Pin oak

Pin oak: how do you recognise it?

Habit

Tree of 20–25 m with a pyramidal crown: the upper branches grow obliquely upwards, the middle ones horizontally and the lower ones hang down.

Leaf

Alternate, 8–15 cm, glossy, cut almost to the midrib into 5–7 pointed lobes with bristle tips; tufts of brown hairs in the vein axils underneath. Scarlet autumn colour; the dead leaves often hang on for a long time.

Bark

Smooth and greyish-brown for a long time, later finely fissured.

Fruit

Small, almost round acorns (1–1.5 cm) in a shallow cup; they only ripen in their second year.

Difference from red oak

Red oak has larger leaves (12–22 cm) cut only halfway in, and branches that grow obliquely upwards.

Flowering: April–May · Pruning: July–August and November–February

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

Looks like it, but isn’t

• Red oak Quercus rubra: larger leaves (12–22 cm) cut only halfway in; branches grow obliquely upwards. Difference from red oak

Why grow it?

• One of the most fiery autumn colours of all oaks: scarlet to bronze-red.
• Grows faster than our native oaks and tolerates wet soil and occasional flooding.
• A neat, regular crown that is recognisable from afar, even in winter.
• Acorns for jays and squirrels.

Pin oak: where does it grow best?

• Full sun.
• Acid, moist to wet soil; it tolerates occasional flooding. On chalky soil its leaves turn yellow (chlorosis) and it goes into decline.
• On dry sandy soil it grows more slowly and suffers in dry summers.
• Allow for a crown 12 m across and 20 m or more tall: not a tree for an ordinary garden, but for a large garden, a park, an avenue or the edge of a pond.

Light

Full sun

Legal basis

Acid soil

Moisture

Moist to wet

Size

22 m tall, 12 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Swamp cypress: Also likes wet, acid soil and turns russet in autumn: a superb pair beside a pond.
• Sweetgum: Another American tree with fiery autumn colour on moist soil.
• Alder: A native tree for wet soil and banks, whose seeds feed siskins and goldfinches in winter.

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

Pin oak: when and how to plant it?

1. Plant from November to March, in frost-free weather: young trees bare-root, larger ones root-balled.
2. It transplants more easily than most oaks, thanks to its shallow, finely branched root system.
3. Not sure about your soil? Test its acidity: above a pH of about 7, choose a different tree.
4. Put in a stake on the windward side and tie the tree loosely; remove stake and tie after two or three years.
5. Water during dry spells in the first few years.

Care

Watering

During dry spells in the first few years; an established tree on moist soil needs nothing.

Feeding

Not needed. Yellowing caused by chalk can’t be cured with ordinary fertiliser: the soil is simply too chalky.

Mulch

Leave fallen leaves under the tree or spread leaf mould: it keeps the soil moist and acid.

Clearance

The lower branches droop: on an avenue tree or above a path, remove them gradually, a few each year.

Tip: Not sure if your soil is acid enough? Look at what thrives nearby: where rhododendrons, birches and heather do well, the pin oak will feel at home too.

Pin 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 summer or winter.

How:

• Little needed: the crown naturally grows into a regular pyramid. On a young tree, keep a single leader.
• The lower branches droop: on an avenue tree, remove them gradually to create clearance underneath.
• Cut just outside the branch collar and leave no stubs.

Caution: Needs acid soil: on chalk its leaves turn yellow (chlorosis).

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Sow fresh acorns outdoors in autumn, in a deep pot or in open ground; they germinate in spring. Don’t let them dry out, and protect them from mice and jays.

Pin oak: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• The dead leaves often hang on young trees and the lower branches well into winter.
• In winter you can recognise it by its silhouette: drooping lower branches, horizontal middle branches and obliquely rising top branches.

Diseases and pests

• Chlorosis: Yellow leaves with green veins on chalky soil: the tree cannot take up iron there. Only plant it on acid soil; on chalk there is no lasting cure.
• Drought: Brown leaf margins and early leaf fall in dry summers, especially on sandy soil. Water young trees and mulch the soil.
• Drooping branches: Not a disease: the lower branches hang down naturally. Lift the crown gradually if they get in the way.

Through the year

• January: Formative pruning in frost-free weather; the dead leaves are still on the tree.
• February: Finish formative pruning; plant bare-root or root-balled trees.
• May: Leaves emerge: if the young leaves are yellow rather than green, the soil is too chalky.
• July: Summer pruning: gradually remove lower branches; water during dry spells.
• August: Finish summer pruning; water young trees during dry spells.
• October: Scarlet autumn colour; the acorns drop.
• November: Leave the leaves as mulch; plant; winter pruning can start again.
• December: Planting season; formative pruning in frost-free weather.

What can you use it for?

Garden and landscape

Avenue tree with a neat, pyramidal crown and fiery autumn colour.

Wood

Heavy wood for flooring and furniture, less durable than that of our native oaks.

For wildlife

Acorns for jays and squirrels.

Good for wildlife

Birds

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

Did you know?

• A popular street tree: the pyramidal crown with drooping lower branches is recognisable from afar, even in winter.
• It belongs to the red oaks, like red oak itself: their leaf lobes end in bristles and their acorns only ripen in the second year.
• The scientific name palustris means ‘of the marsh’: in North America it grows on ground that is often flooded in winter and spring.
• Palustris means ‘of the marsh’: in the eastern United States it grows naturally on wet, poorly drained ground along rivers.
• It transplants more easily than many other oaks, which is partly why it is one of the most widely planted street and park trees in North America.