly, they can be used as screening or windbreaks in large gardens.

Their average lifespan is about 100 years and can reach up to 100 feet. Their best growing conditions are moist soil with plenty of sunlight mostly in the east of the Mississippi river.

Here’s how to identify a Willow Oak.

Willow Oak Leaves

Willow Oak Trees have simple alternate leaves which grow up to 2 to 5 inches long. The Willow Oak leaves are lanceolate or linear in shape.

They look like Willow leaves and have an entire margin.⁷ These leaves also have bristle tips.

Willow Oak Flower and Fruit

Willow Oaks are a monoecious species.

The male part of the Willow Oak flower is born on slender catkins that have a yellow-green coloring. The female comes from very short axillary spikes.

Both parts appear quite early with the leaves.

The Willow Tree produces very small acorns which are about ¼ to ½ inch across. They are yellow-green in color and usually round.

They turn tan when they mature. They have thin, saucer-like caps that cover only 1⁄4 of the acorn. The caps have appressed, tomentose, thin scales.

The Willow Oaks flower and fruit in the summer and fall.

Willow Oak Twigs, Bark, and Form

It’s quite difficult to differentiate Willow Oak twigs, bark, and form from other Oak Trees. The twigs are hairless and slender.

When they are young they are olive-brown in color. They produce multiple terminal buds which are very small, sharp-pointed, and reddish brown.

A medium sized tree grows up to 60 to 80 feet tall. It forms a dense oblong crown if grown in the open.

The lower branches do not self-prune readily. The barks on young stems are tight, gray, and smooth.

As the tree matures they start becoming darker and create irregular rough furrows and ridges.

The Lifespan of a Willow Oak Tree

Willow Oak Trees grow well in poorly drained areas especially in the Gulf Coasts and the Atlantic. They are native to the Mississippi River Valley in North America.

They are widely planted as shade trees or street trees in the southern United States because they can grow quickly and have shallow root systems. You can have a Willow Oak Tree for up to 100 years on average.

They can grow up to 12-24 inches in height in a year.² This growth rate varies across different trees, species and growth zones.

Some Live Oak Trees grow as old as 2,000 years and one such example is the Angel Oak Tree in South Carolina.

In North America alone, you can find nearly 300 different species of Oak Trees. If these trees are cared for, they can provide shelter and food for wild animals for about 100 years.

Willow Oak Disease Prevention

If you plant a Willow Oak, you need to know that it, like other Oak Trees, is susceptible to many pests and diseases. However, these Oak species tend to have good resistance therefore, all you need to do is to properly care for the tree.

Common pests of the Willow Oak may include:

• Oak skeletonizer⁸
• Weevils
• Caterpillars
• Borers
• Lace bugs
• Galls
• Leaf miners

Potential diseases may include:

• Powdery mildew
• Leaf spots
• Cankers
• Chestnut blight
• Oak wilt
• Anthracnose
• Shoestring root rot

Willow Oaks can also get chlorosis that comes from iron deficiency which is a common problem in high pH soil. Wind damage is also a real threat to Oak Trees.

One Willow Oak disease prevention technique is to stop watering a mature Oak every month. While oaks prefer wet soil, they cannot grow well in areas with standing water all through the growing season.

(Image: F. D. Richards¹¹)

You should prevent drying out of the soil surrounding the tree by covering it with mulch at the tree base.

• Leaf spots: The most common signs of leaf spot disease are spotty holes on the surface, dead areas on leaf margins, and leaves turning brown. Proper drainage, mulching and watering will help prevent this disease.
• Shoestring root rot: Signs of these diseases are yellow and stunted leaves, and fuzzy white fungus between the tree and the bark. You will have to call an arborist if you see these signs.
  The disease can be stopped in its infancy with correct tools and techniques. However, if a tree is severely affected it will have to be removed.
• Powdery mildew: Signs of powdery mildew include gray white patches that normally appear on top of the leaves. Sometimes these patches appear on fruits, blossoms, buds, stems and underside of the leaves.
  You can prevent powdery mildew by trimming infected leaves and crowded areas.

Besides the diseases listed above, oaks may also get chestnut blight, oak wilt, and other blisters and cankers. To prevent these issues you need to maintain a healthy tree by checking on it and pruning regularly.

Willow Oak Growing Zone: When To Plant Willow Oak for the Best Yield

The Quercus phellos is native to the United States.

Growing zones for Willow Oak, where to grow are the USDA zones 5 or 6a through 9b. This means that the range of the Willow Oak growing zone includes:

• The entire south and south west
• Most of the east coast and
• The entire west coast of the country

If you want to know when to plant Willow Oak for the best yield, you should understand the climate, soil and topography, and the reproduction and growth of the tree.

Climate

Willow oaks grow in temperate and humid climates characterized by short mild winters and long hot summers.³ They grow in zones where daily temperatures are above 32° F (0°C).

In the north-northeastern range, the frost free days should be about 185 and in the south-southwestern range they should be about 300.

The average temperature in the summer should be around 75° F or 25°C and in the winter they should be about 25° F or 2°C. However, they can survive in extreme winter temperatures of up to -20° F.

The Willow Oak Tree needs about 2,700 hours of sunshine annually.

Soils and Topography

Willow Oaks grow best in alluvial soils commonly found in ridges or close to major streams. They grow best on new alluvium or clay loam ridges.

Willow Oak quality increases from lower to the higher topographic position within a floodplain. Additionally, growth rate and quality are affected by available moisture and the characteristics of the soil.

(Image: Katja Schulz¹⁰)

The best soils to grow Willow Oaks should be deep around 4 feet, relatively undisturbed and without pan. These soils should be loam or silty, medium textured, and 12 feet without compaction.

They should also be granular in the rooting zone. The soil must have available moisture during the growing season for best growth.

Lastly the topsoil should be 6-inch-deep with two percent organic matter. The pH of the soil should range between 4.5 and 5.5.

Willow Oak Seeds Production and Dissemination

The trees start to produce seeds when they are 15 to 20 years old. They produce small acorns that are about 2 to 4 inches wide.

These acorns occur solitary or in pairs. The acorns mature in the fall, between August and October in the second year after flowering.

Usually, the acorns that fall first are not mature. This is indicated by the cup failing to detach easily.

Mature acorns are brightly colored, heavy, and have a brown micropylar end.

These trees produce a good seed crop every year. Mature Willow Oaks produce about 11 to 69 pounds of acorns annually.

Each tree can produce about 5,440 to 32,000 seeds each year. These seeds are disseminated by animals as they feed on the acorns.

You can store the acorns under moist cold conditions.

Growing Willow Oak from a seed is a simple process. For germination to occur, the moisture content should be above 40%, preferably 50%.

The seeds should be stored for 60 to 90 days at about 35° F before planting.⁴

Vegetative Reproduction

Like other trees, Willow Oaks can sprout from stumps of small trees through the process of natural regeneration. Stumps with large diameters do not sprout as easily.

Growing Willow Oak from a cutting involves propagating.

You can take cuttings from young parent trees and propagate them by treating them with indole acetic acid. The age of the parent tree determines the success of this process as it decreases with age.

Budding and layering will not be effective as a means of vegetative reproduction.

Growing Willow Oak From a Seedling

Do you know that growing Willow Oak from a seedling is quite easy. All you have to do is germinate the seed.

Like all oaks, these trees produce loads of seeds. You can harvest ripe acorns from late October to early November.

In general, you will get mature willow oak seeds one year after they are produced.

When you start collecting your acorns, experts recommend choosing ripe ones that have turned brown as opposed to green acorns which have not yet matured. Then you should soak the acorns for 24 hours and discard any that float on water as they have been damaged by insects.

You can plant the acorns on containers and let them germinate to form seedlings.

If you want improved germination, you should put the seeds in cold stratification for two to three months. For this reason, you should consider planting more than needed to get some seedlings to share with friends and family.

When planting, remove the caps of the acorns and plant the bottom part 12 inches in the soil.

You should thin your seedlings after the second year. Water them constantly though not during the winter.

Spread a thin layer of mulch on the seeds and overall you will have a rewarding harvest.

Special Uses of the Willow Oak Tree

These trees produce acorn crops every year, therefore, they are important for wildlife food production. The trees supply food to game animals such as:

• Ducks
• Turkey
• Deer
• Squirrels
• Woodpeckers
• Blue jays

They also provide homes to birds, squirrels, mice, flickers, and grackles.

They are among the favored shade trees and are sometimes planted for ornamental purposes. They are great species to plant along margins of reservoirs with fluctuating levels.

Additionally, these trees can be harvested when they are young and used as biomass. Lastly, they are used in hardwood plantations as they provide a good combination of fast growth rate and excellent pulping characteristics.

Companion Plants for Growing Willow Oak

If you want to know a companion plant for growing Willow Oak, the most recommended are plants that can grow in a shade. Native plants grow well in close proximity to Willow Oak Trees.

Low maintenance evergreen shrubs can grow well with these trees.

(Image: Dyzio88¹³)

Any shade loving plant whether foreign or native is suitable to grow under a Willow Tree. Such plants include:

• White Trillium⁹
• Daffodils
• Carpet Bugle
• Solomon’s Seal
• Jack in the Pulpit
• Lilies of the Valley
• Hostas
• Vinca minor

Willow Oak vs Pin Oak

The Willow Oak Tree is about 60 to 100 feet tall and has a trunk diameter of about 3-5 feet. It grows rapidly with a growth rate of about 2 feet annually.

The Pin Oak grows about 50 to 75 feet tall and has a tree trunk diameter of about 2-4 feet. It’s safe to infer that Pin Oaks are slightly smaller than Willow Oaks.⁵

(Image: Dan Keck¹²)

The main difference however is in the leaves.

Willow Oak leaves are long and thin. They have smooth leaf edges and the leaf color and position alternates according to season.

In the autumn the leaves turn orange or red and fall from the tree. Among the types of Willow Trees, you will find that they have similar leaves to Willow Oak Trees.

The leaves of the Pin Oak turn deep bronze in autumn. They have longer, broader leaves about 6 inches long and 4 inches wide.

The barks of Willow and Pin Oak trees also have distinctive differences. The Willow Oak has a brownish bark.

Young trees have smooth light gray barks that later turn dark brown. Old trees have a lot of cracks on their barks.

When Pin Oaks are young, they have smooth and light green barks. Over time, these barks turn dark gray and become rougher and more loose, spreading canopy.

They are among types of Oak Trees in California.

The Willow Oak Tree is under the Red Oak group and its willow-shaped leaves are its distinguishing features including beautiful winter features, attractive bark, rounded form and excellent texture which makes it a great ornamental tree.

Frequently Asked Questions About Willow Oak