Germination is when a seed activates, absorbing water and energy to initiate growth. For lettuce, this involves the seed swelling and pushing a tiny root and shoot toward the surface. Successful sprouting confirms that planting conditions, including moisture and temperature, were appropriate. Knowing what a lettuce seedling looks like at each stage is important for the gardener to avoid accidentally removing desired plants while weeding.
The Emergence of Cotyledons
Lettuce seeds begin to sprout and emerge from the soil within 5 to 10 days, provided the soil temperature remains below 70°F. The first structure to appear above ground is a small, pale arch of stem called the hypocotyl, which straightens to pull the first leaves free of the soil. These initial structures are cotyledons, or seed leaves, which are structurally simple and typically rounded or oblong.
As a dicotyledonous plant, lettuce displays these first leaves in a pair, situated directly opposite each other on the stem. They are usually a uniform, light green color and have smooth edges, appearing plain in contrast to the mature plant. The cotyledons serve as the plant’s initial energy source, using stored reserves from the seed to power the first phase of growth. This stage lasts approximately two to three weeks, during which the seedling relies on these structures before it becomes self-sufficient.
Identifying the First True Leaves
The transition begins when the first true leaves emerge from the center of the two cotyledons. These leaves are structurally distinct and mark the point where the seedling shifts its reliance from stored energy to active photosynthesis. Unlike the smooth, simple cotyledons, the true leaves are miniature versions of the mature lettuce leaf and display the specific characteristics of the variety planted.
For example, a Romaine lettuce seedling shows slightly upright leaves, while a Butterhead variety might display a more ruffled texture. These true leaves appear slightly darker green and may have edges that are lobed, ruffled, or toothed. The appearance of the true leaves confirms the plant’s identity. The original cotyledons will eventually yellow and fall off once the true leaves are large enough to sustain the plant.
Distinguishing Lettuce Seedlings from Common Weeds
The uniformity and specific structure of the lettuce seedling help differentiate it from unwanted sprouts. Lettuce is a dicot, meaning it starts with two symmetrical, opposite cotyledons. This trait separates it from common grass weeds, which start with only one vertical leaf. Additionally, cultivated lettuce emerges in predictable lines, whereas many weeds have irregular spacing or pop up outside of a designated planting row.
A closer inspection of the stem and leaf texture provides clues for identification. Lettuce seedlings have smooth, hairless stems and leaves, especially in the cotyledon stage. Conversely, many common weed seedlings display small hairs or fuzz on their stems or leaf surfaces. Waiting for the second set of true leaves, with their recognizable lobed or ruffled texture, is the most certain way to confirm the plant’s identity before weeding.