Spruce

Picea spp.

1. Identification and origin

Spruces (Picea spp.) are evergreen conifers of the Pinaceae family, native to temperate and cold regions of the Northern Hemisphere, including Europe, Asia and North America. They are widely used in forestry, urban afforestation, timber production and ornamentation. In Portugal, they are mainly planted in gardens, parks and mountain areas.

2. Economic importance

Picea species are of great economic importance in the production of timber, pulp and resin, and are also valued as ornamental and Christmas trees. In forestry, they stand out for the production of lightweight timber and their relatively fast growth. In landscaping, they are appreciated for their conical habit and persistent foliage.

3. Botanical characterisation

Tall evergreen trees, which can reach 20–60 m in height, with a conical crown and whorled branches. The leaves are needle-like, rigid and inserted individually along the branches. The cones are pendent, with woody scales, releasing winged seeds. The root system is shallow, making the tree sensitive to strong winds and compacted soils.

4. Soil and climate requirements

Spruces prefer cold to temperate climates, with high atmospheric humidity. They develop best in deep, cool, well-drained soils, of loamy to sandy-loam texture, with a slightly acidic pH (5.0–6.5). They are sensitive to prolonged droughts, high temperatures and atmospheric pollution. In warmer regions, water stress favours attack by pests and diseases.

5. Main pests

• Pine weevil (Hylobius abietis): damage to the collar and roots of young plants
• Wood-boring beetles (Ips typographus, Pityogenes chalcographus): galleries in the trunk and rapid decline
• Conifer aphids (Cinara spp.): sap sucking and honeydew
• Scale insects (Diaspididae): loss of vigour and yellowing
• Defoliating caterpillars (Dendrolimus pini, Thaumetopoea pityocampa in occasional situations): partial defoliation
• Nematodes (Bursaphelenchus spp.): decline and death in trees infested by the insect vector or through the soil

6. Main diseases

• Resinous canker (Cytospora kunzei): resin exudation and death of branches
• Root rots (Armillaria spp., Heterobasidion annosum): progressive decline
• Rusts (Chrysomyxa spp.): yellow spots and needle drop
• Conifer needle cast (Lophodermium spp.): leaf necrosis
• Collar rots (Phytophthora spp.): wilting and sudden death in waterlogged soils

7. General crop management

The management of spruces includes the choice of species and provenances adapted to the local climate, avoiding plantings in hot or dry areas. Supplementary irrigation is important during periods of water stress. Soil compaction should be avoided and good drainage ensured. Monitoring of wood-boring beetles such as Ips typographus is essential, especially after storms or periods of drought. Pruning should be minimal and carried out only to remove dry or diseased branches.

Bibliographic references

• EPPO Global Database – Picea spp.
• CABI – Crop Protection Compendium – Picea abies
• Wingfield, M. J., et al. (2015). Diseases of conifers. Forest Pathology.
• FAO (2020). Conifer Forest Management Manual.
• Seidl, R., et al. (2017). Bark beetle dynamics in spruce forests. Forest Ecology and Management.
• Hansen, E. M., et al. (2018). Root diseases of conifers. In: Forest Pathology. Springer.