Introduction to Potato Onions

What are Potato Onions?

Potato Onions, (Allium cepa var. aggregatum) also called Hill Onion, Mother Onion, or Pregnant Onions, are a long-term storage multiplier onion that can be grown in the fall or spring (depending on where you live). Potato onions produce clusters of onions similar to shallots with some important differences. They are typically larger than shallots with a stronger flavor and store much longer, up to 12 months if conditions are right. Potato onions are long day, so not appropriate for southern Texas or Florida.

History and Origin of Potato Onions

Potato onions, also known as multiplier onions, have a rich history as a perennial variety of Allium cepa var. that has been commonly grown in home gardens for centuries. These onions are unique in that one bulb can produce several small bulbs, which can be planted in early spring or for fall planted potato onions to yield a new batch of onion bulbs.

Unlike regular onions, potato onions can be planted in raised beds, and they thrive when the soil is moist and fertile. With proper companion planting, they can produce true seed, although most gardeners prefer to grow potato onions using onion sets or medium-sized bulbs for a reliable harvest of larger onions.

Benefits of Growing Potato Onions

Growing potato onions offers numerous benefits for the home garden. As perennial onions, potato onions are low-maintenance and can be harvested over a year, with small bulbs growing into larger potato onions.

They are ideal for spring planting, and their ability to produce true seed and multiplier onions ensures a continuous supply of onion bulbs without needing to purchase new potato onion seeds each season.

Additionally, their adaptability to various soil types, including raised beds, and their suitability for companion planting with crops like carrots and garlic make growing potato onions a practical and rewarding choice for gardeners.

Understanding Potato Onion Varieties

Common Varieties of Potato Onions

Understanding potato onion varieties involves recognizing the unique characteristics and growing needs of each type. Commonly grown potato onions, such as yellow potato onions and multiplier onions, are prized for their ability to produce multiple bulbs from a single onion bulb.

To successfully grow potato onions, it's crucial to understand how to grow potato onions by planting the right types of seed onions in the fall for optimal results.

Whether you're using potato onion seeds or starting with small bulbs, ensuring the soil remains moist and well-drained will help you achieve larger potato onions and a bountiful harvest.

Differences Between Potato Onions and Regular Onions

Understanding potato onion varieties highlights their distinct differences from regular onions. Unlike regular onions, which are typically grown from onion sets or seeds and harvested as single, large bulbs, potato onions—such as yellow potato onions and multiplier onions—produce multiple bulbs from one planted onion bulb.

To successfully grow potato onions, you need to plant potato onion seeds or small bulbs in the fall, ensuring the soil remains moist to support the growth of larger potato onions.

Additionally, while regular onions are usually grown as annuals, potato onions are perennial onions that can continue to yield for several years, offering a unique advantage in home gardens.

Choosing the Right Variety for Your Garden

Choosing the right variety of potato onions for your garden involves considering several factors to ensure optimal growth and yield. For those interested in how to grow potato onions, using potato onion seed or selecting from types like yellow potato onions and multiplier onions can impact your success.

Potato onion seeds offer the advantage of growing new plants from the beginning, while fall planted potato onions or those started from small bulbs can provide a steady supply of onion bulbs throughout the season.

Assessing factors such as bulb size, soil moisture, and planting time—whether in early spring or fall—can help you achieve the best results for growing potato onions in your home garden.

Growing Basics

Soil: Potato Onions grow in a wide range of soils, but prefer mildly acidic to neutral soils that are well drained and rich in organic matter.

Spacing: Space rows 12–18” apart, sow every 4–6” for small bulbs and 8” apart for larger bulbs.

Companion Planting:


• Incompatibility — beans, peas
• Companions — cabbage, carrots, leeks, lettuce, marjoram, parsley, parsnip, roses, tomatoes

Water Requirements: Keep potato onions well watered, if soil dries out then growth will stop. It's best to use drip irrigation rather than overhead watering.

Fertilization: After planting, feed with a fertilizer that is higher in phosporus, a 5-10-5 mix is a good choice.

Weeding: Keep well weeded, does not compete well with weeds.

Plant in full sun.Very small bulbs may not multiply the first year, but will the second season.

Planting & Growing

Potato onions can be planted in the spring or fall depending on where you live and how harsh the winters are. Fall planting can give bigger yields but if the winter is very harsh, some bulbs may be lost.

Spring Planting: If your winters are very harsh, plant potato onions in spring when ground is workable. Plant bulbs deep enough so about ½–1” of soil covers the bulb. In colder winter areas, plant potato onions a little deeper, so about 2–5” of soil covers the bulb. Mulch heavily (4–8”) making sure to remove most of the mulch in the spring.

Fall Planting: If winters are mild to moderate you can plant potato onions in the fall from October to December. Plant bulbs deep enough so about ½–1” of soil covers the bulb.

Caring for Potato Onions

Watering Needs and Techniques

Caring for potato onions involves ensuring they receive the right amount of water to thrive. For effective watering, it's crucial to keep the soil moist, as this supports the growth of both potato onion seed and established onion bulbs.

When learning how to grow potato onions, remember that consistent moisture is especially important for fall planted potato onions and when starting new plants from small bulbs or potato onion seeds. Techniques such as using raised beds can help manage soil moisture levels, preventing overwatering and promoting healthier, larger potato onions.

Fertilization Strategies

Fertilization is crucial for the successful growth of potato onions, and timing plays a key role. When learning how to grow potato onions, it's important to apply fertilizer strategically to support healthy development.

For those using potato onion seeds or planting small bulbs in early spring, a balanced fertilizer should be applied at planting and again when the plants are establishing themselves.

For fall planted potato onions or perennial onions, a mid-season application can help boost bulb size and overall yield, ensuring that larger potato onions and a robust harvest are achieved.

Mulching for Weed Control and Moisture Retention

Mulching is an effective strategy for caring for potato onions, offering benefits such as weed control and moisture retention. When growing potato onions from seeds or small bulbs, applying mulch helps keep the soil moist and suppresses weeds that might compete for nutrients.

For fall planted potato onions and those established in raised beds, a layer of mulch can protect the soil and support the development of larger potato onions. Proper mulching also aids in maintaining consistent soil temperature, which is essential for successful germination and growth of both potato onion seeds and established plants.

Harvesting

As the potato onions are getting close to harvest the tops will fall over. When you see the tops start to fall over, cut off the water and make sure all of the mulch is removed (about 2 weeks before lifting). Once about half of the tops have fallen over, the potato onions are ready to lift. You can harvest the whole cluster or take only a few for immediate use. Make sure to harvest on a dry day.

To cure, bring the bulbs into a shaded, dry warm area with good air circulation. Spread them out in a single layer and let them cure for about 1–2 months. During the curing perion make sure to monitor for any spoiled bulbs and remove them. After curing, cut the tops off about 1” above the bulb and separate the onion clusters.

Storage

After curing store between 35–40°F or 50–70°F with about 60–70% humidity. Onions may sprout if stored between 40–50°F, so do not put them in the refrigerator. Best to store in a mesh bag or on a shelf (in a single layer) with good air circulation and placed in a root cellar, cool room, or garage. Potato onions will keep for up to 12 months if conditions are right.

Common Pests & Diseases

Flea Beetle: Chews leaves and head. Control with sticky traps, barriers such as floating rowcover, or organic insecticides labeled for flea beetles.

Onion Fly: Usually a problem during very wet growing seasons. 
Control with a product labeled for onion flies (or maggots).

Onion Thrips: Can control with insecticidal soap.

Slugs: Control by either hand picking them off or use a product labeled to 
control slugs.

Preventative Measures and Treatments

Effective pest and disease management for potato onions involves implementing preventative measures and treatments to protect your crop. When planting potato onion seeds, it's crucial to ensure the soil is well-drained and free from disease to prevent issues with pests and diseases.

Regularly inspecting for pests and diseases and applying treatments as needed can help maintain the health of yellow potato onions and other varieties.

Additionally, incorporating companion plants like garlic can naturally repel pests, while timely planting and harvesting—such as setting seeds in early November or before the last frost—can reduce the risk of disease and ensure a successful yield in your garden.

Pest Control – IPM

Integrated Pest Management (IPM) is an effective and environmentally sensitive approach to pest management that starts with the least invasive or impactful control methods and considers the use of chemical controls as the last step. For more information watch our Integrated Pest Management video.

Important to practice good cultural controls for pest management of potato onions. Cultural controls such as removing plants after harvest (to avoid leaving food for insects to continue to multiply on), use healthy bulbs to plant, practice crop rotation (e.g. do not plant onions in same area for 3–5 years).

Definitions

Heirloom: Heirloom seeds come from open-pollinated plants that pass on similar characteristics and traits from the parent plant to the next generation plant. Heirloom vegetables are old-time varieties generally which have been in production since before WWII, and have been saved and handed down through multiple generations.

Hybrid: a cross between two or more unrelated plant varieties. The two different varieties are cross bred, resulting in a seed that carries one or more favorable traits (increased yield, uniformity, color, disease resistance.) Hybrid seeds are not GMO, as they are manually cross-bred, not genetically modified in a lab. Hybrid seed is often sterile or does not reproduce true to the parent plant. Therefore, never save the seed from hybrids.

Open Pollinated: generally refers to seeds that will “breed true”. When the plants of an open-pollinated variety self-pollinate, or are pollinated by another representative of the same variety, the resulting seeds will produce plants roughly identical to their parents. Genetic traits may differ only slightly due to variations created by local conditions.

GMO: Genetically Modified Organisms were genetically modified in a laboratory where DNA genes are extracted and mixed with other unrelated plants to improve characteristics. Saved seed will not always be viable and may be trademarked to prevent unauthorized use.

Conclusion

Growing potato onions offers gardeners a rewarding experience with their unique benefits and versatility. By understanding the distinct characteristics of potato onions—such as their ability to produce multiple bulbs from a single planting and their suitability for various soil types and growing conditions—you can make the most of this perennial crop.

Proper care, including effective watering, strategic fertilization, and diligent pest management, ensures a bountiful harvest. Whether using potato onion seeds, fall planting, or companion planting, following these guidelines will help you achieve larger, flavorful onions and maintain a thriving garden.

With their rich history and reliable yields, potato onions are a valuable addition to any home garden.

FAQs About How to Grow Potato Onions: A Growing Guide

• Q1: When should I plant potato onion seeds?

  • A: Potato onion seeds, including Yellow Potato Onion varieties, are best planted in early November or in the spring after the last frost. For Green Mountain or Yellow Potato Onion types, early spring planting helps them develop before the summer solstice.

• Q2: How do I care for potato onions during their growing season?

  • A: Potato onions, like Yellow Potato Onion, thrive in well-drained soil and should be planted in the ground or raised beds. Keep the soil moist, especially as they start to develop a flower stalk. Look out for small onions and little bulbs that can be harvested early, or left to grow into larger bulbs.

• Q3: Can potato onions be grown in West Virginia?

  • A: Yes, potato onions, including the Yellow Potato Onion variety, grow well in West Virginia. They are well-suited for temperate climates, and Green Mountain varieties also thrive in this region.

• Q4: What is the best use for potato onions in cooking?

  • A: Potato onions have a sweet, mild flavor, making them ideal for cooking. They can be used like shallots or garlic in recipes, adding depth to soups, stews, and roasted dishes. You can also use the tops as green onions for fresh garnishes.

• Q5: Can potato onions set seed, and how can I use them for future planting?

  • A: Yes, Yellow Potato Onion plants can set seed through sexual reproduction, often when they produce a flower stalk. These seeds can be saved for future planting, allowing you to maintain a continuous supply of potato onions in your garden.