Right before we transplanted our seedlings the other day, we noticed that a new leaf had appeared on several of our zucchini plants. It had started out with two small round leaves, and suddenly a tiny, more jagged leaf was poking out:
WOW! Where did the little leaf come from? Isn't it beautiful?
Well, what we see poking out is the zucchini plant's first 'true leaf'. When a seed first emerges from the soil, it has a set of two leaves called cotyledons (the beautiful round leaves that we watched unfurl from each of our baby plants). The cotyledons are actually a part of the seed, and act as a food source for the sprouting seedling. At this time the seedling does not conduct photosynthesis. It gets all its food and nutrition from the cotyledons.
As the seedling becomes stronger and healthier, it will begin to form two more leaves that look very different from the cotyledons. The true leaves will look more like what the plant’s leaves look like when mature. Once the true leaves are present, the plant is now actively photosynthesizing. Eventually the cotyledons will wither and fall off as the true leaves take over the job of feeding the plant.
What an exciting milestone! Our baby plants are one step closer to actually producing vegetables!