All but 15 typesof conifers are evergreen, one of the familiar characteristics of this group of plants. They grow with a straight, central trunk bearing circles of horizontal branches, and the branching may become increasing complex as the tree gets older. Conifers also have a wide variety of distinctive bark. This outer layer typically starts out smooth, and somestay that way, like lacebark pine Pinus bungeana or common yew Taxus baccata, with bark that peels or flakes off the older layers. Otherslike redwood Sequoia sempervirens and incense cedar Calocedrus decurrens develop fibrous bark that grows in vertical strips. Still other conifers have thick, rough, blocky bark that can show a variety of colors, such as Douglas fir Pseudotsuga menziesii and Cedar of Lebanon Cedrus libani.
Contemplating Cones: The name conifer means “cone-bearer,” and the classification of conifers is often based on the structure of their cones—or whether they have them, since not all conifers do. Those with cones have two types, a pollen cone and a seed cone. The pollen cones are soft and small, and they contain pollen sacs filled with pollen grains. Seed cones are the much larger, often woody, and easily recognized female cones that develop the seeds. These cones are usually made up of a spiral arrangement of little plates called scales. Pollination is often achieved by wind or water, carrying pollen grains to a seed cone. At maturity, seed cones may release their seeds by opening up as the scales spread apart; the scales shattering; or being burned by fire and snapping open. There are also conifers with seed cones that soften and change color to entice wildlife to eat them and spread the seeds, including podocarpus and juniper.
A Needling Question: Conifers are divided into many subgroups, including pines, firs, larches, and spruces. How can you tell them apart? There are some tricks of the trade to help identify which is which. Pine and larch trees grow needles—which are modified leaves—in bundles. Pines have two to five needles per bundle, while larches have 10 or more needles to a bundle. When needles are removed from a fir tree, a small, round scar remains on the twig. If they are removed from a spruce, a small, woody peg is left standing out from the branch. And then there are the conifers that surprise you, since they have broad leaves instead of needles, like the Kauri pine Agathus robusta and the gingko tree Gingko biloba, which is considered one of the most primitive of the conifers.
