There are a number of fruits and vegetables that can be replanted from kitchen scraps
Lettuce, Romaine Lettuce, Cabbage, Bok Choy are all relatively easy to grow from scraps. Instead of throwing out leftover lettuce, simply place them in a bowl with a small amount of water, so long as the crown of the plant remains intact, your lettuce will continue to regenerate new leaves all season long. Keep it there generating lettuce in ample sunlight and mist the leaves at least twice a week.
Celery is an easy food to grow from scraps. Cut off the base of your celery and place it in a bowl with with warm water . Keep the bowl in the sunlight and in about a week, you will begin to see the leaves thickening and growing out from the base. At this point you can transplant your celery in the soil and wait for it to grow.
Lemongrass can be difficult to find, but it's not that hard to regrow once you've found it. Lemongrass is grass and will grow just like regular grass. Simply place the leftover root in a glass bowl with enough water to cover it and place it in a sunlit area. In about a week, you'll notice new growth, when this happens you can transplant your lemongrass to a pot or your herb garden.
Bean Sprouts can be easily grown yourself as well. Soak the beans that you want to grow in a container with shallow water.
Leave them overnight, in the morning, drain off the water but leave the beans in the container. Cover the container with a towel or rag overnight and rinse them again in the morning. Repeat this on a daily basis until the sprouts begin to appear, and then until they reach the desired size . Nearly all beans can be re-sprouted, but this works best with smaller varieties such as mung beans, Adzuki beans, lentils. Larger varieties of beans will sometimes develop mold before they sprout.
Potatoes can be regrown from potato peelings or slips. Slips are potatoes cut into quarters. The slips or peelings must have eyes on them. Peelings should be cut into two inch pieces, be sure that there are 2 to 3 eyes on every piece. Allow them dry out overnight and then simply plant them about four inches deep in your garden soil. The eyes should be facing up when planting. It will take a few weeks before you see the potato plant begin to sprout up. Supermarket potatoes are frequently treated with a growth inhibitor to prevent sprouting while in storage. If you buy a potato from the store, be sure to find out if you're getting a bush or a vining type.
Sweet Potatoes can also be regrown much the same as regular potatoes. Cut the sweet potato in half or quarters depending on how large it is and suspend it using toothpicks above a container of shallow water. Roots and sprouts start to appear in just a few days. Once the sprouts reach about four inches in length, cut them off and place them in a container of water. When the roots from this container reach about an inch in length they can then be planted in the soil.
Beets, Turnips and Parsnips can also be grown from clippings and kitchen scraps. Save the tops and place in a container of water. New green tops will begin growing in just a few days. Allow the root to continue growing until your ready to transplant into the garden.
Avocadoes are another crop that is easily regrown. Thoroughly wash the seed and use toothpicks to suspend it over a bowl of water . The water should cover the bottom inch of the avocado seed. Keep it in a warm place away from direct sunlight and remember to replenish the water as it evaporates. It takes over a month for new growth to appear. Once the stem and roots do appear and the stem reaches about 6 inches you'll need to trim it back to 3 inches. When the leaves appear, you can plant the seed in soil, leaving about half of the avocado plant above ground.
Garlic is very easy to grow with just a single clove. Garlic comes in a bulb with several cloves grown together, pull off one and plant it with the roots facing down in potting soil. Place it in direct sunlight , Garlic is a cool season crop , so it best kept indoors to it becomes established. Once the new shoots are established, cut them back and your plant will produce a bulb. You can take a clove from this new bulb and repeat the process.
Ginger Root is another easily grown crop from scraps. Place a piece of your ginger root in potting soil with the buds facing up. In about a week you should notice new roots and shoots, once this occurs you can uproot it and do it again. Remember to save a piece of the underground stem [rhizome] so that you can continue to replant it and grow more.
Pineapples , yes, even if you don't live in the tropics you can grow your own pineapple. Cut the top off and insert a few toothpicks to suspend it above a container filled with water. Place the the container in a warm spot in direct sunlight. Change the water 2 - 3 times a week, keeping the container filled so that it reaches just the pineapple base. In about a week you will notice roots once they are fully formed you can transplant the pineapple into potting soil. Planting outdoors is not recommended unless of course you live in a tropical or sub tropical climate.
Onions - cut the root of the onion off and make sure that you leave about a half an inch of the onion top when you do this. Cover loosely with potting soil and keep it in a sunny area. For green onions and scallions cut the white base with the roots intact in a container of water and place in direct sunlight. Change the water 2 - 3 times weekly and it will continue to grow. Just snip what you need and allow it to continue growing.
Mushrooms are a little tricky, but they can be grown from cuttings. You will need a warm humid area and rich soil. Home Grown mushrooms fare better in a pot because you will have better control of the temperature and humidity. Cut away the mushroom head and plant the stalk or stem in the soil. Leave the top exposed and this base will grow into a new mushroom head.
Fennel can be grown much the same way as celery, but, the roots have to be kept intact. You'll need at least an inch of the fennel base for it to rejuvenate. Place the fennel base in a container with of water, leaving only the very top exposed to the air, and leave it in direct sunlight. When the roots grow become well established and strong you notice new green shoots coming up from the center of the base, you can then transplant it into soil.
Basil is very easy to regrow. You need a stem about four inches high. Place this stem in a glass of water leaving the leaves well above the water line. Leave the glass sitting in a sunlit area but not direct sunlight. Roots should begin to form within a few days. When those roots reach about 2 inches you can transplant into soil.
Cilantro can be grown from scraps as well, using the same process as with Basil.