I put the white root end of a green onion in a glass of water on my windowsill, mostly as an experiment. Three days later, a new green shoot was visibly taller. A week later, I had a full green onion again. I cut what I needed and left the root in the water. It grew back again. And again. I have not bought green onions in six months.

Some vegetables will regrow from scraps indefinitely with nothing more than water and sunlight. Here are the easiest ones — and the ones that are not worth the effort.

The Easiest: Green Onions and Leeks

This is the gateway drug of kitchen scrap gardening. Put the white root end in a glass with an inch of water. Place it on a sunny windowsill. Change the water every two or three days. You will have usable greens within a week. Snip what you need from the top — the base keeps growing. Eventually it will slow down after four or five harvests. At that point, plant it in soil or start a new one.

Leeks work the exact same way. Celery too — though celery regrows as leaves and thin stalks, not a full head. Good for flavoring soups, not for snacking.

Surprisingly Easy: Lettuce and Bok Choy

Save the bottom two inches of a head of romaine or bok choy. Place it in a shallow dish with about half an inch of water. Within a few days, new leaves will sprout from the center. After a week, transfer to soil if you want it to grow to full size. In water alone, it will produce enough leaves for a small salad or a sandwich topping before running out of steam.

Worth Trying: Ginger and Garlic

A piece of ginger root with a small bump (an “eye”) will sprout if planted in soil. One grocery store ginger root can turn into a potted plant that produces fresh ginger for months. It takes longer — a few weeks to sprout, months to harvest — but ginger is expensive and homegrown is noticeably more aromatic.

Garlic: plant a single unpeeled clove in soil, pointy side up. It will grow green shoots you can snip like chives, and eventually produce a full head of garlic underground. Takes six to eight months. Low maintenance, just slow.

Not Worth the Effort: Carrots and Potatoes

Carrot tops regrow into leafy greens — but not a new carrot root. The greens are edible (pesto, garnish) but most people do not bother. Potatoes will sprout and grow into plants, but they need a large container or garden bed and take months. If you have outdoor space and patience, go for it. If you are looking for quick windowsill wins, stick to green onions.

My windowsill now has a rotation of green onions and a small pot of ginger. It is not going to replace grocery shopping, but it is free food that takes zero effort, and it feels like a tiny magic trick every time I trim some greens for dinner.