Can You Grow Onions from Supermarket Bulbs?

Why Planting Whole Onions Doesn't Work

Planting mature onions from the grocery store yields only green tops—not new bulbs. Here's why and what to do instead.

The Biology

Onions are biennials. The bulb you buy is a mature, second-year storage organ. When replanted, it tries to complete its life cycle by sending up a flower stalk (bolting), not by forming a new bulb. The hollow green stalks are simply the plant using stored energy to reproduce via seed.

What You'll Get

• Edible green tops (use like scallions/green onions)
• Eventual flower stalk and seed head
• No new onion bulb formation
• Original bulb will soften and rot

Proper Onion Starting Methods

For actual onion bulbs, start with:

• Seeds: Started indoors 8–10 weeks before last frost
• Transplants: Young plants from nurseries in spring
• Sets: Small, immature bulbs (most common for home gardeners)

Using Your Sprouted Onions

Don't discard them! Harvest the green tops as needed for cooking—they're perfectly edible and have a mild onion flavor. Once the bulb exhausts itself, compost it and start fresh with proper onion sets or plants next season.

Save supermarket onions for eating, and source your planting stock from garden centers or seed catalogs for a real harvest.