Jack pine

Leaves

Form

• Needles evergreen
• In bundles of 2
• Straight or slightly twisted, stiff
• Sharp-pointed, spread apart
• Edges toothed
• Bundle-sheath persistent

Length

• 2–4 cm

Colour

• Light yellowish-green

Buds

Form

• Blunt-pointed, resinous

Length

• To 15 mm

Colour

• Pale reddish-brown

Twigs

Form

• Slender, ridged and grooved
• Vigorous shoots on young trees usually with 1 or more intermediate nodes bearing loose whorls of side branches

Colour

• Yellowish-green becoming dark greyish-brown in second season

Seed cones (mature)

Form

• Variable in shape
• Oblong to conical, asymmetrical
• Straight or curved inward
• Stalkless, usually pointing forward
• Often in clusters of 2 or 3 at nodes
• Usually remaining closed and persistent on the tree for 10–20 years

Length

• 3–7 cm

Colour

• Yellowish-brown when mature

Structure

• 80 scales, thickened at the tips
• Smooth (sometimes with a minute prickle)
• Held closed by a resin bond

Timing

• Open when exposed to heat from a wildfire or sometimes from direct sunlight on warm days

Seeds

Form

• Often ridged

Length

• Seed 3 mm
• Seed wing about 10 mm

Colour

• Dark brown or black

Seedlings

Form

• 3–6 cotyledons, toothless
  

Lenght

• 12–24 mm

Bark

Form

• Thin when young, becoming flaky
• With age furrowed into irregular thick plates

Colour

• Reddish-brown to grey when young, becoming dark brown

Wood

Texture

• Moderately hard and heavy, weak

Colour

• Light brown

Uses

• General construction, wood pulp, railway ties, poles, pilings, and mine timbers

Size

Height

• To 20 m, occasionally larger

Diameter

• To 30 cm

Maximum age

• 150 years

Tree form

Open-grown

Trunk

• Tapered

Crown

• Conical, open
• Branches ascending, arching

Forest-grown

Trunk

• Slender, straight, with little taper

Crown

• Short

Root system

• Wide-spreading, moderately deep
• Often with a taproot

Habitat

Site

• Coarse sands, shallow soils, and rock out-crops, permafrost
• On poor soils and rocky sites, tree short, often twisted, with long stout branches, some dead or dying, giving the crown an unkempt appearance
• After extensive fires, jack pine may occupy all sites from ridge tops to muskegs

Light tolerance

• Intolerant of shade

Associated species

• Grows in pure stands or mixed with other shade-intolerant species such as white birch, trembling aspen, balsam poplar, red pine, and tamarack
• Shade-tolerant species such as black spruce, white spruce, and balsam fir often form the understory

Range

Most widely distributed pine in Canada