Cotyledon

Cotyledons serve as the seedling's initial energy source, providing the nutrients stored from the seed until the true leaves develop and photosynthesis takes over. Once the first set of true leaves (single-pointed cannabis leaves) emerges and begins absorbing light, the cotyledons gradually become less important. They typically yellow and drop off within the first few weeks of growth. The appearance of healthy, green cotyledons is a positive sign that germination was successful and the seedling has viable nutrient reserves.

Growers look at cotyledons as early health indicators. Cotyledons that emerge pale, deformed, or fail to open may indicate a weak seed, poor germination conditions, or genetic abnormalities. Healthy cotyledons are symmetrical, green, and open fully within hours of breaking the soil surface. Once a seedling develops its first two or three sets of true leaves and the cotyledons begin to yellow, the plant has transitioned from seed-stored nutrition to photosynthetic self-sufficiency. At this point, the seedling is considered established and ready for its normal growth phase.