Fennel can be propagated from seed, cuttings, or from the base of a bulb

From seed 

  1. Sow seeds in the garden in early spring after the last frost.
  2. Cover seeds with 1/4 inch of soil.
  3. Space seedlings 10–12 inches apart in rows 18–24 inches apart.
  4. Water frequently after shoots appear.
  5. Protect the bulb from the sun by hilling soil around it once it begins to develop.

From cuttings 

  1. Choose a healthy stem.
  2. Make a clean cut with sterilized scissors.
  3. Remove lower leaves to prevent rot.
  4. Apply rooting hormone.
  5. Create a hole in the soil with a pencil.
  6. Insert the cutting and gently firm the soil.
  7. Cover with a plastic bag to maintain humidity.
  8. Place in a sheltered spot with indirect light.
  9. Water consistently, but avoid waterlogging.

From the bulb 

  1. When cutting up fennel for cooking, leave the base and a small amount of the attached bulb intact.
  2. Place the base in a shallow dish, glass, or jar of water with the base facing down.
  3. Place the dish on a sunny windowsill.
  4. Change the water every couple of days.
  5. After a little more time, new roots should start to sprout.