How to Grow Onions in Australia

• Types of Onions
• Preparing Your Garden
• Planting Onions
• Caring for Your Onion Plants
• Harvesting and Storing Onions
• Companion Plants For Onions
• Common Onion Growing Problems and Solutions

Whether you're a seasoned gardener or just starting out, this comprehensive guide will provide you with all the information you need to successfully grow onions in your own backyard. From understanding different onion varieties to planting techniques, caring for your onion plants, and harvesting and storing the bulbs, we'll cover every step of the process. By following these expert tips and techniques, you'll soon be enjoying a bountiful harvest of homegrown onions that will enhance your culinary creations and leave you with a sense of accomplishment. 

When to Plant Onions in Australia

Tropical

Best planting months for Onions in the Tropical regions are April, June, and July. This includes areas like Cairns, Darwin, and Broome.

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Subtropical

For the Subtropical region, onions can be planted all year round. Cities in the Subtropical region include Brisbane, Central Coast, and Sydney.

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Temperate

Onions can be planted year round in the Temperate regions of Australia. Cities in the Temperate region include Melbourne, Adelaide, Geelong, and Perth.

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Cool

For the Cool region, onions can be planted from August to September and from April to December. Cities in the Cool region include alpine regions of Victoria and Tasmania.

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Arid

Best planting months for onions in the Arid region are February to August. This includes areas like Alice Springs, Kalgoorlie, and Broken Hill.

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Types of Onions

Onions come in a range of types, each with its own unique flavour and culinary uses. Here are some of the most common types you might encounter:

1. Yellow Onions: These are the most widely used and versatile onions. They have a strong, pungent flavour that mellows when cooked, making them perfect for sautéing, caramelising, and adding depth to soups and stews.
2. White Onions: With a milder and sweeter flavour than yellow onions, white onions are often used in Mexican and Southwestern cuisine. They are great for fresh salsa, guacamole, and ceviche.
3. Red Onions: Known for their vibrant colour and mild flavour, red onions are a popular choice for salads and sandwiches. They add a crisp, tangy bite and a splash of colour to any dish.
4. Sweet Onions: As the name suggests, sweet onions have a mild, sweet flavour with less of the pungency found in other types. They are delicious when eaten raw in salads or used in recipes that call for a subtle onion flavour.
5. Shallots: Shallots are small, elongated onions with a delicate, sweet flavour. They are often used in gourmet cooking, adding a subtle onion flavour to sauces, dressings, and vinaigrettes.

Each type of onion has its own unique characteristics, so don't be afraid to experiment and find the ones that suit your taste buds and culinary preferences.

Preparing Your Garden

Before embarking on the journey of growing onions in your home garden, it is crucial to adequately prepare your garden. Proper soil preparation and selecting the right planting location and spacing are essential steps that will set the foundation for successful onion cultivation.

Soil Preparation

Soil preparation is a vital aspect of growing onions. Onions thrive in well-draining soil that is rich in organic matter. Start by clearing the designated area of any weeds or debris. This will ensure that the onions have ample space to grow and develop without competition from other plants.

Once the area is cleared, it's time to focus on improving the soil quality. Onions prefer soil with a pH level between 6.0 and 7.0, which is slightly acidic to neutral. Before planting, conduct a soil test to determine the pH level of your garden soil. If the pH is outside the desired range, you can adjust it by adding amendments such as lime to raise the pH or sulphur to lower it.

In addition to pH adjustment, enrich the soil with organic matter such as well-rotted compost or aged manure. These organic materials enhance the soil structure, promote water retention, and provide essential nutrients for healthy onion growth. Spread a layer of compost or manure over the garden bed and work it into the soil using a garden fork or tiller. This will ensure that the organic matter is evenly distributed and incorporated into the soil.

Planting Location and Spacing

Choosing the right planting location and spacing for your onions is crucial for their overall development and productivity. Onions require at least six hours of direct sunlight each day to thrive. Therefore, select a location in your garden that receives ample sunlight.

When it comes to spacing, onions need enough room to grow and develop their bulbs. The recommended spacing between onion plants is approximately 4 to 6 inches (10 to 15 centimetres) apart. This spacing allows the plants to have enough air circulation and reduces the risk of diseases. It also provides ample space for each plant to develop a sizable bulb.

To ensure uniform spacing, you can use a garden tool like a dibber or your fingers to create small holes in the prepared soil. Place each onion plant into a hole, gently firm the soil around it, and ensure that the bulb is positioned just below the soil surface.

By giving your onions the proper care and attention during the preparation stage, you are setting them up for success. Healthy, well-prepared soil and strategic planting will provide the foundation for robust onion growth and bountiful harvests.

Planting Onions

When it comes to planting onions, there are a few different methods you can choose from: starting from seeds, transplanting seedlings, or planting onion sets. Each method has its own advantages and considerations, so let's explore them further.

Starting from Seeds

Starting onions from seeds is a great option if you want a wide variety of onion choices. It gives you the opportunity to grow unique and specialty onion varieties that may not be available as seedlings or sets. To start onions from seeds, begin by sowing the seeds indoors in trays or pots about 8 to 10 weeks before the last frost date in your area. If you're unsure about the last frost date, you can find this information from your local agricultural extension office.

Ensure that the seeds are covered with a thin layer of soil and keep them moist but not waterlogged. As the seedlings grow, make sure they receive adequate light. If you don't have access to natural light, you can use fluorescent lights or grow lights to provide the necessary light spectrum for healthy growth. Once the seedlings have grown to a sufficient size and the risk of frost has passed, they can be transplanted into your garden.

Transplanting Seedlings

Transplanting onion seedlings is a convenient and time-saving method. You can purchase seedlings from a local nursery or start your own from seeds and then transplant them into your garden. This method allows you to get a head start on the growing season, as the seedlings have already begun to establish their root systems.

Before transplanting the seedlings, make sure to prepare your garden beds by loosening the soil and removing any weeds or debris. Dig small holes or furrows in the soil according to the spacing recommendations for the specific onion variety. Gently remove the seedlings from their containers, taking care not to damage the delicate roots, and place them into the prepared holes. Cover the roots with soil and press lightly to ensure good soil-to-root contact.

Planting Onion Sets

Onion sets are small onion bulbs that have been grown from seeds and then harvested before they reach full maturity. They are essentially baby onions, and planting them is a quick and easy way to get your onion garden started. You can find onion sets at your local garden centre or order them online.

To plant onion sets, first prepare your garden beds by removing any weeds and loosening the soil. Place the sets in the soil, pointy side up, and make sure they are spaced according to the recommendations for the specific variety. Cover the sets with soil, leaving the tip of the bulb exposed.

It's important to note that onion sets are more prone to bolting, or premature flowering, than onions started from seeds or seedlings. If you experience bolting, it may be helpful to provide some shade or cover the plants during hot weather to prevent stress. Additionally, choosing bolt-resistant onion varieties can help minimise this issue.

No matter which method you choose, planting onions is a rewarding experience that allows you to enjoy the flavours and versatility of homegrown onions. Now that you have a good understanding of the various planting methods, you can decide which one suits your gardening style and preferences. Happy planting!

Caring for Your Onion Plants

Once you've successfully planted your onion seeds or sets, it's important to provide proper care to ensure healthy growth and a bountiful harvest. Caring for your onion plants involves three key aspects: watering and irrigation, fertilising, and weed control.

Watering and Irrigation

Onions require consistent moisture to thrive, so it's important to establish a regular watering routine. Water deeply to ensure that the moisture reaches the onion's root system. This encourages the development of strong, healthy roots and prevents shallow root growth. However, be mindful not to overwater, as this can lead to rot and other fungal diseases.

To determine when to water, check the moisture level of the soil. Stick your finger about an inch into the soil near the onion plants. If it feels dry, it's time to water. Watering in the morning is generally recommended, as it allows the foliage to dry during the day, reducing the risk of disease.

If you're looking for efficient ways to conserve water while still providing adequate moisture to your onion plants, consider using drip irrigation or soaker hoses. These methods deliver water directly to the root zone, minimising water loss through evaporation and ensuring that the plants receive the moisture they need.

Fertilising

To promote healthy growth and maximise onion bulb development, it's crucial to provide your plants with the nutrients they need. Fertilising is an essential part of onion care.

Before planting, incorporate organic matter such as compost or well-rotted manure into the soil. This enriches the soil with nutrients and improves its overall fertility. Additionally, consider performing a soil test to determine any specific nutrient deficiencies that need to be addressed.

During the growing season, you can supplement the soil with a balanced fertiliser. Look for a fertiliser with a nitrogen-phosphorus-potassium (N-P-K) ratio of around 10-10-10 or 12-12-12. Apply the fertiliser according to the package instructions, being careful not to over-fertilize, as this can lead to excessive foliage growth at the expense of bulb development.

Weed Control

Weeds can compete with your onion plants for nutrients, water, and sunlight, so it's important to keep them in check. Weed control is an ongoing task throughout the growing season.

Start by clearing the area of any existing weeds before planting your onions. This reduces competition and gives your plants a better chance to establish themselves. Once the onions are planted, it's important to keep the area around the plants weed-free.

Regular hand weeding is one effective method for controlling weeds in your onion garden. Take care to remove weeds while they are still small to prevent them from becoming established and competing with your onions. You can also use mulch to suppress weed growth. Apply a layer of organic mulch, such as straw or wood chips, around the onion plants, taking care not to cover the bulbs.

By implementing proper watering and irrigation techniques, providing adequate fertilisation, and practising effective weed control, you'll be well on your way to growing healthy, robust onions in your garden.

Harvesting and Storing Onions

Once you've successfully nurtured your onion plants and watched them grow, it's time to reap the rewards of your hard work. Harvesting and storing onions is a crucial step in the gardening process, ensuring that you have a bountiful supply of these versatile vegetables for your culinary endeavours. In this section, we will explore the key aspects of harvesting and storing onions, including knowing when to harvest, proper harvesting techniques, and the process of curing and storing onions.

Knowing When to Harvest

Determining the perfect time to harvest your onions is essential to ensure optimal flavour, texture, and storage potential. The timing may vary depending on the onion variety, as well as your personal preference for taste. Onions are typically ready for harvesting when the foliage begins to turn yellow and topple over. This signifies that the plants have completed their growth and are ready to be harvested.

To further confirm that your onions are ready for harvest, gently press the soil around the bulb to feel its firmness. If the bulbs are plump and the outer skin is papery and dry, it's a good indication that they are mature and ready to be harvested. On the other hand, if the bulbs still feel soft or the foliage is still green and upright, it's best to wait a little longer before harvesting.

Proper Harvesting Techniques

To ensure that your onions remain in optimal condition, it's important to employ proper harvesting techniques. Start by gently loosening the soil around the bulbs using a garden fork or trowel. Be careful not to damage the bulbs while doing so. Once the soil is loosened, carefully lift the bulbs from the ground, taking care to avoid bruising or cutting them.

After harvesting, it's crucial to handle the onions with care. Avoid dropping or roughly handling the bulbs, as this can lead to bruising and spoilage. Additionally, it's important to remove any excess soil clinging to the bulbs, as this can provide a breeding ground for bacteria and fungi. You can gently brush off the excess soil or rinse the bulbs with water, ensuring that they are completely dry before proceeding to the next step.

Curing and Storing Onions

Curing is a vital step in the onion harvesting process, as it allows the bulbs to dry and develop a protective layer that extends their shelf life. To cure your onions, you will need to lay them out in a well-ventilated area with low humidity. This could be a sunny spot in your garden or a well-ventilated shed or garage.

Spread the harvested onions in a single layer, ensuring that they do not touch each other. This allows air to circulate around the bulbs, facilitating the drying process. Ideally, the curing process should take around two to three weeks. During this time, the outer layers of the bulbs will become dry and papery, while the inner layers will retain their moisture.

Once the onions are fully cured, it's time to store them for future use. You can store your onions in a cool, dry, and well-ventilated area, such as a pantry, cellar, or garage. Avoid storing onions in the refrigerator, as the cold temperature and high humidity can cause them to become soft and spoil quickly.

For long-term storage, you can also consider braiding your onions or placing them in mesh bags. This allows for better air circulation and helps prevent mould or rot. Remember to regularly inspect your stored onions and remove any that show signs of spoilage to prevent it from spreading to the rest of your harvest.

With these essential tips on harvesting and storing onions, you can now confidently enjoy the fruits of your labour throughout the year. Whether you plan to use them in savoury dishes, salads, or soups, your homegrown onions will undoubtedly add a burst of flavour and freshness to your culinary creations.

Stay tuned for the final section of our comprehensive guide, where we will address common onion growing problems and provide practical solutions to help you overcome them.

Companion Plants For Onions

Here are some excellent companion plants for onions:

• Carrots: Carrots and onions make a great team. They help each other by repelling pests that target one another, such as onion flies and carrot flies.
• Lettuce: Planting lettuce near onions provides shade to the onion bulbs and helps maximise garden space.
• Chives: Chives are part of the onion family and can enhance the flavour of both onions and nearby vegetables. They also help deter pests.
• Cabbage Family (Broccoli, Cauliflower, Cabbage): Onions can help repel pests that are common to the cabbage family, and vice versa.
• Tomatoes: Tomatoes and onions complement each other well when grown together, and planting them close can help deter certain pests.
• Beets: Onions and beets are mutually beneficial, as they don't compete for space or nutrients, making them good companions.
• Strawberries: Onions can help protect strawberries from pests and diseases, while strawberries act as a living mulch, benefiting the onions.
• Lettuce: Lettuce can be a helpful neighbour to onions by providing shade and keeping the soil moist.

Be sure to check out our grow guides for a full list of fruits, vegetables and herbs for your garden.  

Common Onion Growing Problems and Solutions

Growing onions can be a rewarding experience for home gardeners, but like any crop, onions are susceptible to certain problems. In this section, we will discuss some common issues that you may encounter while growing onions and provide effective solutions to overcome them.

Pest and Disease Control

Pests and diseases can wreak havoc on your onion plants, causing damage and reducing the overall yield. It's important to identify and address these issues early on to prevent them from spreading. Here are some common pests and diseases that affect onions and ways to control them:

1. Onion Thrips: These tiny insects feed on the leaves and bulbs of onion plants, causing stunted growth and discoloration. To control thrips, you can use insecticidal soap or neem oil. Additionally, regularly removing weeds and keeping the garden clean can help reduce thrip populations.
2. Onion Maggots: The larvae of onion maggots feed on the roots and bulbs of onion plants, leading to wilting and rotting. To prevent infestations, you can use floating row covers to physically block the adult flies from laying eggs near your plants. Crop rotation and proper sanitation practices are also important in minimising the risk of maggot infestations.
3. Fungal Diseases: Common fungal diseases that affect onions include downy mildew and white rot. These diseases can cause yellowing of leaves, wilting, and bulb rot. To control fungal diseases, it is crucial to practise good sanitation, such as removing and disposing of infected plant debris. Fungicides labelled for onion use can also be applied as a preventive measure.
4. Damping Off: Damping off is a fungal disease that affects onion seedlings, causing them to rot at the base and ultimately die. To prevent damping off, it's important to start with clean, disease-free soil and use sterile containers for seed starting. Proper watering practices, such as avoiding overwatering and allowing the soil to dry out between waterings, can also help prevent this disease.

Onion Bolting and Premature Flowering

Onion bolting refers to the premature flowering of onion plants, which can negatively impact bulb development. When onions bolt, the energy that should be directed towards bulb growth is diverted towards producing flowers and seeds. Here are some factors that can contribute to onion bolting and ways to prevent it:

1. Temperature Fluctuations: Onions are sensitive to temperature changes, especially when exposed to prolonged periods of cold or heat. To prevent bolting, it's important to choose onion varieties that are suitable for your climate. Onions are classified as either long-day or short-day varieties, depending on their sensitivity to day length. Selecting the appropriate variety for your region can help reduce the risk of bolting.
2. Day Length: Onions require a specific number of daylight hours to trigger bulb formation. If your onions are receiving too much or too little light, they may bolt. To prevent this, you can cover your onion plants with shade cloth to reduce the amount of light they receive. Alternatively, if you are growing onions in a greenhouse or indoors, you can control the day length using artificial lighting.
3. Nutrient Imbalance: Imbalances in soil nutrients, particularly excessive nitrogen, can contribute to onion bolting. It's important to provide your onion plants with a balanced fertiliser that is low in nitrogen and high in phosphorus and potassium. This will promote healthy bulb development and reduce the risk of bolting.

By being proactive and implementing the appropriate pest and disease control measures, as well as understanding the factors that contribute to onion bolting, you can increase your chances of a successful onion harvest. Remember, a healthy and thriving onion crop starts with proper care and attention to detail.