A cotyledon is the first leaf or pair of leaves that emerges when a seed germinates. Cotyledons are not true leaves — they are embryonic structures packed inside the seed before germination, and they serve as the plant’s initial energy source before photosynthesis begins. In home gardening, the cotyledon stage is the primary harvest window for both sprouts and microgreens.
Most plants used for microgreens and sprouts are dicots (two cotyledons) or monocots (one cotyledon). Dicot cotyledons tend to be broad, tender, and mild-flavored — sunflower, radish, and broccoli microgreens are harvested at this stage. Monocot cotyledons, like those of wheatgrass, emerge as a single blade. The flavor, color, and texture of a microgreen at the cotyledon stage differ from the same plant harvested later, because true leaves develop different cell structures and chemical profiles.
The transition from cotyledon to true leaf is the dividing line between a microgreen and a baby green. Microgreens are typically harvested just as the first true leaves begin to emerge, when the cotyledons are fully expanded and the stem is tall enough to cut. Harvesting at this stage balances yield, tenderness, and flavor concentration. Waiting longer produces a larger plant but one that is tougher and less concentrated in the compounds that give microgreens their characteristic intensity.