How to regrow vegetables from kitchen scraps

A jar of water on the windowsill with a spring onion root in it is not going to replace your grocery shop — but it might grow enough fresh green tops for a week of cooking. Approach regrowing with that expectation and it becomes a genuinely useful habit rather than a disappointment.

What regrows well from scraps

Some kitchen scraps regrow reliably and usefully; others are more of an experiment. Here's an honest rundown:

High-value, easy regrows:

• Spring onions (scallions) and leeks: the best scrap regrow, full stop. Place the root end in a shallow jar of water and new green shoots appear within days. Trim and use the tops repeatedly. Move to soil for longer-lasting plants.
• Lettuce base: slice off the lower 3–4 cm of a lettuce head, place cut-side up in shallow water. New inner leaves appear within a week. The regrown leaves are softer and sometimes more bitter than the original, but perfectly usable.
• Celery base: same method as lettuce — stand the base in shallow water and it will produce small inner stalks and leaves, useful for soups and stocks even when the stalks are thin.
• Bok choy and similar Chinese greens: cut the base and place in water as above. Regrows quickly.
• Lemongrass: place a stalk in water and it will root, then grow new leaves. Move to a warm, sunny pot for a proper lemongrass plant.
• Garlic greens: place a sprouting garlic clove in a small pot of soil or a jar of water. The green shoots that emerge are milder than a clove and work well chopped into dishes. You won't get a new bulb from this — just greens.
• Fresh herbs from cuttings (basil, mint, rosemary, sage): snip a 10–15 cm stem just below a leaf node. Remove lower leaves, place in water, and roots appear in 1–3 weeks. Pot up into compost once roots are 2–3 cm long.
• Ginger: plant a piece of fresh ginger rhizome (the knobbly root) with a growth bud visible, just below the surface of damp compost in a warm, humid spot. New shoots appear and, given time and warmth, you can harvest more ginger — though it's a slow, tropical-leaning plant that prefers warmth.
• Potatoes from sprouted tubers: a potato that has been left to sprout is not wasted — it's ready to plant. Cut into sections, each with at least one sprout (eye), allow the cut surfaces to dry for a day, then plant in compost or a potato bag. You'll get a proper harvest of new potatoes.

Worth knowing about:

• Carrot tops: place a carrot top (the very top with the leaf base attached) in shallow water. It will produce feathery green leaves — attractive and edible in small amounts as a herb — but will not form a new carrot root. That's not how carrots work — the root only forms from seed.
• Onion bases: will regrow green shoots in water, usable as a chive substitute. Planting in soil gives more sustained growth.
• Pineapple top: a fun project, but it takes 18–24 months to produce fruit even in ideal conditions, and needs a warm, bright climate or a very warm greenhouse. A rewarding long experiment if you have the space and patience.

Water regrowing vs potting on

Water is a convenient first step — it lets you see roots forming, it's visual and satisfying, and it requires no equipment beyond a jar. However, water alone lacks the nutrients and physical support plants need for sustained growth. Most water regrows will slow, stop growing and eventually decline if left in water indefinitely.

The productive approach is to treat water as a rooting stage. Once your cutting has developed visible roots (typically 1–3 weeks depending on the plant), move it into a pot of peat-free compost. From there it will grow as a proper plant, producing a much larger and longer-lasting harvest. Our guide to growing food in small spaces has practical ideas for small containers, pots and windowsill setups.

Step-by-step: spring onions and lettuce base

Spring onions:

1. Cut the spring onion about 3–4 cm from the root end, leaving the small white base and root attached. Use the green tops in your cooking.
2. Stand the root end upright in a small jar or glass with just enough water to cover the roots — roughly 2–3 cm. The white base should sit above the waterline.
3. Place on a bright windowsill (not in direct scorching sun) and change the water every 1–2 days.
4. Within 3–5 days, green shoots will emerge. You can snip and use the tops once they reach 10 cm or so, leaving the base to keep growing. One root end can be harvested from several times.
5. For longer production, transfer the rooted base into a small pot of compost. It will continue growing for several weeks or months, producing a succession of green tops.

Lettuce base:

1. Slice off the bottom 3–4 cm of a lettuce head, keeping the core intact. Use the leaves you've removed.
2. Place the base cut-side up in a shallow dish with about 1 cm of water — enough to reach the base but not to cover it.
3. Set on a bright windowsill and refresh the water every couple of days, keeping the level consistent.
4. Within 7–10 days, small new leaves will appear from the centre. Once you have a few centimetres of new growth, the lettuce base can be moved to a pot of compost for better results.

Realistic expectations

The internet is full of impressive regrow photos. Here's the honest version of what to expect from each type:

• Spring onions: excellent. One bunch of roots on a windowsill can supply green tops for 3–4 weeks. Moving to compost extends this to months.
• Lettuce base: a useful second harvest of softer inner leaves. Won't form a full new head — more like a bonus of salad greens over a couple of weeks.
• Celery base: produces leaves and very thin inner stalks good for flavouring. Don't expect full celery sticks — move to soil for anything close to that.
• Herb cuttings: genuinely great value. A few sprigs of basil or mint rooted and potted up become proper plants that produce herbs for months. This is one of the best regrow techniques full stop.
• Ginger: works well but needs patience — it's a slow-growing tropical plant. Keep it warm (above 18°C / 65°F), humid and bright.
• Potatoes: among the most productive regrows — one sprouted potato in a pot or bag gives a real harvest of new potatoes. Worth doing whenever you find a forgotten sprouted potato.
• Carrot tops: give feathery greens, which you can use in small amounts as a herb or garnish. Do not expect a new carrot.

Hygiene and avoiding rot

The main failure mode in water regrowing is rot. These steps minimise it:

• Change the water regularly — every one to two days is ideal, or at least every two to three days. Stagnant water quickly grows bacteria that rot the cutting.
• Use just enough water to cover the roots or the very base. Submerging the cut stem or the whole base promotes rot.
• Use a clean container. Rinse the jar when you change the water. A quick wash with washing-up liquid every few days helps.
• Remove any rotting material promptly. If a leaf base or outer layer softens and goes slimy, peel it off before it spreads.
• Avoid very hot, stuffy spots. Warm water encourages bacterial growth. A bright windowsill that doesn't overheat is ideal.
• Move to soil promptly once roots form. The longer a cutting stays in water, the greater the rot risk.

Moving successful regrows to soil

Once your regrow has developed visible roots — usually white and a few centimetres long — it's ready to move to compost. Choose a container appropriate to the plant: spring onions need only a small 10 cm pot each; a proper celery or lemongrass plant needs at least a 20–25 cm pot. Use peat-free multipurpose compost and ensure the container has drainage holes.

Water the compost before planting, then make a small hole with your finger and settle the rooted cutting in. Water gently — don't drench — and keep the pot on a bright windowsill or outside in a sheltered, sunny spot once it's established. A weekly liquid feed (dilute tomato feed or general-purpose liquid fertiliser) will help once the plant is actively growing.

For more ideas on growing food in limited space with containers, see our guide to growing food in small spaces.

Easy regrows at a glance

• Spring onion roots — snip tops, keep root in water, use green shoots in days.
• Leek root end — same method as spring onions.
• Lettuce base — shallow water, new inner leaves within a week.
• Celery base — shallow water, produces leaves and small inner stalks.
• Bok choy base — regrows quickly in shallow water.
• Herb cuttings (basil, mint, rosemary) — root in water, pot up in compost.
• Lemongrass stalk — root in water, pot up in warm, sunny spot.
• Garlic clove — pot in soil for mild garlic greens.
• Ginger rhizome piece — plant in warm, moist compost for new shoots.
• Sprouted potato — plant in compost or potato bag for a proper tuber harvest.