Cotyledon leaves are the first to appear on a cannabis or other plant embryo. Also known as seed leaves, cannabis cotyledon leaves grow in pairs, although other plants may have one or three cotyledon leaves. As the plant matures, the leaves will fall off to make room for the other parts of the plant to continue growing.
What is the function of the cotyledon?
Seed-bearing plants typically have cotyledons and they are the first leaves to appear when a seed germinates. The cotyledon leaves help break open the seed coat so that the seed can sprout. Cotyledon leaves also play the vital function of providing the seedling with the nutrients and energy it needs to begin the growing process.
When flowering plants like cannabis germinate, the cotyledons emerge and pop up out of the growing medium before anything else. These embryonic leaves store food and nutrients and help direct energy and food reserves to the parts of the germinating seed that need it most.
Shortly after the cotyledon emerges, the growing plant will push a stem up through the center of the seed leaf, after which the first set of "true leaves" will appear. Through this process, cotyledon leaves essentially help jumpstart the process of photosynthesis, which the true leaves then take over as the plant continues to grow.
When the young cannabis plant has enough true leaves producing food through photosynthesis, the baby plant does not need to absorb stored food and energy from the cotyledons. No longer required to keep the plant alive, the cotyledons will naturally wither, turn yellow, then brown. At that point, most cotyledons simply fall off by themselves.
What do healthy cotyledon leaves look like on cannabis plants?
Cotyledon leaves do not look like regular cannabis leaves. That's why people will often call a cotyledon a seed leaf or a first leaf, while the first regular-looking leaves are called true leaves. Instead of the famous, multi-fingered, serrated leaf that cannabis is known for, cotyledon leaves are more rounded.
When you see true cannabis leaves begin to grow above the cotyledon leaves, that's a sign that your seedling is well on its way to becoming a strong, healthy plant. Cannabis plants typically produce two cotyledons, although sometimes there may be three or even four cotyledon leaves present on a young plant.
Do you need to prune cotyledon leaves?
You do not need to prune cotyledon leaves. They will typically fall off all on their own. If you have a plant with a brown and withered cotyledon leaf that hasn't fallen off, and the plant is healthy with a lot of true leaves, you can go ahead and pluck it off. When your plant is still germinating and growing its first stem and true leaves, do not mess with cotyledon leaves as they are helping to fuel the young plant until it can keep itself alive.
Why is it called a seed leaf?
A cotyledon leaf is often referred to as a seed leaf because cotyledon leaves are not true leaves, in the sense that these leaves are not designed to keep the plant alive throughout its life cycle. Instead, they help the seed absorb food so that the growing embryo can advance from a germinated seed to a sprout to finally having enough leaves to feed itself and keep itself growing until it is ready to flower.