When you bought some vegetables from supermarket, for some vegetables, you ate mostly, and left a part of the plant, you can grow them in your garden or even in pots. without seeds or roots. They can grow faster than grow from seeds, and zero cost. You can even save the money buying seeds. In this video, I will show you how to grow them :
1.Pok Choy: 0:37
2. Celery: 02:30
3. Water Spinach: 03:46
4. Ceylon Spinach: 04:53
5. Sweet potato: 06:15
6. Potato：08:49
7. Garlic: 10:06
8. Onion: 13:05
9. Spring Onion: 14:37
10. Many herbs, such as basil, rosemary, mint, peppermint :15:41

Beyond that, there are more vegetable plants can be grown in your garden without seeds, such as ginger, Chinese yam etc.

Links related this video:
How to cutting propagate water spinach:    • 【种植24】空心菜种植的好方法----扦插空心菜/通菜，简单，超市买菜插几...