After you gain full control for the first time and have the tools such as Hoe and Watering Can, each time you have planted all (ten) Cabbage Seed in the field, go to left, to Lighthouse area, and talk to Jeanne to receive another ten Cabbage Seed. Go back to your field, and plant it. Then you can repeat this as much as you wanted. But, this can be done before you repair Sam house, a merchant who sell items in the town.