I bet you’ve heard the term ‘true leaves’ tossed around in the gardening community like common every day jargon. But if you’re new to gardening, the term may not be as obvious as experienced gardeners may think. Recognizing true leaves on your tiny seedlings and understanding what to do when they appear is critical to the success of your seed starting efforts.
The term true leaves seems to imply that some of the leaves on tiny seedlings are fake, which makes no sense as you watch your seedlings emerge from the soil full of life. Nothing fake about it. So to end further confusion, true leaves are simply the second set of leaves that develop on seedlings shortly after they push through the soil.
It’s fascinating to see something so magnificent emerge from such a tiny seed. But don’t stop paying attention after your seedlings pop through the soil. The real excitement is about to unfold!
The first set of leaves develop from the cotyledon as the seed germinates. The cotyledon is part of the embryo within the seed. The cotyledons are also referred to as ‘seed leaves’. The seed leaves can emerge anywhere from 3-14 days from the date the seeds were planted, depending on the seed type. The seed leaves are important because they provide the initial source of energy for the seedling before it starts to produce energy via the photosynthesis.
When true leaves develop, they begin as a tiny bud at the junction between the two cotyledons. Zoom in and you’ll see it forming. It typically takes a few days for the buds to unfold and spread out into tiny leaves.
It can take a while for the true leaves to appear, but once they do, the next sets of leaves seem to follow quickly thereafter. You’ll also notice that true leaves look quite different from the seed leaves in that they resemble the leave structure of the mature plant.
When I see the true leaves are well formed, that’s my cue to transplant seedlings from seed starting trays to their second container. I like to use 4” pots for the second container and label these transplants as ‘T1” to indicate first transplant.
Keep an eye on your seeds every day. Capture a shot when the true leaves appear and make a note of the date in your garden notes. Remember different plants develop true leaves at different rates, so don’t be alarmed if all your seeds do not develop true leaves at the same time, even if they were sown on the same date!