Siberian spruce

How to recognise it

Habit

Straight, slender tree with a narrow, pointed crown; 20–35 m tall in the wild, usually less here. Branches level to slightly drooping. The grey-brown bark later flakes off in thin plates.

Needles

Four-sided, stiff and short, 1–2 cm, dull dark green to greyish green. They grow all round the shoot on small woody pegs, which leave the shoot rough once the needles fall.

Cones

Hanging, egg-shaped to shortly cylindrical, 5–8 cm long. Green or purple when young, ripe and brown in the autumn of the same year. The scales are broadly rounded with a smooth, entire edge.

Shoots

Young shoots are yellowish brown to reddish brown and densely covered in fine hairs; the buds are small and egg-shaped.

Roots

A shallow, flat root system: sensitive to drought and, on wet ground, liable to blow over.

Confusion with

Norway spruce: longer cones, 10–15 cm, with pointed or wavy-toothed scale tips, and usually hairless or sparsely hairy shoots. Where both grow together there are many intermediates. Serbian spruce: flat needles with two white bands underneath and a very narrow crown.

Flowering: May–June · Pruning: August–September

Why grow it?

• One of the hardiest trees in the world: it grows up to the northern tree line in Siberia, where winter temperatures fall below −40 °C.
• A dense evergreen crown that gives birds cover, roosts and nest sites all year; goldcrests and tits search the needles for insects.
• The seeds in the cones feed crossbills, siskins and the great spotted woodpecker, which wedges the cones in a crack to hack them open.
• A narrow, regular cone shape that gives structure to a large garden or park, even in winter.
• Fascinating for tree lovers: next to a Norway spruce you immediately see the differences in cones and shoots between two closely related species.

Siberian spruce: where does it grow best?

• In the wild: vast coniferous forests of the taiga, often on moist ground along rivers and in valleys, with birch, larch, pine and fir.
• Sun to partial shade; young trees tolerate quite a lot of shade.
• Cool, moisture-retentive, preferably slightly acid soil: sand, loam or peaty ground. It copes poorly with hot, dry summers and dry chalky soil.
• In the garden: only for a large garden or park, as a specimen or in a group, at least 6–8 m from houses and other large trees.

Goes well with

• Silver birch: A light, white trunk next to the dark green, just as in the taiga.
• European larch: A conifer that turns golden yellow in autumn and stands bare in winter.
• Rowan: White flowers in May and red berries for birds at the edge of the crown.
• Bilberry: Low ground cover on acid, humus-rich soil.
• Narrow buckler-fern: Green underplanting in the partial shade beneath the branches.

Siberian spruce: when and how to plant it?

1. Buy a young tree from a specialist tree nursery or a nursery for unusual conifers. Never take seedlings or young trees from the wild.
2. Plant in October–November or in March–April, when the ground is not frozen. Small trees of 60–100 cm establish best.
3. Dig a wide but shallow planting hole, loosen the bottom and set the root ball at the same depth as it was in the pot.
4. Drive a short stake in at an angle on the windward side and tie the tree loosely; remove the stake after two years.
5. Water in thoroughly straight away and spread a layer of needle litter, bark or leaf mould around the base.
6. Water during dry spells for the first two summers: the shallow roots dry out quickly.

Care

Water

For the first two years, once a week in dry weather, a good soaking each time. After that only in long, hot droughts.

Feeding

Not needed. Leave fallen needles where they lie: they form a natural litter layer that keeps the soil slightly acid.

Mulching

A layer of wood chips or needle litter keeps the roots cool and moist in summer.

Lower branches

Leave them: the tree looks best when branched right down to the ground, and birds like to shelter there.

Late frost

In our mild climate it can come into leaf early. Avoid hollows where cold air collects; on young trees, cover the shoots with fleece on frosty nights.

Tip: Plant Siberian spruce in an open, slightly raised spot rather than in a cold hollow: there it suffers far less from late frost on its young shoots.

Pruning and mowing

Pruning months: August–September.

When: Rarely needed. Remove dead or damaged branches in August–September.

How:

• Saw off dead, broken or diseased branches close to the trunk, just outside the swollen branch collar.
• If a young tree has two leaders, keep the strongest and cut out the other.
• Never cut back into bare wood without needles: a spruce will not regrow from there.
• Only remove lower branches if you really must, for example for a path.

Caution: Never top a spruce: it will form several leaders and lose its fine conical shape for good.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Pick cones in September–October, let them open in a warm, dry place and store the seed cool and dry. Sow in March–April in a seed tray; a few weeks cold and moist in the fridge (stratification) improves germination. Shade the seedlings from strong sun.

Grafting

Special forms are grafted by nurseries onto a Norway spruce rootstock. That is a job for the specialist.

Siberian spruce: how does it get through the winter?

Hardy to −45 °C.

• Evergreen and extremely hardy: a Belgian winter is a mild one for this tree.
• The cones hang on the tree for a long time and provide seed for crossbills, siskins and woodpeckers.
• The dense crown is a sheltered roost for small birds on cold nights.
• After a mild winter it can start growing too early; a late frost then scorches the young shoots, but the tree usually recovers.

Diseases and pests

• Green spruce aphid: A small green aphid that feeds on older needles in winter and spring; they turn yellow and drop, especially after a mild winter. The tree usually recovers on its own, and tits eat the aphids.
• Red spider mite: Tiny mites make the needles dull and greyish in hot, dry summers. Watering and a not-too-hot, airy spot help.
• Spruce bark beetle: This bark beetle mainly attacks weakened spruces after dry summers. A healthy tree in a cool spot is the best protection; remove badly affected trees in good time.
• Drought: Brown needles and dead branches after a hot summer. Mulching and watering help; on dry sandy soil it is not a good choice.
• Windthrow: Because of its shallow roots it can blow over in a storm on wet ground. Avoid spots where water stands.

Through the year

• January: Dormant. Withstands any Belgian winter.
• March: Planting possible as long as the ground is not frozen.
• April: Planting. The buds swell; in a mild spring it sometimes starts growing early.
• May: Flowering: yellow male and green to purple female cones. Fresh light-green shoots.
• June: End of flowering. Water young trees in dry weather.
• July: Water in heat and drought. Watch out for red spider mite.
• August: Saw off dead or broken branches.
• September: Cones ripen. Last month for pruning work.
• October: Pick cones for seed. Good month for planting.
• November: Planting. Crossbills and siskins look for seed in the crown.
• December: Evergreen outline; birds shelter in the dense crown.

Did you know?

• The name obovata means ‘reverse egg-shaped’ and refers to the cone scales, which are broadly rounded at the top.
• Where Siberian spruce and Norway spruce meet, from Finland to the Urals, they hybridise freely and form a broad zone of intermediate trees.
• It grows right up to the northern tree line, where summer lasts only a few weeks and the ground freezes deep down.