What happens under the soil while you wait?

It’s easy to be impatient while waiting for seeds to germinate, but it doesn’t help. Pepper seeds can take as little as 10 days and some varieties can take as long 120 days to germinate. Thankfully most common vegetables and flowers will germinate in 2 to 3 weeks. So what happens in the soil after you plant your seed? What goes on down there? Well, there are three phases of germination: the water uptake (hydration), the activation of processes and growth. To show how this process works we can follow a single chard seed from germination to seedling.

This is an MRI I took of a dormant chard seed. You can see the white C-shaped embryo with its cotyledon on the right

Before you put your seed into the ground it was most likely dormant, sort of like hibernation for seeds. This means that it was dehydrated and waiting for suitable environmental conditions before it would germinate. These conditions, warm air and soil temperatures, sunlight and rain, are provided by you when you plant. When you first plant your seed, it takes up water, loosening its seed coat (the outer hull around your seed) and allowing the tissues to swell and expand. This is the hydration phase. The seed coat protects the seed from microbes and other things that could potentially eat or destroy it. The expanding tissue will be the food source for your emerging plant. If the seed coat wasn’t loosened the tissues couldn’t take up water and expand, this is why some seeds need to have their seed coats nicked (like Lotus) to improve germination. 

The next phase of this process is the activation. This is when the seed’s metabolism starts. All that hydration starts moving nutrients and energy stored in the seed so the embryo can begin the final stage: growth. First the tiny root will emerge and start to grow, and the shoots will follow a couple days later. 

Germinating chard seed. You can see the brown seed coat and the white root

With most seeds it doesn’t matter which direction you orient the seed. The roots always grow down and the emerging leaves will grow up a phenomenon called gravitropism. In the roots, there are tiny granules that fall downward so the roots can always detect which direction is down. The seed only has the food that was stored in it to keep it going. If seeds are planted too deep the shoots might not have enough energy to break the surface, if seeds are too shallow they might dry out or be baked by the sun. Planting seeds to the recommended depth ensures that your seeds will have room to germinate, but still be safely nestled in the soil. Once your shoots break the soil surface, the first two (or one) leaves that emerge and extend are called cotyledons. These aren’t actually true leaves, those will come later. 

Chard seedlings with their cotyledons

Baby chards who now have their true leaves

And that’s what happens, while you wait!