I recorded this tutorial video showing how you can regrow more fennel from an existing plant.
When you buy fennel from the store or grow some in your garden, the bottom of the bulb has a base where the roots grew from. When you cut up your fennel plant to use for cooking, leave this base and a little bit of the attached bulb intact, this is the piece a new plant will start growing from.
Watch my video below for more detailed info.
Put the little base piece you saved in a shallow dish with water. Place this on a sunny windowsill and change the water every couple of days so it does not rot nor get moldy. After 3 to 5 days you should start seeing new growth from the base and eventually you should also see new roots growing in the water. After there is a good amount of roots you can plant the fennel in a container with soil or directly in your garden.
Good luck growing your veggies!
Thanks for checking out my post!