1. Green Onion
The next time you buy a bunch of green onions, keep the bulb end after you’ve used all the stalks. Plant the bulbs in a pot or container garden so that the top of the stalk pokes out of the dirt.
Green onions grow quickly, and within a couple days you’ll see new green shoots. Once they’re about six inches long, you can simply trim the shoots as needed and leave the bulbs in the ground. They’ll keep producing green onion stalks over and over!

2. Kale
Unless you already have kale planted, you’ll need to start with seeds or a small planter. However, once your kale is in the ground it will keep producing leaves for months and months!

Once your kale plants are mature, clip off leaves as needed, starting with the larger leaves at the bottom of the stem. As long as you leave a handful of leaves attached near the top, your kale will keep making new ones!

3. Leeks
Regrowing leeks works just like regrowing green onions. Save bulbs with at least an inch or two of the stalk. Plant the bulbs in the ground with the stalk peeking out and they will regrow!

4. Basil
The next time you purchase fresh basil or visit a pho restaurant, save a sprig of basil! Cut the stem, keeping a few leaves  attached. Place in a jar of water to generate roots, then you can move to a planter.
When you get the pretty little plant home, divide it up into 10-12 cuttings and place them in small containers filled with fresh water. Basil roots very easily and your kitchen windowsill is the perfect place to start a little “basil nursery”.

• Begin this rooting process no more than 3-4 weeks before it’s safe to plant basil in your climate zone, which is usually when temperatures will consistently remain above 50˚ at night, the days are warm and sunny and there’s no danger of frost.
• A healthy basil plant will produce anywhere from 10-12 plantlings, maybe more. If you have limited space and/or can’t use that much basil, go ahead and root them anyway – the little plantlings will make great gifts for your “foodie” friends – believe me, they’ll be thinking quite fondly of you each time they snip, snip, snip!
• The best place to root basil indoors is a bright but not intensely hot window. Morning sun is great but a lot of intense afternoon sun will be too much for the little cuttings.
• The cuttings may look a bit droopy, a day or so after you divide them. They are just adjusting to a new environment; keep the water level full and be sure to change the water every other day.
• Try to use water right around room temperature when changing out the water. this will help avoid shock.
• If it’s going to be below 40˚F at night, remove your “babies” to the counter until morning, then return them to the windowsill.
• Don’t be snitching basil during this growing period. That’s a good way to put them into irreversible shock. I’m telling you this from personal experience.
• I like to use a container that will hold at least a cup of water and have a fairly wide opening at the top. I’ve found that the little plantlings don’t do well in containers that are too small or that have super narrow openings.
• A little warning: sometimes a few of the “little offspring” just don’t make it – it’s too shocking for their system. You should have plenty of others that flourish so just discard the ones that fail.
• Once you plant your new little herb family, they will need plenty of water, especially in the hot summer months. They will wilt, droop and their growth will be stunted if they don’t receive enough moisture.

How to Root Basil from Cuttings

Materials:
1 large full, healthy basil plant, preferably planted in soil vs hydroponic
kitchen scissors or a sharp knife
small glass containers
fresh tap water

Instructions:

• With a scissors or a sharp knife, cut 3-4 inch long cuttings (they may end up being a bit longer depending on where the first leaf node is) right below a leaf node; this is where a leaf joins the main stem. Although your little cuttings will eventually sprout roots all the way up the stem, the leaf node is generally where the new shoots will begin.
• Remove leaves from cuttings on the lower 2 inches. (I place any basil leaves that are left over in a small plastic storage container and store them in the refrigerator till I need them for cooking.)
• If there are tiny leaves at the leaf node, don’t worry about these, they can stay on.
• Place cuttings in small glass containers of water on a bright windowsill. Choose an area that gets lots of light, but not direct sun, as the little plants could go into shock at this point with hot sunshine. You can put 4-6 cuttings in each glass. The cuttings might wilt a little at first and you may lose a few, that's normal. You should have plenty that survive.
• Watch the water levels carefully, adding water to keep stems immersed. Change the water every other day to keep it fresh. (Be sure it's not too cold on your window sill. Basil loves warmth and doesn't do well if it gets a chill.)
• After 5-7 days you will begin to see some tiny white roots forming. Every day more and more will appear. Let the roots grow to about 2 inches. Continue to change the water every other day. The process will take 12 days to 18 days, from start to finish.
• You are now ready to plant your plants outdoors in a sunny spot with good drainage.  Keep the plants protected from intense sun for a week or so until they get established. Once they adjust, the little plants will start growing new leaves and shoots. Before you know it, you'll have an abundance of fresh basil!

tips on growing and replanting source: How to Root Basil from Cuttings | The Café Sucre Farine

5. Garlic
To regrow garlic, you can start with individual cloves or a whole head of garlic. Simply bury the cloves under about an inch of soil and keep watered.

The garlic is ready to harvest when it starts to turn yellow.

6. Potatoes
When potatoes start to sprout, they’re no longer good to eat. But why throw them away when you can use them to grow more potatoes…for free!

To regrow potatoes, cut a sprouting potato into chunks, so that each chunk has an eye and a sprout. Plant with the eye facing up and cover with a few inches of dirt.

Keep watered and in a few weeks those potato pieces will start to sprout and grow full sized potatoes!

7. Romaine Lettuce
When you cut the leaves off a head of romaine lettuce, keep the end! You can plant this in soil, water, and it will start to regrow leaves.

Similar to kale, you can clip the leaves as needed and your romaine plant will grow more!

8. Bok Choy
Bok Choy can be regrown just like romaine lettuce!

9. Celery
Celery can be regrown by saving the base and placing in a cup of water until leaves sprout. At that point, you can transfer the celery plant to a pot with soil.

In a few weeks the stalks will grow taller and thicker and soon be ready to enjoy!

10. Cilantro
Like basil, cilantro can be regrown from cuttings, though not quite as easily. However, once you have a mature cilantro plant, you can cut leaves as needed and it will keep on growing!

11. Rosemary
Rosemary can be regrown by cutting a 3″ piece from a mature plant. Strip the leaves from the bottom half of the cutting and plant that end in soil.

It’s recommended to start in a small planter, keeping the cuttings moist and with indirect sunlight, until they begin to take root and grow. At that point you can transplant to their final location.

12. Onion
he next time you cook with  onions, save the bottom piece of the onion that contains the roots! This one piece of onion can be sprouted and used to re-grow two or more onions!

To grow a full-sized onion bulb can take 3-4 months. Or you can clip the greenery from the onion and use that!

13. Sweet Potato
Sweet potatoes are grown a little differently than regular potatoes. Instead of planting the potato itself, to regrow sweet potatoes you plant the sprouts, also known as “slips.”

You can start with a sprouting sweet potato like this one:

Or you can purposely sprout your own. Place it in a jar of water to grow the slips. Once they’re about 5 inches long, twist the slips and pull them out of the potato. Now you can plant the slips in the dirt – about halfway deep.

The really cool thing is that you can keep growing countless slips from one single potato!

14. Ginger
Regrowing ginger from scraps is easy and your ginger root will continue producing as long as you take care of it!

Simply plant a piece of ginger root in a pot with soil, water, and wait for it to sprout. After a few weeks, your ginger root will grow so that you can begin harvesting small pieces as needed.

When you’d like to get a piece of ginger, push the dirt away until the root is visible, cut a piece off, and leave the rest planted. Recover any cut area with dirt so it can regrow.

15. Mint
Mint is a fairly easy plant to grow and spreads quickly on its own. However, you can regrow mint cuttings as you would basil and start new plants as needed.

You can also take fresh mint cuttings from the grocery store and grow roots in water, then plant in soil.