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This Garden Vocabulary series seeks to introduce and explain to you — and in many cases, myself — words and terms associated with gardening. Please let me know if  there are any terms you would like me to explore. You can leave your ideas in the comments section and we can learn together!


A cotyledon (pron.: /kɒtɨˈliːdən/; “seed leaf” from Greek: κοτυληδών kotylēdōn, gen.: κοτυληδόνος kotylēdonos, from κοτύλη kotýlē “cup, bowl”), is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous (“monocots”). Plants with two embryonic leaves are termed dicotyledonous (“dicots”) and placed in the class Magnoliopsida.

Read the entire article on Wikipedia, Cotyledon

We are often instructed, when growing plants from seedlings, to thin or re-pot them when the first “true leaves” appear. Of course, it helps to understand exactly the difference between seed leaves (cotyledon) and real leaves. This Wikipedia article gives a good start, although it is a bit technical in nature and focuses on the the use of seed leaves for plant classification rather than how it might be used by the average gardener.

Seed leaves are part of the plant embryo, established after seed fertilization and used to start the plant growing. They use the food stores of the original seed to germinate and begin growing. For most garden plants, seed leaves appear as 2 leaves on the seedling whereas the first true leaves are often seen in a group of four leaves further along the stem than the seed leaves. In many cases, the seed leaves look distinctly different from the true leaves of whatever plant you are growing. You can see an example of this is the video below.

Further reading on Cotyledon (Seed Leaves):


Previously on Garden Vocabulary: