Sowing: Start Florence fennel seeds indoors about a month before the last frost, planting them in peat pots 1/4" deep; keep the temperature around 65-75 degrees F for best germination. Fennel can also be direct sown as soon as the soil temperature reaches 65 degrees F. Space the seedlings or seeds about 12" apart in fertile, well drained soil and full sun. Transplant the seedlings carefully, since shock may cause them to bolt. Fennel must be planted away from other garden plants, since it tends to have a negative effect on their growth.