Softwood Timber Species: The Science Behind Their Performance in Landscaping and Construction

At first glance, two pieces of softwood timber may appear almost identical. They might share similar dimensions, moisture content and treatment levels, yet perform very differently once installed.

The reason lies within the wood itself.

Every timber species has evolved to survive in different climates and conditions. These environmental pressures influence cellular structure, growth rate, density, resin content and fibre arrangement, all of which directly affect how the timber performs in landscaping and construction applications.

Understanding these technical characteristics allows specifiers, contractors and homeowners to select the most suitable material for the intended application, rather than relying solely on price.

Understanding Softwood Anatomy

Before comparing species, it is important to understand what makes one timber perform differently from another.

Softwoods are primarily composed of elongated cells called tracheids.

Unlike hardwoods, which contain vessels and pores, softwoods rely on these tracheids for both:

• Water transport
• Structural support

Typically, around 90-95% of a softwood’s cellular structure consists of tracheids.

The characteristics of these cells largely determine:

• Strength
• Density
• Machinability
• Treatment uptake
• Dimensional stability

Several anatomical features are particularly important.

Growth Ring Width

Slow-growing trees produce tighter annual growth rings.

This results in:

• Higher density
• Increased strength
• Greater dimensional stability
• Better wear resistance

Fast-growing timber generally exhibits:

• Wider growth rings
• Lower density
• Reduced strength
• Greater movement

This is one reason Scandinavian timber is often superior to rapidly grown plantation timber.

Latewood and Earlywood

Each annual growth ring consists of two sections.

Earlywood (Spring Growth)

Produced when growth is rapid.

Characteristics:

• Large cells
• Thin cell walls
• Lower density
• Softer material

Latewood (Summer Growth)

Produced when growth slows.

Characteristics:

• Smaller cells
• Thick cell walls
• Greater density
• Increased strength

Species containing a higher proportion of latewood typically display:

• Better structural performance
• Improved wear resistance
• Cleaner machining quality

Resin Canals

Certain species contain resin canals.

These natural pathways carry resins and extractives through the tree.

Benefits include:

• Enhanced natural durability
• Improved fungal resistance
• Water repellency

Species with significant resin content include:

• Scots Pine (Redwood)
• Douglas Fir
• Larch

Scandinavian Redwood (Pinus sylvestris)

Species Overview

Scandinavian Redwood is derived predominantly from slow-grown Scots Pine harvested from northern Europe.

The combination of cold winters, short growing seasons and poor soils forces trees to grow slowly.

This generally produces:

• Narrow annual rings
• Higher latewood percentages
• Increased density
• Superior structural characteristics

This is why Scandinavian Redwood occupies the premium end of the softwood market.

Cellular Structure

Scots Pine possesses relatively large permeable sapwood zones surrounding a denser heartwood core.

The sapwood contains open pathways which allow preservatives to penetrate deeply during pressure treatment.

This characteristic makes Redwood one of the most treatable commercial softwoods available.

In practical terms this means:

• Better preservative retention
• Improved protection against fungal attack
• Longer expected service life

This explains why Redwood is heavily favoured for:

• Decking
• Pergolas
• Garden structures
• Sleepers
• Exterior joinery

Density and Mechanical Performance

Typical density:

470 to 550 kg/m³

Typical bending strength:

70-100 N/mm²

Modulus of Elasticity:

9,500-12,000 N/mm²

The relatively high density gives Redwood:

• Good screw holding capacity
• Improved impact resistance
• Better load-bearing properties

The wood fibres themselves tend to be more tightly packed than Spruce, contributing to greater strength.

Why Redwood Machines Better

The machining quality of Redwood is largely due to the balance between density and fibre cohesion.

The wood fibres remain relatively stable during cutting.

As cutting tools pass through the timber:

• Fibres sever cleanly
• Reduced tear-out occurs
• Sharper profiles are produced

This is especially important when creating:

• Decking grooves
• Chamfers
• Mouldings
• Decorative profiles
• Cladding rebates

Spruce, by comparison, often produces a slightly fuzzier machined surface.

This is why most premium machined products utilise Redwood.

Weaknesses

Despite its advantages, Redwood has limitations.

Heartwood Treatment Resistance

While sapwood treats exceptionally well, the heartwood is more resistant to preservative penetration.

This creates variation in treatment effectiveness depending on board composition.

Drying Checks

The relatively high density can result in:

• End checking
• Surface splitting
• Resin bleed

particularly when drying is poorly controlled.

Norway Spruce (Picea abies)

Species Overview

Norway Spruce forms the backbone of European fencing and construction industries.

In the timber trade, it is commonly sold as Whitewood.

Unlike Scots Pine, Spruce contains very little resin and possesses a more uniform cellular structure.

Cellular Characteristics

Spruce tracheids are generally thinner walled.

The species also contains:

• Smaller resin systems
• Lower extractive levels
• Less dense latewood zones

As a result, Spruce exhibits:

• Lower density
• Reduced strength
• Improved flexibility

Compared with Redwood.

Density

Typical density:

380 to 470 kg/m³

This lower density explains many of Spruce’s desirable fencing characteristics.

Why Spruce Splits Less

Fence manufacturers often prefer Spruce because of how the fibres behave during drying.

The species develops lower internal drying stresses than Scots Pine.

This reduces:

• End splitting
• Surface checking
• Shake formation

This leads to:

• Higher manufacturing yields
• Better consistency
• Reduced waste

For a fencing manufacturer producing thousands of fence panels, these benefits are significant.

Structural Applications

Spruce dominates C16 production because it achieves reliable structural performance whilst remaining economical.

Typical applications:

• Roof trusses
• Stud walls
• Garden buildings
• Timber framing

The lower density also makes handling easier on site.

Limitations

The major weakness of Spruce is treatment uptake.

The wood structure contains fewer pathways for preservative movement.

Consequently:

• Penetration depths are reduced
• Durability depends heavily on surface protection

Without treatment, Spruce has poor natural durability.

Douglas Fir (Pseudotsuga menziesii)

The Engineering Softwood

Douglas Fir is frequently regarded as the highest performing structural softwood available commercially.

Unlike Pine or Spruce, Douglas Fir evolved in mountainous regions where trees must support enormous heights and withstand extreme climatic loads.

As a result, it produces exceptionally strong timber.

Density

Typical density:

510 to 590 kg/m³

Bending strength:

85-120 N/mm²

Modulus of Elasticity:

12,000-14,000 N/mm²

These values often exceed both Redwood and Spruce.

Fibre Structure

Douglas Fir develops:

• Long fibres
• High latewood percentages
• Excellent fibre alignment

This combination creates:

• High stiffness
• Superior beam strength
• Reduced deflection

making it ideal for:

• Long-span structures
• Pergolas
• Feature beams
• Structural landscaping

Natural Durability

Douglas Fir heartwood contains significant levels of natural extractives.

These compounds:

• Reduce fungal attack
• Slow moisture absorption
• Improve weather resistance

without relying entirely on preservative treatment.

European Larch (Larix decidua)

The Naturally Durable Softwood

Among traditional softwoods, Larch possesses some of the highest natural durability characteristics.

The species evolved in exposed alpine environments and developed substantial resin production as a defensive mechanism.

Density

Typical density:

550-650 kg/m³

This places Larch at the upper end of the softwood density spectrum.

Resin Content

Larch contains extensive resin systems throughout the wood.

The resins perform several functions:

• Moisture exclusion
• Biological defence
• Fungal resistance

These characteristics explain why untreated Larch survives outdoors significantly longer than untreated Spruce.

Mechanical Performance

The dense fibre structure provides:

• Excellent wear resistance
• Strong screw holding
• High impact strength

making it well suited to:

• Decking
• Cladding
• Coastal installations
• Architectural landscaping

Stability Challenges

The same density that improves durability can create movement issues.

Internal growth stresses often produce:

• Twisting
• Bowing
• Surface checking

Proper kiln drying is therefore critical.

Species Comparison for Real-World Applications

Premium Machined Timber

Winner: Scandinavian Redwood

Because of:

• Excellent fibre cohesion
• Superior treatment uptake
• Attractive appearance
• Consistent machining quality

Fence Panels

Winner: Spruce

Because of:

• Lower density
• Reduced splitting tendency
• Lower cost
• Attractive pale finish

Structural Timber

Winner: Douglas Fir

Because of:

• High stiffness
• Exceptional bending strength
• Superior load-bearing performance

Natural Durability

Winner: Larch

Because of:

• High resin content
• Dense heartwood
• Superior resistance to moisture and fungal attack

Best Overall Landscaping Timber

For most UK landscaping applications, pressure-treated Scandinavian Redwood remains the benchmark.

Its unique combination of treatment permeability, dimensional stability, structural capability and machining performance makes it arguably the most versatile softwood available to merchants, landscapers and contractors alike. While Spruce dominates fencing manufacture for economic reasons, Redwood continues to be the species of choice wherever appearance, profiling quality and long-term performance are priorities.

By Giordan Gosling