Leaf Types and Arrangement Persistence Deciduous. A perennial plant is one that lives more than two years. Leaves that fall off at the end of a growing period are called deciduous. Examples are found in maples (Acer), birches (Betula), and dogwoods (Cornus).
and some monocots have pinnate venation with Swiss cheese plant (Monstera) as an example. Leaf Attachment Petiolate. The leaf blade is attached to the stem by a stalk called a petiole (d).
Evergreen. Leaves that remain on a plant for more than a year are called evergreen. Pines (Pinus), spruces (Picea), rhododendrons (Rhododendron) are examples.
Sessile. When the leaf blade is attached directly to the stem without a petiole, it is sessile (a, f, n).
Leaf Types
Simple. A simple leaf has one blade, which may be broad (i) as in the maple leaf shown, narrow, or needlelike (a).
Conifer. The leaves of conifers are needle-like (a) as on pines or scale-like as on junipers (Juniperus). They are usually evergreen, although some conifers have deciduous leaves such as larches (Larix). Each conifer leaf has a single vein. Ginkgo. This unique plant (see 72) has fan-shaped leaf blades (c) with dichotomous venation in which the veins branch into two equal or unequal lengths. The leaves are deciduous and shed within a 24-hour period. Dicot. Most dicot blades have pinnate (feather-like) venation (e) in which major veins diverge from one large mid-vein, with smaller network connections between. Some dicot blades have palmate (hand-like) venation (i) where several large veins diverge from the petiole to the margins. Some dicots have parallel venation. An example is plantain (Plantago lanceolata). Monocot. Most Temperate Zone monocots have narrow strap-shaped blades (f) with sheathing bases (g) surrounding the stem (h). With parallel venation, major veins arise at the base, remain more or less parallel, and converge at the tip with small vein interconnections. Some monocot leaf veins converge at the leaf margins instead of the tip, such as philodendron (Philodendron)
Leaf Form
Compound. A compound leaf is one that has two or more blade-like leaftlets such as sumac (Rhus, j, pinnately compound) or clover (Trifolium, k, palmately compound) attached to a petiole (d). Leaf Arrangement Opposite. Two leaves (l) emerge opposite each other on a stem. The example shown is milkweed (Asclepias syriaca). Generally maples, ashes, dogwoods, and members of the honeysuckle Family (Caprifoliaceae) have opposite leaves. MAD Cap is an easy way to remember. Alternate. In an alternate arrangement, single leaves (m) are attached spirally along the stem. Lamb’s quarters (Chenopodium album) is shown (see 88). Most genera have alternate leaves. Whorled. In a whorled arrangement, several leaves (n) emerge together around a stem node. Michigan lily (Lilium michiganense) is the example shown (see 128).
COLOR CODE blue-green: green: dark green: yellow: light green: orange: red:
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blade (a) shoot peg (b), petiole (d), blade (l, n) blade (e) blade (c) blade (f, m), sheath (g), stem (h), leaets(k) blade (i) leaets (j)