15 Plant Morphology – Conifers

Both evergreen and deciduous leaves exhibit characteristic broad blades in angiosperms, and narrow needle, scale-like, or awl-shaped leaves in the conifers. Figure 15.1 illustrates  the different types of conifer leaves. Leaves may be borne singly on the shoot as in Picea spp. (spruce), in tufts or clusters as in Larix spp. (larch), or in fascicles (bundles) of 2-5 as in Pinus spp. (pines). The awl-shape and scale-like foliage of Juniperus spp. exhibits leaf dimorphism where a juvenile leaf form differs from the mature leaves of the same plant.

Dichotomous Key for Some Common Conifers. Click the links for plant images.

• • 1.a. leaves long, needle-like ……………………………………………………………………. go to 2
  • 1.b. leaves lanceolate, awl or scale-like, overlapping, not needle-like ……………………………………………………………………………………………………………….. go to 5
  • 2.a. needles in bundles or tufts ………………………………………………………………. go to 3
  • 2.b. needles borne singly ……………………………………………………………………….. go to 7
  • 3.a. needles in bundles of 2 to 5 …………………………………………………………….. go to 4
  • 3.b. needles deciduous, many in a tuft …………………………. Larix decidua [New Tab]^[1]
  • 4.a. 5 needles per bundle ……………………………………………… Pinus strobus [New Tab]^[2]
  • 4.b. 2 needles per bundle …………………………………………………………………….. go to 10
  • 5.a. scales imbricate (overlapping) cones small, upright………………… Thuja plicata [New Tab]^[3]
  • 5.b. scales imbricate, cones spherical or oval, opening along sutures at maturity ……………………………………………………………………………………………………………….. go to 6
  • 6.a. cones small, spherical; cone scales with a prominent point …………………………………………………………………… Cupressus nootkatensis [New Tab]^[4]
  • 6.b. cones larger, oval, cone scales thick, deeply pitted …………………………………………………………….. Sequoiadendron giganteum [New Tab]^[5]
  • 7.a. needles stiff and sharp, 4-sided ………………………………………………………. go to 8
  • 7.b. needles flat and pliable …………………………………………………………………… go to 9
  • 8.a. needles extremely sharp, new growth coated with bluish wax……………………………………………………. Picea pungens Glauca Group [New Tab]^[6]
  • 8.b. needles not extremely sharp, not coated with bluish wax …………………………………………………………………………………….. Picea abies [New Tab]^[7]
  • 9.a. needles dull green, 2 cm long, borne on short pegs that persist after the needles fall ………………………………………………………..Tsuga heterophylla [New Tab]^[8]
  • 9.b. needles shining green, 2 cm long, not borne on pegs …………………………………………………………………….. Pseudotsuga menziesii [New Tab]^[9]
  • 10.a. needles < 7 cm long …………………………………………………………………….. go to 11
  • 10.b. needles > 7 cm long …………………………………………… Pinus nigra [New Tab]^[10]
  • 11.a. needles dark green, 3-6 cm long, cone scales with a small recurved prickle ………………………………………………………………………………. Pinus contorta [New Tab]^[11]
  • 11.b. needles bluish green 5-7 cm long, slightly twisted, cone scales without a prickle ………………………………………………………………….. Pinus sylvestris [New Tab]^[12]