A lettuce seedling is the juvenile plant that emerges from the seed. Identifying these tiny sprouts is important for gardeners, allowing for timely thinning and accurate weeding in the early stages of growth. The visual characteristics of the seedling change rapidly, transitioning from simple seed leaves to the complex structure of the mature plant.
The First Pair: Cotyledons
The very first leaves to emerge above the soil are the cotyledons, or seed leaves, which bear little resemblance to the mature lettuce plant. These initial leaves are small, smooth, oblong, or slightly paddle-like in shape. They are a uniform, bright green color and emerge as a symmetrical pair opposite each other on the delicate stem.
The cotyledons’ primary function is to serve as the plant’s first energy source, drawing on stored nutrients within the seed. Once unfurled, they begin photosynthesis to fuel early growth. These temporary organs will eventually yellow, wither, and drop off once the plant establishes its permanent foliage.
Identifying the True Leaves
The definitive identification of a lettuce seedling occurs with the appearance of the true leaves, which grow from the central growing point between the cotyledons. Unlike the smooth seed leaves, the true leaves possess the texture and shape characteristic of the lettuce species. They are often slightly crinkled, dimpled, or bubbly, and their edges may display small lobes or serrations.
These leaves quickly begin to form the plant’s characteristic rosette shape, sitting low to the ground. The true leaves are the plant’s permanent photosynthetic organs, taking over the energy production role from the temporary cotyledons. Subsequent true leaves will be miniature versions of the adult foliage.
Early Visual Variations Among Lettuce Types
While all lettuce seedlings start with similar cotyledons, slight variations in the true leaves can distinguish major lettuce types early on. Red-leaf varieties, such as ‘Red Sails’ or ‘Lollo Rossa,’ exhibit a reddish or purplish tint along the leaf margins or veins upon the emergence of their true leaves. This coloration is due to anthocyanin pigments.
Romaine lettuce seedlings tend to develop true leaves that are slightly narrower and more upright, hinting at the mature plant’s elongated, vertical form. In contrast, butterhead and looseleaf types show broader, more rounded true leaves that spread out closer to the soil surface. Recognizing these differences allows for variety-specific management.
Distinguishing Lettuce Seedlings from Common Weeds
Lettuce seedlings can be confused with certain common garden weeds, but specific visual cues help distinguish them. Lettuce cotyledons are round or oval and a vibrant, uniform green, while the true leaves form a single, clean rosette without a distinct central stem. The stem of a lettuce seedling is pale green and smooth.
In contrast, common lambsquarters (Chenopodium album) has narrowly oblong cotyledons that may have a purple tint on the underside and a mealy, whitish coating on the emerging true leaves. Common chickweed (Stellaria media) has small, oval cotyledons, and its true leaves grow in opposite pairs on a stem with a line of fine hairs. Weeds frequently appear scattered haphazardly, whereas lettuce sprouts are found in predictable, orderly rows where seeds were sown.