Pinaceae - pine family
Leaves. Pinaceae leaves, often called needles, occur singly in a spiral-like fashion around the twig (Abies, Picea, and Tsuga) or in clusters (Larix and Pinus). The three species with solitary needles can be distinguished from each other by the way the leaves attach to the twig. Abies needles have expanded bases that leave [no pun intended] a round scar on the twig; each Tsuga leaf attaches to a short peg via a thin petiole; and Picea leaves also attach to short "pegs" called sterigmata (singular: sterigma) but do not have petioles.
   Leaves of Pinus occur in clusters, called fascicles, of 2, 3, or 5; Larix leaves are in clusters of 8 or more and, unlike leaves of the other 4 genera of Pinaceae on MDI, they are deciduous (i.e., they fall from the tree before winter and new ones grow each spring).
Pollen cones. Seed cones (see below) are well known although not usually identified to species by the casual observer. Pollen cones, on the other hand, are almost always overlooked. They are noticed only in late spring, when the yellow pollen they bear coats automobiles, lakes and ponds, and puddles on sidewalks and driveways. A conspicuous ring of yellow remains on the ground after the water in one of these puddles has evaporated. Unlike seed cones, pollen cones grow in clusters, often more than a dozen together (see right-hand image of pitch pine below). Also unlike the woody seed cones that remain on the tree for sometimes several years, pollen cones are relatively soft and by mid-summer have fallen to the ground.
Seed cones. Seed cones are by far more frequently observed than pollen cones. They are much larger (sometimes more than 6 inches long) than pollen cones and, with the exception of those of balsam fir (Abies balsamea, see notes for this species below), persist as a woody unit for many years, either on a tree or on the ground.

Mount Desert Island is home to 11 species in 5 genera that grow without cultivation. Click on a link below or scroll down for more information.
   Abies (1 species)
      Abies balsamea - balsam fir (common [see note 1 at bottom of page])
   Larix (1 species)
      Larix laricina - American larch, hackmatack, tamarack (occasional)
   Picea (3 species)
      Picea glauca - white spruce (common)
      Picea mariana - black spruce (occasional)
      Picea rubens - red spruce (common)
   Pinus (5 species)
      Pinus banksiana - jack pine (occasional)
      Pinus resinosa - red pine (occasional)
      Pinus rigida - pitch pine (occasional)
      Pinus strobus - eastern white pine (common)
      Pinus sylvestris - Scotch pine (uncommon)
   Tsuga (1 species)
      Tsuga canadensis - eastern hemlock (occasional)

Abies (fir)

Abies balsamea (balsam fir) is most easily identified by noting the expanded base of each leaf.

The abaxial (lower) surface of A. balsamea leaves has prominent white lines (see image below left), much like that of Tsuga canadensis leaves (see eastern hemlock images near bottom of this page). However, the branching pattern of balsam fir twigs is quite symmetrical (see image below left), unlike that of eastern hemlock. Many people think that the leaves of a balsam fir branch lay in one plane, and that is generally true of trees that grow in more or less shaded areas of low elevation. However, in exposed and/or higher elevation sites, the leaves often curve noticeably (see image below right) and can be mistaken for those of spruce if one does not look carefully.

The seed cones of Abies balsamea grow erect on branches (vs. pendulous for other members of the Pinaceae) and release their seeds when the cone scales separate from the cone axis (vs. other Pinaceae cones, which remain intact). A good place to see balsam fir seed cones is on the top of Cadillac Mountain along the path leading from near the gift shop to the south ridge trail.

Larix (American larch, hackmatack, tamarack)

Larix laricina (American larch, hackmatack, or tamarack), a species with fascicles of eight or more leaves (see image of emerging leaves below left), is Maine's only deciduous conifer (i.e., American larch loses all of its leaves each fall). Many American larch grow along Route 102A between Wonderland and Ship Harbor, particularly on the north side of the road (i.e., the side away from the ocean).

Picea (spruce)
Three species of spruce are native to Mount Desert Island: Picea glauca (white spruce), P. mariana (black pine), and P. rubens (red spruce). As mentioned near the top of this page, Picea leaves are attached to short peg-like projections called sterigmata (see image below). At the base of each sterigma is an angle that forms an imaginary dividing point between the sterigma that diverges from the twig and the twig ridge that runs lengthwise along the twig for a short distance. The presence or absence of very short hairs on the twig and the shape of the twig ridges are important features used in identifying the species.
   Twigs of white spruce (P. glauca) are completely devoid of hairs; both black spruce (P. mariana) and red spruce (P. rubens) have few to many hairs on the twig. Differentiating between black and red spruce is more problematic, and it is thought that there may be hybridization between them or even that they may not be distinct species. The amount of rounding of the cross-section of the twig ridges, called "twig ridge inflation", is often used to differentiate red and black spruce (when each is thought to be a valid species). Red spruce has very rounded cross-sections of twig ridges. (Imagine a hot dog cut lengthwise and then one of those pieces laid with the cut side touching the twig.) Black spruce has a flat twig ridge cross-section. (Imagine if the twig ridge had been filled with air and was then deflated with a pin prick.) There are varying degrees of "inflation", one factor leading to a hypothesis of hybridization.

Picea glauca (white spruce) is relatively easy to distinguish from the other two species of spruce that are native to Mount Desert Island. In addition to the absence of hairs on the twig mentioned above (and the image above is of a white spruce twig), its seed cones (see image below) are conspicuously longer and more elongate than the shorter, nearly spherical ones of black and red spruce. Picea glauca is sometimes called cat spruce because a bruised twig can smell distinctly [di-stink-tly?] like a cat box. However, some trees have a stronger odor than others, and a fair number of people seem unable to detect the smell.

Picea mariana (black spruce) is the common spruce species found in a heath, as in the image below taken across Route 102A from the Wonderland trailhead.

Picea rubens (red spruce). The hairs on the twig (see image below left) and the "inflated" twig ridges (same image) distinguish red spruce from the other two Picea species. Like black spruce, red spruce has nearly globular seed cones (see image below right).
 

Pinus (pine)
Five species of pines are native or have become naturalized on Mount Desert Island: Pinus banksiana (jack pine), P. resinosa (red pine), P. rigida (pitch pine), P. strobus (eastern white pine), and P. sylvestris (Scotch pine). Of these five, only the Scotch pine is not native to Mount Desert Island; that is, it was introduced to the island by post-European-contact humans. Seed cones of pine trees, often simply referred to as "pine cones", differ from those of the other genera in the pine family by having scales with a thickened portion, called an umbo, at (Pinus strobus, eastern white pine) or near (the remaining species) their tips. (Note: please do not make the mistake of applying the term "pine cone" to the seed cones of all genera in the pine family. I once heard someone point out the "pine cones on the ground under the spruce trees"!)

Pinus banksiana (jack pine) has fascicles (clusters) of two short leaves (needles) and seed cones that are often slightly curved (see image below left). As in other species of Pinus, the pollen cones are clustered (see bottom of image below right). Several jack pines can be seen near the south end of the parking area on Route 3 across from the Canon Brook trailhead.

Pinus resinosa (red pine) is a species with fascicles of two long leaves. These leaves usually break cleanly when folded back against themselves (image at lower left). When the seed cones fall from the tree, they leave behind several scales on the tree, yielding what are called "hollow-based" cones (lower left). The bark (below middle) is not furrowed as is the bark of Pinus strobus (white pine). Overall, the trees branches have a bottle-brush look (lower right).

Pinus rigida (pitch pine), Maine's only species with fascicles of three leaves (see image at lower left), is abundant along the left side of the park loop road where it overlooks Sand Beach. The thickened portion, called an umbo, of each cone scale bears a sharp prickle (see image at lower left). As in other species of Pinus, the pollen cones are clustered (see image below right).

Pinus strobus (eastern white pine) is the most common species of pine on Mount Desert Island and is Maine's only species with fascicles of five leaves (see image at lower left). A cross-section of a fascicle reveals five triangular needles that have bands of stomata (pores for gas exchange) on the two inner surfaces. A waxy substance makes these appear as pairs of whitish stripes in the photo. Eastern white pine has the longest seed cones in the genus in Maine (see image below center). It is not unusual to see very straight trunks with their characteristic bark (see image at lower right). A particularly large eastern white pine can be seen on the west edge of the carriage road on the west side of Eagle Lake. The name Pinus strobus was given to this species by Carl Linnaeus in the first edition (1753) of his Species Plantarum, the beginning point for plant names as established by the International Code of Botanical Nomenclature.

Pinus sylvestris (Scotch pine), like jack pine, has fascicles of two short leaves. Unlike the fairly straight leaves of jack pine, however, the needles of Scotch pine are somewhat to quite twisted (see image at lower left). By far the most distinctive feature of this species is the orange-salmon color of the young bark (see image at lower right). Several Scotch pines grow along the right side of the park loop road near Beaver Dam Pond, soon after entering the road from Sieur de Monts.

Tsuga (hemlock)

Tsuga canadensis (eastern hemlock) is frequent along the appropriately named Hemlock Trail, which begins at the end of the Sieur de Monts parking lot that is furthest from the nature center. The abaxial (lower) surface of its leaves (see image at lower left), like that of Abies balsamea leaves, is conspicuously white. A distinctive feature of T. canadensis is the presence of leaves laying lengthwise along the upper side of the twig (see image at lower right). Note that when you look down at these leaves you are looking at their abaxial surface.

A particularly good place to see Tsuga canadensis is in the Sieur de Monts area. Follow Route 3 south from the village of Bar Harbor past Jackson Lab and watch on the right for a sign for Sieur de Monts. Follow the signs to the parking lot for the Acadia National Park nature center and the Wild Gardens of Acadia. Immediately upon entering the parking lot, look to your right and you will see a wide trail. That is the Hemlock Trail and after a short distance, it passes under many hemlock trees.

Note:
   1. Frequency designations are from the paper "Vascular flora of the Acadia National Park region, Maine" by Craig W. Greene, Linda L. Gregory, Glen H. Mittelhauser, Sally C. Rooney, and Jill E. Weber, published in the spring 2005 issue (vol. 107, No. 930) of Rhodora: Journal of the New England Botanical Club.