The Pinaceae

The family Pinaceae includes much more than pine trees. Pine trees are members of the genus, Pinus, only one of the genera in the Pinaceae.

Genera included in the Pinaceae include:

  • Pinus (pines)
  • Abies (fir)
  • Picea (spruce)
  • Tsuga (hemlock)
  • Pseudotsuga (Douglas-fir)

All members of the Pinaceae have alternate leaves, and the leaves do not cloak the branches. The trees are moneocious, bearing both pollen cones and seed cones on the same plant.

 

Genus Pinus

Pine fascicle diagram.
Longitudinal section of a very young pine fascicle with two foliage needles

In the genus Pinus, most foliage leaves (or foliage needles) are borne on short, determinate branches, rather than attaching directly to the main stem. These short, determinate shoots or branches produce a series of scale leaves, then they produce 1 to 5 foliage needles, then the shoot apex stops growing. This short shoot and its bundle of foliage needles is called a fascicle.

The scale leaves (labeled "bud scales" on the drawing shown here) are non-photosynthetic and typically wrap around the base of the foliage needles, forming a sheath. This structure is called...a sheath. Scale leaves that make up the sheath may remain wrapped around the foliage needles for a long time (until they wear away through age), or they may be deciduous, falling off early and leaving only the foliage needles attached to a bare peg of the stem of the short shoot.

 The images below show scale leaves and fascicles with needles and sheaths on a young tree of Pinus jeffreyi (Jeffrey pine).

Jeffrey pine scale leaves and fascicles.
Scale leaves and fascicles of Jeffrey pine (Pinus jeffreyi)

Check your understanding:

Below are photos of two pine species: Species "A" and Species "B".

Quiz pines

 

Genus Abies

Fir trees (genus Abies) are also in the Pinaceae.

  • Their needles are blunt and do not occur in fascicles.
  • Their seed cones stand upright near the top of the tree and fall apart on the tree, dropping cone scales individually. Therefore, you rarely find an intact seed cone on the ground.

Abies concolor

 

Genus Pseudotsuga

The genus Pseudotsuga is in the Pinaceae. This is the genus referred to a Douglas fir.

Its needles are not as blunt as fir needles, and its cones are pendent. The cones are recognizable by the three-lobed cone-scale bract that is exerted.

Cone of Pseudotsuga
Cone of Pseudotsuga (Douglas fir)

 

Genera: Picea and Tsuga

Spruce trees (genus Picea) and hemlock trees (genus Tsuga) are also in the Pinaceae. Species of both occur in California, but neither occur in Southern California. Therefore, we will not cover them this year.