How to Grow Multiplier Onion Bulbs: Potato Onion Planting

Multiplier onions are a distinctive type of onion that produces clusters of bulbs from a single planted bulb, similar to shallots but larger. They can be grown as a perennial food crop by saving and replanting a portion of the harvested bulbs each season.

Multiplier onions are productive and easy to grow. They are valued for their excellent storage life, dependable yields, and versatility in the kitchen. Their mild, sweet flavor makes them ideal to eat fresh, roast, sauté, or use in soups. 

You’re missing out if you don’t grow multiplier onion bulbs in your garden!

Multiplying Onion Sets For Sale

Our Fall Planted Bulbs Collection is available to purchase each year around the beginning of September, and they ship out right on time for fall planting! You can join the waitlist any time of year to be among the first to know when it launches. 

Use the MIgardener Fall Bulb Planting Guide to walk you through the magic of growing bulbs planted in the fall. This free resource has all the information you need! It covers how to grow garlic, how to grow shallots, Egyptian walking onions, potato onions, and ornamental flowering favorites.

What Are Potato Onions

Onion crops come in many different types and flavors, from sweet onions to shallots to bunching onions to red onions. Now you can add another to the list that you may not have heard of: the potato onion!

Potato onions are a unique type of heirloom multiplier onion that produces clusters of flavorful bulbs from a single planted bulb—much like potatoes do, hence their name! They are so easy to grow and highly productive. Here are some potato onion traits:

• Type: Multiplier onion

• Bulbs per Cluster: approximately 6-12 bulbs

• Flavor Profile: Mild to moderately pungent with a rich, sweet onion flavor that becomes even sweeter when cooked

• Storage Life: 6-12 months

Potato onions are commonly confused with Egyptian walking onions, but there are distinct differences: 

• Potato onions multiply underground in clusters, while Egyptian onions also produce small bulbils at the top of their stalks that bend over to the ground and root themselves, resulting in new onion plants. 

• Potato onions are grown primarily for their underground bulbs, while Egyptian onions are harvested for their greens, top bulbils, and underground bulbs. 

• Potato onions have a mild, sweet onion flavor, while Egyptian onions tend to have a stronger flavor. 

• Potato onions remain where planted, while Egyptian onions can “walk” through the garden as their top bulbils fall and root. 

When to Plant Multiplier Onion Bulbs

If you live in a cold climate, plant your multiplier onions in the fall about 4–6 weeks before the ground freezes. This will allow the roots to get established before winter. 

If you garden in a warm southern climate, plant multiplier onion bulbs during the coolest part of the growing season, in the late fall through winter.

How to Grow Multiplier Onions (Potato Onions)

Follow these simple step-by-step instructions to plant potato onions or other multiplier onion bulbs:

1. Sunlight - Give onions full sun, which means 6–8+ hours daily. 

2. Amend the Soil - Plant multiplier onions in loose, well-draining, fertile soil. Pro-Tip: Amend your soil with finished compost to improve fertility and drainage. I recommend reading How to Improve Soil Drainage if you have compacted or clay soil.

3. Soil pH - Multiplier onions like a soil pH of 6.0 to 6.8. 

4. Fertilizing - Apply MIgardener’s Bulb+ Fertilizer at the time of planting and again in early spring when active growth begins. Bulb+ is formulated with the organic sulfur and phosphorus that bulbs and tubers need to encourage strong root development and protect them from rot and mold!

5. Plant Spacing - Plant multiplier onion bulbs 6–8 inches apart in rows 12–18 inches apart. 

6. Planting Depth - Set bulbs with the tip just at or slightly above the soil surface (as seen in the image above). If you plant them too deep, the soil will compress around the bulb, and you will end up with smaller bulbs come harvest.

7. Watering - Water the bulbs after planting to help them settle in. Keep the soil evenly moist until the onions are established, but avoid soggy soil. 

How to Harvest Multiplier Onions

Potato onions will mature in 90–120 days from the start of their spring growth. Harvest your them in early to mid-summer when tops begin to yellow and fall over. 

For long-term storage, cure the bulbs in a warm, dry, well-ventilated area for 2–3 weeks before storing them in a cool, dry place. Keep in mind, potato onions can be grown as a perennial food crop by saving and replanting a portion of your harvested bulbs each year!