Swiss pine

Swiss pine: how do you recognise it?

Habit

Slow-growing evergreen tree about 15 m tall and 6 m wide; narrow, conical to columnar when young, broader and more irregular with age.

Needles

In bundles of five, 5–12 cm long, fairly stiff; dark green on the outside, striped blue-white on the inside.

Cones

Egg-shaped, 5–8 cm, purplish blue when young, later brown; they do not open by themselves.

Bark

Grey and smooth when young, later grey-brown and fissured.

Roots

A strong root system: move it while young and plant it in its final position.

Plants: April–May and September–October

Why grow it?

• Very hardy, to about −40 °C.
• Slow growth and a narrow shape, about 15 m tall and 6 m wide: a graceful specimen or small group, even in smaller gardens.
• Evergreen, with silvery-green needles in bundles of five.
• No pruning needed and little maintenance.
• The seeds are edible, though in a garden you only get them after many years.

Swiss pine: where does it grow best?

• Full sun: it likes an open, bright spot.
• Fresh, well-drained soil: sand or loam, acid to neutral. No heavy, waterlogged clay.
• Normally moist; no long drought and no wet feet.
• It likes cool summers and grows less well in a hot, dry town corner or against a warm wall.
• Allow 6 m width; with its slow growth it takes many years to get there.

Light

Sun

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal

Size

15 m tall, 6 m wide

Hardiness

Hardy (to -40 °C)

Goes well with

• Dwarf rhododendron: Likes the same fresh, well-drained soil and flowers in spring.
• Heather: Low, colourful planting on acid, well-drained soil.
• Stonecrop: Sturdy and drought tolerant as underplanting in a sunny spot.
• Blue fescue: Blue-grey tufts that match the silvery-green needles.

Swiss pine: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or in September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and just as deep. Loosen the sides so the roots can grow out easily.
3. Set the plant at the same depth as in its pot or root ball: the root collar stays at soil level.
4. Give it 5–6 m from buildings and other trees; in a small group it can stand 3 m apart.
5. Water generously straight away, even if it is raining.
6. Spread a layer of bark or leaf mould mulch around the base, keeping it clear of the trunk.

Care

Water

For the first two years, water generously every week in dry spells. After that only in long droughts.

Feeding

Not needed. On poor sandy soil, give a little compost in spring.

Mulching

Bark or leaf mould keeps the soil cool and moist.

Stake

A young tree in a windy spot gets a stake for two to three years.

Checking

In spring, look for woolly tufts on the twigs and for swollen cankers with orange blisters on branches.

Tip: Plant it in an open spot with well-drained soil and give it time: it often grows only 10–20 cm a year. Do not move it once it is established.

Swiss pine: when to prune it?

When: It does not need pruning: it takes on its narrow shape by itself. Only remove dead, damaged or diseased branches if necessary.

How:

• Cut dead or damaged branches back to the trunk or a side branch.
• Remove a double leader and leave one strong leader.
• Diseased branches (see Problems) are cut back into healthy wood; put them in the household waste, not on the compost heap.

Caution: Never cut into bare wood without needles: a pine will not regrow from it.

Pruning calendar and basic rules

Propagation

Seed

The seeds need a cold period: keep them for a few months in damp sand in the fridge or outdoors in a pot, and sow them in spring. Seedlings grow slowly.

Grafting

Selections, such as compact or extra narrow forms, are grafted by nurseries; seedlings do not come true to the parent plant.

Swiss pine: how does it get through the winter?

Hardy to −40 °C.

• Extremely hardy, to about −40 °C: no protection is needed.
• In a pot: put the pot in a sheltered spot and wrap it in hessian so the roots do not freeze. Water in dry, frost-free weather.

Diseases and pests

• Blister rust: Swollen patches with orange blisters on branches and trunk in spring; the branch dies above them. Cut affected branches back into healthy wood and do not plant currants or gooseberries (Ribes) right next to the pine, as they are the alternate host.
• Woolly aphids: White, woolly tufts on twigs and trunk. Spray them off with a strong jet of water or brush them away with soapy water.
• Needle drop: Old needles turn yellow or brown after a few years and fall in autumn. This is normal; only worry if branches go bare or many needles die on the outside.
• Wet feet: Yellow needles and poor growth in heavy, wet or compacted soil. Choose a well-drained spot.

Through the year

• March: Check for winter damage. Renew the mulch.
• April: Plant. New shoots appear. Watch for blister rust.
• May: Plant. Apply mulch. Water young trees in dry weather.
• June: Water in dry weather. Watch for woolly aphids.
• July: Water young trees in dry weather.
• August: Water in hot, dry weather.
• September: Plant. The cones turn brown.
• October: Plant. Needle drop is normal. Water new plantings.
• November: Move pots to a sheltered spot or wrap them against frost.
• December: Rest. Water pots in dry, frost-free weather.

Did you know?

• In the mountains the nutcracker, a bird, spreads the seeds: it hides them as a winter store, and forgotten seeds germinate.
• Its fragrant wood is used in the Alps for panelling and furniture.
• In the high mountains, old trees can reach several hundred years of age.