Carrots are ready to harvest about 90 days after seeding but they do continue to grow larger. Harvest when the roots are of good size, but still tender. Carrots may be stored in the ground during cool winter months, unless freezes are expected. If frosts are predicted, dig up and store the carrots. If carrots are left too long in the soil or allowed to overmature, the roots become tough, woody, and may crack.