When a lettuce seed germinates, the tiny plant that emerges is called a seedling, representing the initial stage of growth until the first set of mature leaves develops. Identifying these young plants is necessary for successful gardening, especially when distinguishing them from weeds. The visual progression is marked by two distinct types of leaves that appear sequentially, providing different clues to the plant’s identity.
The First Sign: Cotyledons
The very first leaves to emerge above the soil are called cotyledons, or seed leaves. These leaves are part of the plant embryo and serve as the initial food source, using stored energy to fuel the seedling’s early growth. Lettuce cotyledons are small, simple, and uniform in appearance across all varieties, whether they are destined to become Romaine or Butterhead lettuce. They present as a pair of smooth-edged, bright green leaves that are either oval or slightly elongated in shape, appearing opposite each other on a slender stem. Their generic look means they do not resemble the mature lettuce leaves at all.
Developing Identity: True Leaves
Shortly after the cotyledons fully expand, usually within one to three weeks of germination, the first true leaves begin to appear from the center of the seedling. These true leaves are the second set to grow and are the first to resemble the foliage of the adult lettuce plant. They emerge from the growing point between the two cotyledons, signaling the start of the plant’s self-sustaining life through photosynthesis. True leaves differ significantly from the smooth, simple cotyledons; they are rougher in texture, often displaying slight crinkling, gentle serration, or minor lobes along the edges. As they grow, they become progressively larger and more textured, confirming the plant’s identity as Lactuca sativa. Initial signs of varietal characteristics, such as a looser growth habit or a reddish or bronze pigment on the leaf tips, may become visible.
Distinguishing Features and Varieties
The development of the true leaves is the most reliable visual marker for identifying a lettuce seedling. Many common garden weeds have cotyledons that are pointy, slender, or highly specialized, setting them apart from the uniformly oval lettuce cotyledons. Waiting for the true leaves to appear reduces the risk of accidentally pulling out a desirable crop, as they are miniature versions of the adult plant’s recognizable foliage. Young lettuce plants naturally adopt a rosette growth pattern, where the leaves grow in a circular, compact arrangement close to the soil surface, without forming a tall central stalk. Subtle differences in variety emerge as the true leaves mature, such as the thicker, slightly cupped leaves of a future Butterhead or the more openly growing, deeply lobed leaves of a loose-leaf type.