Swamp cypress

Swamp cypress: how do you recognise it?

Habit

Deciduous conifer of 20–35 m, narrowly conical at first, broader later; the base of the trunk is often swollen.

Needles

1–2 cm, flat, soft, alternate in two rows on side shoots that fall with them in autumn. Autumn colour coppery brown.

Bark

Red-brown, fibrous.

Cones

Round cones 2–3 cm, almost stalkless.

Knees

Near water, woody, conical outgrowths of the roots stick up out of the ground or the water.

Difference from dawn redwood

In dawn redwood the needles and side shoots are opposite.

Pruning: November–March

Identify by feature: Soft needles · Needles that fall

Looks like it, but isn’t

• Dawn redwood Metasequoia glyptostroboides: needles and side shoots are opposite. Difference from dawn redwood

Why grow it?

• One of the few trees that tolerate wet ground and even shallow water.
• Coppery brown autumn colour and an elegant, bare silhouette in winter.
• Knees by the water: an eye-catcher you rarely see.
• Lives to a great age and suffers little from pests and diseases.

Swamp cypress: where does it grow best?

• Full sun.
• Moist to wet soil, on the edge of a pond or even in shallow water; it also grows in ordinary garden soil, but then without knees.
• Too big for an ordinary garden: allow for 30 m tall and 8 m wide or more.
• Knees only appear near water: plant it by a pond or in a wet corner if you want to see them.

Light

Full sun

Legal basis

Any garden soil

Moisture

Moist to wet

Size

30 m tall, 8 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Dawn redwood: Together by a pond: compare the needles, the autumn colour and the shape.
• Alder: A native tree for the same wet bank.
• Yellow flag: A native waterside plant with yellow flowers in May–June, at the foot between the knees.

Good and bad companions

Goes well with

• Tolerate the shade under this tree: oregon grape, rhododendron, oleaster, japanese skimmia, garden privet, camellia, laurustinus, box-leaved honeysuckle

Swamp cypress: when and how to plant it?

1. Plant from November to March; a pot-grown tree can also go in later in spring.
2. Choose a young tree: it establishes best.
3. Plant on the bank, just above the waterline; later it can stand with its feet in the water.
4. Put a stake on the windward side and tie the trunk loosely; remove stake and tie after 2–3 years.
5. On drier soil, water generously in every dry spell during the first few years.

Care

Watering

Not needed on wet soil; in ordinary garden soil, in dry spells during the first few years.

Feeding

Not needed.

Knees

Mow carefully around them, or let a strip of long grass or waterside plants grow round them.

Autumn

Needles and shoots fall late, in October–November; it’s best to scoop them out of a pond.

Tip: Want to see knees? Plant it on the edge of a pond or where the water table is high: on dry soil it doesn’t form them.

Swamp cypress: when to prune it?

Pruning months: November–March.

When: Dead, diseased and broken branches can be removed at any time of year. If pruning is needed, do it during winter dormancy (November–March).

How:

• Needs little pruning; keep its natural shape.
• On a young tree, remove a double leader in good time, so a single trunk remains.

Caution: Never top it: it would lose its natural shape.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Keep fresh seed cold and moist over winter and sow it in spring in a moist seed tray. Cuttings root poorly: buying a young tree is usually the better option.

Swamp cypress: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• In winter it is bare: that is normal. The needles appear late in spring, sometimes not until May.

Diseases and pests

• Late leafing: In April it is often still bare while other trees are already green. Normal: wait until late May before you think it has died.
• Drought: On dry soil it stays small and the needles turn brown as early as summer. Water young trees, or plant it in a wetter spot.
• Knees in the lawn: Near water they can also pop up in the grass and get in the way of the mower. Mow around them or let a strip of long grass grow.

Through the year

• January: Formative pruning during winter dormancy, if needed.
• February: Prune and plant in mild weather.
• March: Last month for pruning; planting.
• May: The new needles appear late.
• July: Water young trees on drier soil in dry spells.
• October: Coppery brown autumn colour.
• November: Needles and shoots fall; planting and pruning seasons begin.
• December: Remove dead branches; formative pruning possible.

What can you use it for?

Garden and landscape

Ideal by ponds and on wet ground; its root ‘knees’ are an eye-catcher.

Wood

In the southern US known for its very durable, rot-resistant wood.

Did you know?

• The woody knees sticking up out of the water are thought to help the roots breathe.
• In the swamps of North Carolina there are swamp cypresses more than 2000 years old.
• In the southern US it is known for its very durable, rot-resistant wood.
• In the south-eastern USA it forms vast swamp forests; it is the state tree of Louisiana.
• In North Carolina grows a swamp cypress whose growth rings show it to be at least 2,600 years old.