Identifying and classifying a plant by its leaves is a helpful way to begin researching plant types. Coniferous, deciduous and tropical trees, for example, have particular leaf structures that help water reach the root system or sunlight and oxygen circulate through the plant, as it does in the photosynthetic process. To identify and classify leaves, start with a field-guide book or take samples of fallen leaves to research back at home.
Identify whether a leaf is simple or compound. If one leaf grows off one stem, it has a "simple" structure. If one leaf stem carries three or more leaves, the plant has a "compound" leaf structure. Leaves with "teeth," or a serrated, jagged edge, help classify the type of plant, like an elm tree. A lobed leaf has rounded edges, such as the leaves of the gingko tree.
Coniferous trees, or evergreen trees, have thin green needles, a type of leaf. While it looks like evergreen trees and shrubs never shed their leaves, old needles fall to the ground a few at a time. Needles are tougher than deciduous leaves and do not lose water as quickly, which allows them to stay alive in frigid winter temperatures.
Evergreen species such as pines, spruces and firs have leaf characteristics that are useful for identification. Pines have long, slender needles in bundles of two to five; spruce trees have four-sided, small, pointy single needles; firs have short, flat single needles. The Western hemlock has a distinguished leaf type: short needles with white stripes on the underside.
Deciduous trees and shrubs shed their leaves in the fall. Tree leaves change to brilliant colors before falling. Identify the leaves by their broad shape and either simple or compound structure. Some deciduous tree types include the maple and the oak. Deciduous bushes, such as viburnum or hazel bushes, are flowering shrubs that shed their leaves.
Deciduous trees are divided into five groups. Leaves can be simple and opposite; simple and alternate (long and narrow); simple and alternate (wide); compound and opposite; or compound and alternate. A simple and opposite structure has a one leaf on each side of a branch. In a simple alternate structure, leaves sprout down the branch like a zipper. The structures are further classified into wide or narrow leaf shapes.
Waxy or Glossy
Identifying whether a leaf is glossy or waxy helps identify the type of plant. Tropical plants, such as palm trees, usually have waxy-coated leaves so that water sticks more to the leaf and can drip into the tree's roots. Oak trees, which are deciduous, have semi-glossy leaves with a silvery backside.
- North Dakota State University Agriculture and University Extension: A Guide to Deciduous Tree Knowledge
- Colorado State University Extension: Plant Structures: Leaves
- Colorado State University Extension: Identifying Trees and Shrubs
- Minnesota Department of Natural Resources: Young Naturalists: Trees (By Dawn A. Flinn)
- National Park Service: Key to the Coniferous Trees in Glacier