Quercus phellos (Willow Oak)

A handsome and popular shade tree, Quercus phellos, commonly known as Willow Oak, is a deciduous tree admired for its graceful, willow-like leaves. It’s a member of the red oak group and features a straight trunk with a rounded, spreading canopy, offering a blend of elegance and sturdiness that makes it a favorite in both urban and natural settings.

Quercus phellos: An In-depth Look

Native: Willow Oak is native to the south-central and eastern United States, flourishing in the Atlantic Coastal Plain, from New York to Florida and west to Texas and Missouri.

Plant Type and Habit: Long-lived (200 years), Willow Oak is a deciduous tree with a characteristic upright and oval to rounded growth habit. Willow Oak is known for its moderate to rapid growth rate and a form that becomes more impressive with age, featuring a dense, symmetrical canopy ideal for shade and aesthetic appeal.

Size: Willow Oak typically grows 40-60 feet tall (12-18 m) with a spread of about 30-40 feet (9-12 m). Its size, coupled with its open branching structure, makes it an excellent shade tree in a variety of landscapes.

Flowers: The tree produces inconspicuous flowers in spring. Male flowers are yellow-green catkins, while female flowers are smaller and less noticeable. Both male and female flowers are found on the same tree, making it monoecious.

Fruits: The tree bears small, rounded acorns, about 0.5 inches in diameter. These acorns have a thin, saucer-like cap and are striated with brown and black bands.

Foliage: The foliage of Willow Oak is one of its most distinctive features. The leaves, up to 5 inches (12 cm), are slender, lanceolate, and resemble those of a willow, hence the name. They are bright green in spring and summer, turning yellow to russet in the fall before shedding, providing seasonal interest.

Bark: The bark of young Willow Oaks is smooth and light gray. As the tree matures, the bark becomes rougher, developing into a darker gray with ridges and furrows. This textural change adds to the tree’s visual interest, especially in winter.

Hardiness: This oak is hardy in USDA zones 6 through 9. It adapts to a range of soil types, from wet to well-drained, and tolerates urban conditions.

Uses: Willow Oak is extensively used in urban and suburban landscapes for street planting, parks, and large lawns due to its tolerance of pollution and compacted soils. It’s also valued in forested settings for its ecological contributions. The wood is used for timber, furniture, and flooring, though not as extensively as some other oaks.

Wildlife: Oak trees support over 800 caterpillar species in the United States. They are host plants for over 500 species of butterflies, including the Striped Hairstreak, Banded Hairstreak, Edwards Hairstreak, Red Banded Hairstreak, White M Hairstreak, Mourning Cloak, and Horace’s Duskywing. Birds and mammals, including deer and squirrels, consume the acorns.

Deer and Rabbits: While young trees may be susceptible to browsing by deer and rabbits, mature Willow Oaks are less prone to damage. Using protective measures like tree guards can help safeguard saplings from these animals.

Toxicity: The leaves and acorns contain tannic acid, which can be toxic to horses and some pets if ingested in large quantities.

Invasiveness: This species is not considered invasive in its native range.

How to Grow and Care for a Willow Oak Tree

Light: Prefers full sun for optimal growth and health. It can tolerate partial shade but may affect growth rate and foliage density.

Soil: Adapts well to a variety of soil types. Prefers moist, slightly acidic, well-drained soils. Chlorosis due to iron deficiency occurs in high-pH soil. Willow Oak tolerates clay soil and wet soil.

Water: Regular watering is essential, especially for young trees. Mature Willow Oaks have moderate drought tolerance.

Fertilizer: Apply a balanced fertilizer in early spring for young trees. Mature trees typically require less frequent fertilization.

Pruning: Prune in late winter to early spring to remove dead or crossing branches. Maintain a central leader in young trees to promote strong structure.

Propagation: Primarily propagated through seeds (acorns). Best to plant acorns in fall directly in the growing location. Grow your own oak tree: a step-by-step guide to planting acorns. Willow Oak is readily transplanted because of its shallow roots. Transplant in late winter, when dormant. It is also incredibly tolerant of heat, drought, and stress once established.

Pests and Diseases: Potential insects may include scale insects, leafminers, galls, lace bugs, borers, and caterpillars. It can be susceptible to root rot, anthracnose, oak wilt, canker, leaf spot, and powdery mildew. Learn more about the pests and diseases of oak trees. This tree is susceptible to wind damage.