Glossary

Seed leaves (cotyledons) are the first leaves a plant develops after germination. They are already present within the seed kernel, as part of the plant embryo. After emerging they supply the seedling with energy, either from their store of nutrients or via photosynthesis as soon as they reach the light.

What are seed leaves?

Seed leaves are clearly different from the true leaves that appear later. Generally they are simpler in structure – they’re there to nourish the seedling in its first phase of life. As soon as the plant forms its own true leaves the seed leaves lose their function and generally die away. 

Monocots and dicots – one seed leaf or two?

Plants fall into two groups depending on whether they have one cotyledon (monocots) or two (dicots):

• Monocots (or monocotyledons) have one seed leaf – examples include cereals and leeks.
• Dicots (dicotyledons) form two seed leaves – plants including tomatoes, squashes and beans.

This distinction is also apparent in other plant features like root formation and leaf structure.

What it means for gardeners

Seed leaves help you identify particular plants at an early stage. Especially when you’re starting vegetables and herbs it’s helpful to be able to recognise their typical seed leaves – this will help you identify weeds quickly, too! 

• Already present within the seed 
• Feature that helps you identify seedlings 
• Key development stage when starting plants from seed