flatleaved

Flatleaved is a descriptive term used in botany and horticulture to indicate that a plant’s leaves are flat, with the lamina lying in a single plane. This contrasts with leaves that are folded, curled, lobed, or otherwise non-planar. The descriptor applies to both simple and compound leaves, provided the blade portion is spread out in a relatively flat form. In practice, flatleaved plants tend to have leaves whose morphology emphasizes a broad, even blade with minimal curvature, though margins may vary from entire to toothed.

The term is descriptive rather than taxonomic and appears in field notes, floras, and horticultural guides. It is commonly used in the common names of culinary herbs to distinguish flat, smooth leaves from curly or crinkled varieties. A well-known example is flat-leaved parsley (Petroselinum crispum), whose flat leaf blades are preferred for flavor and appearance compared with curly-leaved varieties. Other species may be described as having flat leaves in cultivar descriptions or species diagnoses when the flat blade is a stable characteristic.

Leaf flatness can be influenced by developmental stage, light, and nutrient status, so observers may note that the leaf plane is most evident in mature, well-formed leaves. Flatleaved morphology is one of several standard leaf-shape descriptors used in plant identification and description.