How to Plant a Sprouted Onion? Step-by-Step

Louise

Written By, Louise

Updated on 22 Sept., 2025

8 min read

How To Plant A Sprouted Onion
AI Generated Image: Southern Reside

Discovering sprouted onions in your pantry doesn’t mean you have to throw them away. These seemingly unusable vegetables present an excellent opportunity to grow fresh, homegrown onions with minimal effort and cost.

Gardeners have many options for growing onions; however, using sprouted onions from your own kitchen adds a sustainable touch to the process. This blog will walk you through the process of planting a sprouted onion!

Why Do Onions Sprout?

When an onion becomes over-ripe, the outer skin develops a thicker texture and green shoots begin to sprout from the top. Since onions are bulb plants, they reproduce by dividing into multiple bulbs, much like garlic. Just as planting one clove of garlic yields a complete head of cloves in the fall, the following year, sprouted onions are ready to divide and multiply when the green shoots appear.

Sprouting begins when the onion is exposed to perfect growing conditions, and it does not necessarily require soil contact to initiate this process. When stored in warm, humid, or light-filled environments, onions are essentially tricked into believing spring has arrived, prompting them to begin the sprouting process.

Where to Plant an Onion Sprout?

While planting an onion sprout, it is important to consider the location. Onions are sun-loving plants and require at least 12 hours of direct sunlight daily to thrive. So choose a spot in your yard where it gets sunlight, preferably one that receives consistent light throughout the day. When it comes to soil requirements, they grow best in fertilized, well-drained, slightly acidic soil.

How to Plant Sprouted Onions?

Planting Sprouted Onion in the Garden
AI Generated Image: Southern Reside

Here is a simple way to get started with planting sprouted onions at home:

  • The first step is to carefully cut the sprouted onion lengthwise to expose the center sprouts. This cut should be made with precision to avoid damaging the root of the onion.

  • Once the onion is cut, the outer layers must be peeled until only the center cluster of sprouts remains. These sprouts are sometimes stuck together, but should be carefully separated into individual plants.

  • If the outer layer remains firm, it can still be used for cooking. If they are soft, discard them or add them to the compost pile.

  • Before planting directly into soil, keep the separated sprouts in water for better root development. Put each sprout in a bowl of water until new roots begin to form.

  • Once the roots pop out, the onion can be planted into the ground or a container of potting soil with the root end down. It is better to separate the sprouts before planting. Planting too close to each other can lead to mold development beneath the soil.

How Deep to Plant an Onion Sprout?

Plant the seedlings just 1 inch deep into the soil, as onions do not require deep planting. Space each sprout at least 4 inches apart, to ensure that the bulbs have enough room to expand without crowding. Once planted, it can take up to three weeks for onion sprouts to look perky.

How Long Does It Take to Harvest?

It takes around four months for sprouted onions to be ready for harvest. For instance, if sprouted onions are planted in late February, they can be harvested by mid-June. As flower buds begin to appear around May, it is advisable to remove them before they open.

Whether the onions come from the grocery store or from the garden, trimming the blooms can improve the size and quality of the final harvest. Once the buds are removed, the bulbs usually continue to develop quickly.

How to Care for Onion Plants?

It is important to continue watering and weeding around onion plants consistently throughout their growth. Using fertilizers can help in their healthy development. It is advisable to water onion plants in cycles rather than every day. Overwatering should be avoided, as excess moisture can lead to bulb rot.

Gardeners can choose between organic options such as compost or manure, or use store-bought fertilizers to replenish nutrients in the soil. Providing balanced nourishment ensures that the onions grow to their full size and flavor potential.

When is the Best Time to Plant?

Onion Planted in the Garden
AI Generated Image: Southern Reside

Onions are a cold-hardy crop that can often be planted before the final frost. They grow best in temperatures between 50–75°F but can tolerate conditions as low as 20°F, depending on the variety.

Typically, onion sprouts can be planted 4 to 6 weeks before the last expected frost, as long as the soil is workable. For gardeners in regions with short growing seasons or late-thawing soil, starting onions indoors in a small container is a practical alternative. Once conditions improve, the seedlings can be transplanted outdoors.

Conclusion

Planting sprouted onions is a simple and cost-effective way to reduce waste and grow fresh produce at home. With the right care, proper sunlight, right spacing, and balanced watering, these kitchen scraps can develop into healthy bulbs. It’s an easy and satisfying project for any home gardener.

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