English oak

English oak: how do you recognise it?

Habit

Large tree of 25–40 m with a broad, irregular crown and thick, twisting branches; when free-standing often wider than tall.

Leaf

Alternate, 7–14 cm, with 4–7 pairs of rounded lobes. Leaf stalk very short (under 1 cm); the leaf base has two small ears.

Bark

Grey, deeply and coarsely furrowed.

Flower

Hanging yellow-green catkins (male) and inconspicuous female flowers, in April–May with the young leaves.

Fruit

Acorns in groups of 1–3 on a long stalk (3–8 cm), ripe in September–October.

Difference from sessile oak

Sessile oak has a leaf stalk of 1–2.5 cm, a wedge-shaped leaf base without ears and stalkless acorns.

Flowering: April–May · Harvest and fruit: May–June and September–October · Pruning: July–August and November–February

Identify by feature: Lobed leaves (like an oak) · Nuts, acorns and chestnuts

Looks like it, but isn’t

• Sessile oak Quercus petraea: leaf stalk 1–2.5 cm, wedge-shaped leaf base without ear lobes, and stalkless acorns. Difference from sessile oak

Why grow it?

• The richest tree for wildlife: hundreds of species of insects, fungi, birds and bats depend on it.
• A tree for generations: it lives for hundreds of years and grows more beautiful every year.
• In autumn its acorns feed jays, squirrels, woodpeckers and mice.
• Grows on almost any soil, even heavy, damp clay.
• Little pruning needed: an oak grows best when left alone.

English oak: where does it grow best?

• Full sun: it grows poorly in the shade of other trees.
• Almost any soil, from sand to heavy clay; it also tolerates damp ground and a temporarily high water table.
• Deep roots: plant it at least 15 m from buildings, drains and pipes.
• Allow for a crown 20 m wide or more: only for a large garden, a meadow or a line of trees.

Light

Full sun

Legal basis

Any garden soil

Moisture

Normal

Size

35 m tall, 20 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Hazel: A native shrub that likes the light shade at the edge of an oak.
• Hawthorn: Together a rich edge of blossom, berries and nesting places for birds.
• Common honeysuckle: Climbs into the lower branches and is fragrant in the evening for moths.
• Wood anemone: Flowers in spring under the still-bare crown.

Good and bad companions

Goes well with

• Like the acid soil under this tree: heather, rhododendron, japanese skimmia, raspberry, highbush blueberry, witch hazel, broom, gorse
• Tolerate the shade under this tree: oregon grape, rhododendron, oleaster, japanese skimmia, garden privet, camellia, laurustinus, box-leaved honeysuckle

English oak: when and how to plant it?

1. Plant from November to March when the ground isn’t frozen; young, small bare-root trees of 60–120 cm establish best.
2. Dig a hole deep enough for the taproot without bending it.
3. Put a stake on the windward side and tie the trunk loosely; remove stake and tie after 2–3 years.
4. Protect the trunk from rabbits and deer with a guard or tree shelter.
5. Water generously after planting and during dry spells in the first year.

Care

Watering

In dry spells during the first and second year; after that its deep roots cope.

Feeding

Not needed. Leave the fallen leaves under the tree: they turn into humus.

Under the tree

Don’t mow or dig right up to the trunk; leave a strip of long grass or leaf litter for the roots and soil life.

Old trees

Leave dead wood where it is safe: it is valuable for beetles, woodpeckers and fungi.

Oak processionary moth

From May to July, check for nests on the trunk or thick branches, especially near a play area or patio.

Tip: Plant a young, small oak rather than a large one: it establishes better and catches up with a big tree within a few years.

English oak: when to prune it?

Pruning months: July–August and November–February.

When: Dead, diseased and broken branches can be removed at any time of year. Formative pruning in winter or summer, not during leaf-out in spring.

How:

• An oak grows best when left alone: prune as little as possible.
• Train a young tree on a single leader; gradually remove competing leaders and branches that hang too low.
• Cut large branches in three steps, just outside the branch collar.
• Keep old trees with dead wood where it is safe: it is valuable for wildlife.

Caution: Spotted nests of the oak processionary caterpillar? Don’t prune yourself; have them removed professionally.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

In October, gather fresh, heavy acorns without holes and sow them straight away, 3–5 cm deep, in a pot or where they are to grow. Don’t let them dry out, or they won’t germinate.

Moving a seedling

A self-sown seedling can be moved in its first or second year; later the taproot is too long.

English oak: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy, even in severe winters.
• In winter, protect young trees from rabbits and deer with a guard or shelter.

Diseases and pests

• Oak processionary moth: Caterpillars in groups with irritating hairs, in nests on the trunk (May–July). Don’t touch them; have the nests removed by a professional. Tits eat the caterpillars: put up nest boxes.
• Oak powdery mildew: White fungal coating on young leaves, especially on the second flush in summer. Harmless to an old tree; it slightly slows young oaks.
• Gall wasps: Balls or growths on leaves and twigs (oak apples, marble galls). Harmless: leave them.
• Honey fungus: Honey-coloured toadstools at the base and white fungal sheets under the bark: root rot. Have an arborist check the tree’s stability.

Through the year

• January: Remove dead and broken branches. Plant bare-root trees in mild weather.
• February: Last month for planting and for winter formative pruning.
• March: Planting season ends; water young trees in dry spells.
• April: Leaves and flowers (catkins) open: don’t prune.
• May: Watch for oak processionary moth nests.
• June: Second flush (Lammas growth); check young trees for mildew.
• July: Summer pruning of young trees; keep watching for processionary caterpillars.
• August: Summer pruning still possible; water young trees in dry spells.
• September: The first acorns fall.
• October: Gather acorns for sowing; autumn colour.
• November: Planting season starts; winter formative pruning possible.
• December: Remove dead branches; protect young trees from browsing.

What can you use it for?

Wood

Heavy, durable wood for beams, flooring, furniture, wine barrels and, in the past, ships.

For wildlife

The richest tree for wildlife in our region: hundreds of species of insects, fungi and birds depend on it.

Also used for

The bark provided tannin for leather; acorns were fed to pigs.

Caution: In summer the oak processionary caterpillar can spread irritating hairs: avoid contact with the nests.

Edible and useful

Nuts (September–October)

Gather acorns in September and October. Raw, they are bitter and hard to digest because of their tannins; once thoroughly leached in water they become a nourishing ingredient for flour, porridge or a coffee substitute. Keep only sound, heavy acorns without holes; any that float in a bucket of water go on the compost.

Leaves (May–June)

Young, soft leaves in May and June, for oak-leaf wine, an old aperitif from the south of France.

Storing

Dry acorns for a few weeks in an open crate somewhere airy; in their shells they then keep for months. Leached, thoroughly dried meal keeps for a few months in a closed jar in a cool, dark place, or longer in the freezer.

Caution: Never eat acorns raw or insufficiently leached: the tannins cause stomach upset and an astringent taste. Do not confuse them with conkers (horse chestnuts), which are poisonous. From May to August the oak processionary caterpillar may be in the tree: keep away from the nests and do not pick or gather anything under a tree that has them, as the stinging hairs stay active for a long time. Pick well away from busy roads and sprayed fields, and never eat anything you have not identified with certainty.

Eating and using is at your own risk: see the terms of use.

Recipes

• Leached acorn flour (Dried · ± 300 g flour · 1 hr + 3–7 days leaching + drying)
• Acorn coffee (Other · ± 150 g · 1 hr 15 + leaching)
• Oak-leaf wine (Liqueur · ± 1.2 litres · 15 min + 6 weeks steeping + 1 month resting)
• Acorn flour biscuits (Dish · ± 24 biscuits · 30 min + 30 min resting)
• Fermented gherkins with oak leaves (Fermentation · ± 1 jar of 1.5 litres · 30 min + 5–10 days fermenting)

Good for wildlife

Caterpillars

Host plant: caterpillars of butterflies or moths eat the leaves.

Birds

Berries, seeds or insects as food, or a place to nest.

Bats

Attracts insects in the evening that bats hunt.

Hedgehogs

Shelter and a layer of leaf litter full of insects.

Did you know?

• An old oak is home to hundreds of species of insects, fungi and birds.
• At the end of June an oak often puts out a second flush of leaves, known as Lammas growth.
• Every autumn jays hide thousands of acorns and don’t find them all again: that is how they plant new oaks.
• Oak galls, the little balls that gall wasps cause on oaks, were used for centuries to make iron gall ink: the ink of medieval manuscripts.
• In autumn a jay hides thousands of acorns as winter stores. The acorns it forgets grow into new oaks.