Fir

Firs are evergreen coniferous trees belonging to the genus Abies (Latin: [ˈabieːs] ) in the family Pinaceae. There are approximately 48–65^{[3] [4]} extant species, found on mountains throughout much of North and Central America, Eurasia, and North Africa. The genus is most closely related to Keteleeria , a small genus confined to eastern Asia.^[5]

The genus name is derived from the Latin "to rise" in reference to the height of its species.^[6] The common English name originates with the Old Norse fyri or the Old Danish fyr.^[7]

They are large trees, reaching heights of 10–80 metres (33–262 feet) tall with trunk diameters of 0.5–4 m (1 ft 8 in – 13 ft 1 in) when mature. Firs can be distinguished from other members of the pine family by the way in which their needle-like leaves are attached singly to the branches with a base resembling a suction cup, and by their cones, which, like those of cedars, stand upright on the branches like candles and disintegrate at maturity.

Identification of the different species is based on the size and arrangement of the leaves, the size and shape of the cones, and whether the bract scales of the cones are long and exserted, or short and hidden inside the cone.

• A. alba – the underside of leaves have two whitish strips formed by wax-covered stomatal bands, while their bases are shaped like suction cups.
  A. alba – the underside of leaves have two whitish strips formed by wax-covered stomatal bands, while their bases are shaped like suction cups.
• A. grandis foliage – upper side of the leaves, showing the leaves lying flat either side of the shoot
  A. grandis foliage – upper side of the leaves, showing the leaves lying flat either side of the shoot
• Foliage of A. pinsapo showing the radial leaf arrangement in this species
  Foliage of A. pinsapo showing the radial leaf arrangement in this species
• Most firs are inbetween the two extremes of flat and radial, with an intermediate arrangement, often with longer leaves at the sides, and shorter leaves above the shoot; here, A. mariesii in Japan
  Most firs are inbetween the two extremes of flat and radial, with an intermediate arrangement, often with longer leaves at the sides, and shorter leaves above the shoot; here, A. mariesii in Japan

Firs can be distinguished from other members of the pine family by the unique attachment of their needle-like leaves to the twig by a base that resembles a small suction cup. The leaves are significantly flattened, sometimes even looking like they are pressed, as in A. sibirica .

The leaves have two whitish lines on the bottom, each of which is formed by wax-covered stomatal bands. In most species, the upper surface of the leaves is uniformly green and shiny, without stomata or with a few on the tip, visible as whitish spots. Other species have the upper surface of leaves dull, greyish green or bluish to silvery (glaucous), coated by wax with variable number of stomatal bands, and not always continuous. An example species with shiny green leaves is A. alba , and an example species with matt waxy leaves is A. concolor .

The tips of leaves are usually more or less notched (as in A. firma ), but sometimes rounded or dull (as in A. concolor , A. magnifica ) or sharp and prickly (as in A. bracteata , A. cephalonica , A. holophylla ). The leaves of young plants are usually sharper.

The leaves are arranged spirally on the shoots, but by being twisted at their base, the way they spread from the shoot is diverse; in some species comb-like ('pectinate'), with the leaves flat on either side of the shoot (e.g. A. alba , A. grandis ), in others, the leaves remain radial (e.g. A. pinsapo )^[8]

Foliage in the upper crown on cone-bearing branches is different, with the leaves shorter, curved, and sometimes sharp.^[9]

• Intact and disintegrated Bulgarian fir cones
  Intact and disintegrated Bulgarian fir cones
• Immature cones of some species are green; here Manchurian fir Abies holophylla
  Immature cones of some species are green; here Manchurian fir Abies holophylla
• Disintegrating cones of Manchurian fir
  Disintegrating cones of Manchurian fir
• Pindrow fir Abies pindrow with dark purple cones
  Pindrow fir Abies pindrow with dark purple cones
• Caucasian Fir Abies nordmanniana young cones with reddish scales and yellow-green bracts
  Caucasian Fir Abies nordmanniana young cones with reddish scales and yellow-green bracts
• Noble fir Abies procera, with five heavy (20 cm, approx 0.5 kg each) cones, three erect, and two hanging where their weight has caused the branch to twist
  Noble fir Abies procera, with five heavy (20 cm, approx 0.5 kg each) cones, three erect, and two hanging where their weight has caused the branch to twist

Firs differ from other conifers in having erect, cylindrical cones 5–25 cm (2–10 in) long that disintegrate at maturity to release the winged seeds. In contrast to spruces, fir cones are erect; they do not hang, unless heavy enough to twist the branch with their weight.

The mature cones are usually brown. When young in summer, they can be green:

A. grandis , A. holophylla

or reddish:

A. alba , A. cephalonica , A. nordmanniana

or bloomed pale glaucous or pinkish:

A. numidica , A. pinsapo

or purple to blue, sometimes very dark blue, almost black:

A. forrestii , A. fraseri , A. homolepis , A. lasiocarpa , A. pindrow .

Many species are polymorphic in cone colour, with different individuals of the same species producing either green or purple cones:

A. concolor , A. koreana (usually purple, rarely green, such as the cultivar 'Flava'), A. magnifica (usually green, occasionally purple), A. nephrolepis (f. chlorocarpa green), A. sibirica , A. veitchii (f. olivacea green)^[8]

The cone scale bracts can be short and hidden in the mature cone, or long and exposed ('exserted'); this can vary even within a species, e.g. in Abies magnifica var. magnifica, the bracts are hidden, but in var. critchfieldii and var. shastensis, they are exserted. The bracts scales are often a different colour to the cone scales, which can make for a very attractive combination valued in ornamental trees.

The oldest pollen assignable to the genus dates to the Late Cretaceous in Siberia, with records of leaves and reproductive organs across the Northern Hemisphere from the Eocene onwards.^[10]