Cork oak.

At a glance

Care level

Moderate

Plant type

Evergreen tree

Light

Full sun

Indoor light

Direct sun

Water

Every 7 to 14 days

Mature size

20 to 30 meters

Growth rate

Slow

Hardiness

USDA 7 to 10

Bloom time

Mid to late spring

Care

Plant this tree in a spot with plenty of sun and well draining soil. Keep an eye out for signs of root rot if the soil stays wet for too long. It is quite drought tolerant once it gets established in your yard.

Watering

Water deeply but infrequently once the tree is established.

Feeding

Apply a balanced fertilizer in early spring to support healthy growth.

Pruning

Remove dead or crossing branches during the dormant winter season.

Repotting

Repot only if the tree is kept in a container and shows signs of being root bound.

Soil

Sandy, acidic, well drained soil

Soil pH

Acidic to neutral

Temperature

-10 to 40°C

Humidity

40 to 70%

Safety

People

The plant is generally non-toxic, but the high tannin content in acorns can cause digestive upset if ingested.

Children

Acorns pose a choking hazard to small children if swallowed.

Contact allergens

The leaves and bark are not known to cause contact dermatitis.

Airborne allergens

The pollen is a significant airborne allergen during the spring flowering season.

Edibility

Acorns are not for human consumption without extensive leaching to remove tannins.

How to identify it

• Thick, deeply fissured corky bark
• Evergreen, leathery, oval shaped leaves
• Small, brown, oval shaped acorns
• Toothed or wavy leaf margins

Height

10 to 20m

Spread

8 to 15m

Leaves

dark green, grayish green, evergreen

Flowers

yellowish green, 0.5 to 1cm

Fruit

brown, Autumn

Common problems

• Phytophthora root rot — A soil-borne pathogen that causes root decay and tree decline.
• Oak borer — Larvae tunnel into the wood, weakening the structural integrity of the trunk.

Growing it

Propagation

seed

When to plant

autumn, spring

Plant drought-tolerant Mediterranean shrubs beneath the canopy to mimic the natural understory of cork oak forests.

Grows well with

• Rockrose — These shrubs thrive in similar dry, Mediterranean conditions.
• Lavender — They share a preference for full sun and well-drained soil.

Similar species

• Holm Oak — It is a closely related evergreen oak with similar environmental requirements.

Science

Family

Fagaceae

Genus

Quercus

Order

Fagales

Class

Magnoliopsida

Native range

Southwest Europe and Northwest Africa.

Conservation

This species is protected in parts of its native range due to the ecological importance of cork oak forests.

It is a fire-adapted species that thrives in Mediterranean climates with dry summers and mild, wet winters.

Value to wildlife

provides shelter, food source for birds and mammals

Pollinators

bees, beetles

Uses

cork production, ornamental shade tree, wildlife habitat

Taxonomy resolved against GBIF.

Questions people ask

How often can you harvest the bark?

The bark is typically harvested every nine to twelve years.

Does it need full sun?

Yes, it thrives best in full sun with well-draining soil.

Where the name comes from

The specific epithet suber is the Latin word for the cork oak itself.

Good to know

• Cork oak trees can live for over two hundred years.
• The bark is fire-resistant, helping the tree survive wildfires.
• Portugal is the world's leading producer of cork from this species.
• The tree does not reach maturity for cork harvesting until it is about twenty-five years old.