How to Plant An Onion Bulb or Several: Simple Steps for Beginners

Large Cured 1 pound Candy Onion
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Last Updated on 6 months by Michelle

Planting onions from bulbs is a straightforward and rewarding gardening task that can yield a plentiful harvest of flavorful bulbs for your kitchen.

The process begins with selecting the right type of onion bulb suited for your climate. Whether you opt for short day onions for warmer regions or long day onions if you reside in areas with longer sunlight hours, there’s an onion variety that fits your gardening zone.

Onions thrive in full sun and require well-drained soil rich in organic matter to facilitate their growth.

For a successful start, choose a spot in your garden that receives direct sun for the majority of the day and prepare the soil with aged compost to ensure good drainage and nutrient-rich conditions for your onion plants.

When planting onion bulbs, it’s important to give them enough space to grow.

Generally, planting the bulbs about four to six inches apart in rows facilitates good air circulation and minimizes the competition for nutrients.

If your garden space is limited or if you’re dealing with heavy soil, consider raising your growing area with raised beds to improve soil drainage and warm the soil in early spring. 

Onion sets, which are small, immature bulbs, are an excellent choice for beginners or gardeners looking for a quicker harvest, whereas starting onions from seed might be preferable for those seeking specific varieties or planting on a larger scale.

Caring for your onion crop involves keeping the soil moist but not waterlogged to avoid problems like onion maggots, which can damage the root growth.

Mulching can help retain moisture and keep the soil temperature regulated.

As the onion plants develop, green sprouts will emerge, indicating healthy growth.

Green onions can be harvested young for a mild flavor or you can wait until the bulb onions form full-sized bulbs.

As the onion tops begin to turn yellow and fall over, it’s a sign that your onions are ready for harvesting.

Remember, proper spacing, consistent watering, and patient cultivation are the keys to a bountiful onion harvest.

Getting Started with Onion Planting

Beginning your journey with planting onion bulbs is an exciting foray into gardening that promises a rewarding harvest. 

You will need to make key decisions about the onion varieties to plant, understand your soil’s properties, and select an ideal location to ensure a successful onion crop.


Choosing the Right Onion Varieties

When you start out with onion planting, it’s important to choose varieties that are suited to your climate.

Onion bulbs can vary significantly. Short day onions like the ‘Yellow Sweet Spanish’ are perfect for southern regions, while long day onions thrive in the northern areas.

If you’re looking for quicker harvests, planting onion sets or onion seeds can yield young onions or green onions in just a few weeks.

For those with less space, even growing onion plants in containers can produce green sprouts suitable for culinary use.


Understanding Soil Requirements

Soil is a fundamental factor in successfully growing onions.

Your soil should be rich in organic matter, implying you might want to add compost or aged compost to enrich it.

Onions prefer a pH level between 6.0 and 7.0. Ensure that you have well-drained soil; onion plants are sensitive to water-logging, which can hinder root growth and increase the risk of diseases like onion maggots.

Selecting the Perfect Planting Site

The site for planting onions should have good drainage and be able to receive direct sun. Onions require full sun, meaning at least six sunlight hours daily, to form bulbs effectively. 

Consider raised beds or mounded rows in areas with heavy clay soil to improve drainage. 

Additionally, crop rotation is key—onions should not be planted in the same location where you have grown related crops in the previous year to avoid pest buildup, such as the onion maggot.

Preparing for Planting

Before you start to plant onion bulbs, it’s crucial to ensure your soil is well-prepared and fertile to support robust growth. 

Proper soil preparation and fertilization are the bedrock for successful onion cultivation.

Soil Preparation Techniques

To begin, you’ll want to aim for soil that is well-drained with a pH of 6.0 to 7.0.

Use a tiller or garden fork to loosen the soil to a depth of about 8 to 12 inches and remove any weeds or debris.

This will provide your onion plants with loose soil that promotes good root growth.

If you’re dealing with heavy clay soil, consider using raised beds to improve drainage.

Adding organic matter is another vital step in the preparation process.

Mixing in plenty of well-aged compost will introduce beneficial nutrients and enhance the soil structure, making it easier for young onions to develop strong roots and grow.

If you are growing in pots, incorporate compost into the potting mix to ensure that onion seedlings have a nutrient-rich environment.

Fertilizing Your Soil

Once your soil is prepared, the next step is to fertilize.

Onions require a rich source of nitrogen to develop their leaves—after all, more leaves mean a larger onion bulb.

Achieve this by adding a balanced slow-release fertilizer to the soil prior to planting, or by enriching the soil with organic fertilizers like bone meal or blood meal, which release nutrients more slowly.

Remember, too much of a good thing can be detrimental. Excessive fertilizer can lead to lush foliage at the expense of the bulbs. Use fertilizers as directed and incorporate them into the soil evenly to encourage uniform growth among your plant onion bulbs.

Keep the soil moist but not waterlogged, as onions prefer a steady amount of moisture while eschewing overly wet conditions.

Planting Onion Bulbs

When you decide to plant onion bulbs, you’re setting the stage for a rewarding garden experience.

Onion plants are versatile and can be grown for their tender green shoots or allowed to mature into full-sized bulbs.

Below, you’ll find a step-by-step guide to doing it right, along with tips on spacing and depth to ensure your onions have the perfect environment to thrive.

Step-By-Step Planting Guide

1. Choose the Right Onion Bulbs: Select healthy onion sets or bulbs. For larger, sweeter onions, like the Yellow Sweet Spanish variety, look for firm, tiny onions free of any green sprouts.

2. Prepare the Soil: Ensure your garden has well-drained soil, ideally amended with aged compost or organic matter. Onions require loose soil that allows for unhindered root growth.

3. Time It Right: Plant onions as soon as the ground can be worked in early spring. In colder regions, you can start onion seeds indoors a few weeks before transplanting them.

4. Plant the Bulbs: Make a small hole and place one onion bulb with the pointy end up. Cover with soil and gently press down.

5. Watering: Keep the soil moist but not waterlogged to promote steady growth without risking onion rot.

6. Weed and Feed: Maintain a weed-free area around the onion plants and consider a balanced fertilizer to support their development.

7. Protection: In regions where onion maggots are a concern, using row covers can be beneficial.

Spacing and Depth Considerations

  • Spacing: Plant onion sets or bulbs about 4-6 inches apart in rows. This allows enough space for the onions to grow and for you to weed easily.

  • Depth: Plant each onion bulb about 2 inches deep into the soil. This is ideal for both onion sets and seeds, ensuring the onions are well anchored and can form bulbs effectively.

Keep an eye on your onions as they grow. Once green tops reach about 6 inches in height and start to turn yellow, you can begin harvesting young onions or leave them in the ground to form full-sized bulbs.

Remember, growing onions from bulbs is simple, but attention to detail with planting depth, sunlight hours (onions grow best in full sun), and soil quality can make all the difference in yielding a successful onion crop.

Onion Growth Management

Cultivating onions from bulbs effectively requires attentive care, specifically watering, mulching, and controlling weeds and pests. These factors are crucial for the health and yield of your onion crop.

Watering and Mulching

Proper watering is vital for onion plants as it promotes healthy root growth and bulb development.

Keep the soil moist, but make sure it is well-drained to avoid rot. In the early stages, it’s important to water your plant onions deeply once a week.

As the bulbs form, you may reduce the frequency but maintain even soil moisture.

Applying an aged compost layer or mulch can be beneficial for retaining moisture and keeping the soil temperature stable.

Dealing with Weeds and Pests

Weeds can severely hamper onion growth by competing for nutrients and water, so maintain a weed-free garden.

A mulched layer can suppress weed growth and also provide a barrier against pests. Be vigilant about onion maggots and thrips among the pests, which can damage the bulbs and leaves.

Use crop rotation and row covers as non-chemical approaches to manage these pests.

In severe cases, consult organic gardening guidelines for appropriate intervention.

Caring for Onion Plants

After planting onion bulbs, providing the right care is essential for your onion plants to thrive.

Consistency in care will help you achieve a bountiful crop of bulb onions.


Meeting Sunlight and Temperature Needs

Full Sun: Onion plants need an abundance of sunlight. Aim to provide your onion crop with full sun, which means at least 6-8 hours of direct sunlight per day. The more sunlight they receive, the better it is for bulb formation. If you’re growing onions indoors, choose a spot near a sunny window ensuring they still get the needed sunlight hours.

Temperature: Onions are cool-season crops but they can adapt to a range of temperatures. You should ideally plant onion sets in early spring, as soon as the soil is workable. Onion bulbs require consistent temperature and should not be subjected to extreme fluctuations as this can affect growth.


Nutrient Management and Crop Rotation

Nutrient-Rich Soil: For the best growth, onions require soil that’s rich in organic matter. A well-drained soil that’s been amended with aged compost will provide the necessary nutrients for your onions to form bulbs. Additionally, a consistent supply of nitrogen will promote healthy, vigorous green shoots.

Crop Rotation: Avoid planting onions in the same location every year. Practicing crop rotation can help prevent the accumulation of diseases and pests, including onion maggots. Moreover, rotating with plants that add different nutrients to the soil helps maintain its fertility, ensuring stronger onion plants and more onions at harvest time.

Remember to keep the soil moist but not waterlogged, as onions, like many other plants, do not tolerate ‘wet feet.’ Maintaining a weed-free environment is also crucial to prevent competition for nutrients and sunlight. With proper care and attentive gardening tips, you’ll be able to harvest young onions or let them grow into full-sized bulbs, ready to add flavor to your cooking.

Harvesting and Curing Onions

Cultivating onions from bulbs culminates in a rewarding harvest. Knowing when and how to properly harvest and cure your onions ensures they store well, maintaining their flavor and longevity.


Large Cured 1 pound Candy Onion

Recognizing Harvest Time

When it’s time to harvest, onion tops naturally fall over and begin to turn yellow.

This typically occurs in late summer or early fall, and is your cue that the onion bulbs have stopped growing.

For bulb onions such as Yellow Sweet Spanish, it takes approximately 100 to 125 days from seed or 60 to 80 days from sets to reach maturity.

If you’re growing green onions, they may be ready in as little as three weeks.

Proper Techniques for Harvesting and Curing

First, gently loosen the soil around the onions using a fork or hand trowel, being careful not to damage the onion bulbs.

Pull the bulbs out and shake off any excess soil. Allow them to dry in a warm, dry, well-ventilated area with direct sun for about a week to form a protective layer.

To cure onions, lay them out in a single layer, and if you have braided or hung them, ensure they have ample air circulation.

After the outer onion layers have dried, trim the roots and cut back the onion tops to about an inch.

For optimal storage life, keep your onions in a cool, dry place, such as in mesh bags or on mounded rows of shelves where they won’t touch each other.

Cured onions can last for several months when stored in good drainage conditions with adequate airflow.

Storing and Using Onions

After you’ve harvested your onion bulbs, proper storage is crucial to maximize their shelf life and flavor.

This section will provide practical tips for storing your onions effectively and suggest ways to enjoy the fruits of your gardening labor.

Tips for Long-Term Storage

Size and Diameter Matter: When storing onions, keep in mind that larger onions and those with a greater diameter might not store as well as smaller, more compact bulbs.

Carefully select dry and well-cured onions for storage, and use any bulbs that feel soft or show signs of damage first to avoid spoilage.

  • Ideal Conditions: Store your onion bulbs in a cool, dry place with lots of air circulation. Effective storage methods include hanging them in a mesh bag or placing them on a mounded row to ensure good drainage and prevent rot.

  • Temperature: Aim to keep your stored onions at temperatures between 35-40°F (2-4°C).

  • Avoid Moisture: Keep onions in an area with low humidity. Basements are often too damp for onion storage.

  • Ventilation: Make sure the storage area is well-ventilated to prevent any build-up of ethylene gas, which can accelerate decay.

Enjoying Your Home-Grown Onions

From Bulb to Plate: Once your onions are stored properly, you can enjoy them in a multitude of dishes. 

Sweet onions, for example, add a delightful flavor when caramelized, or can be chopped raw into salads for a crisp, pungent kick.

  • Green Onions and Scallions: Young onions or scallions can be harvested early and used for their mild yet distinct flavor. They’re perfect for garnishing and adding a fresh zing to your meals.

  • Cooking with Onions: Onions from bulbs form the backbone of many savory dishes. Whether you’re sautéing, roasting, or grilling, onions offer a depth of flavor that is essential in the kitchen.

  • Flavor Profiles: Different onion varieties bring unique taste profiles. Yellow sweet spanish onions, for instance, are known for their robust flavor, ideal for soups and stews, while short day onions might be milder and better suited for raw culinary uses.

By following these tips, you can store your onion crop effectively and incorporate these flavorful bulbs into your cooking repertoire, ensuring not a single onion goes to waste.


Troubleshooting Common Issues

Frost Damage: If you’ve planted your onion bulbs early in the year, frost can be a major concern. Protect your young onions by using row covers or temporarily cover them with a frost cloth to shield them from sudden temperature drops.

Stunted Growth: Are your onion plants not growing as expected? Ensure they’re in a location that gets full sun. Onions thrive with plenty of sunlight hours. If necessary, consider transplanting them to a better spot with more direct sun exposure.

Weak Bulb Development: Maintaining well-drained soil is key for full-sized, robust bulb onions. Heavy clay or waterlogged conditions can hamper bulb development. To fix this, add compost or plant in raised beds for good drainage.

Soil Moisture: Ensure soil is moist but not soggy. Use mulch to retain moisture between waterings. Onion Bolts Avoid planting too early to prevent bolting, which happens when the plant shifts from leaf growth to flower and seed. Choose the right type of onion seed or sets for your climate. Pests Onion maggots can be a nuisance. Use crop rotation and keep the area weed free to minimize infestation. Be diligent with cleaning up plant debris to prevent pests.

Root Issues: Poor root growth can be a result of very compacted soil. Ensure your soil is loose and enriched with organic matter to promote healthy onion roots.

Overcrowding: If onion sets are planted too closely—less than inches apart—they might not have enough space to develop into full-sized bulbs. Thin out the plants if needed.

Watering: Onions require consistent moisture. Keep the soil moist, but be careful not to overwater, as onion bulbs are prone to rot in wet conditions. During particularly dry weather, increase watering frequency.

Remember, regular observation and a gentle hand with watering and care can lead to bountiful harvests of onions come late summer!



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