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When to Plant Onions in Missouri – Expert Tips

Did you know that onions, tomatoes, and radishes are more than just flavorful additions to your favorite dishes? They have been staple crops in Missouri for centuries, providing both culinary delight and economic value. Growing these vegetables in Missouri comes with a plethora of benefits, making them ideal choices for gardeners and farmers alike.

Missouri’s rich soil and moderate climate create the perfect conditions for growing both green onions and bulb onions in vegetable gardens. The state has a long history of cultivating these season crops, dating back to early settlers who recognized the potential of these versatile vegetables. Today, various onion varieties thrive in Missouri’s diverse landscape, offering options suitable for different tastes and preferences.

Whether you’re a seasoned gardener or just starting out, understanding the vegetable planting calendar for Missouri is crucial for successful gardening. By considering factors like temperature, daylight hours, and frost dates, you can maximize your yield and enjoy homegrown tomatoes, radishes, and onions throughout the year.

So let’s dive into the world of vegetable gardening in Missouri and explore the best practices that will help you cultivate radishes and other vegetables right in your own backyard.

when to plant onions in missouri

When to Plant Onions in Missouri? The Right Time to Plant Onions in Missouri:

Optimal Planting Time for Onions in Missouri

Planting onions in a vegetable garden at the right time is crucial for a successful harvest of crops, including tomatoes and radishes, in Missouri. The optimal planting time for onions depends on factors such as temperature, daylight hours, and local weather patterns. By understanding these influences, you can ensure your onions thrive and yield a bountiful crop.

Factors Influencing Timing

Temperature and daylight hours are important factors in determining the best time to plant onions in Missouri. Onions, a cool-season crop, thrive in moderate temperatures and need 13-16 hours of daylight for proper development. This information is useful when planning your vegetable planting calendar for your vegetable garden, especially if you want to grow tomatoes alongside your onions.

Avoid Early or Late Planting

To achieve the best results with winter crops like radishes and other vegetables, it’s important to avoid both early and late planting of onions. If planted too early, radishes and other crops may be exposed to frost damage or stunted growth due to cold temperatures. On the other hand, if planted too late, they might not have sufficient time to mature before the first frost arrives.

Determining the Right Time

To determine the ideal planting time for onions in Missouri, consider your region’s last frost date and soil temperature. This date signifies when it is generally safe from frost until the next growing season for radishes and other crops. For most parts of Missouri, the average last frost occurs between mid-April and early May, making it suitable for winter planting.

By waiting until after the last expected frost date has passed, you can minimize the risk of frost damage to your onion crops. Planting radishes shortly after this date allows ample time for your vegetables to grow before hot summer temperatures arrive.

Local Weather Patterns

While relying on general guidelines like last frost dates and the planting calendar is helpful, it’s also essential to consider local weather patterns specific to your area within Missouri. Microclimates can exist within different regions of the state due to varying terrain and proximity to bodies of water. It’s important to be mindful of soil temperature during the winter month.

Observing local weather conditions will give you a better idea of when it’s safe to plant onions outdoors in the winter. Keep an eye on the planting calendar and consider factors like soil temperature, which should ideally be around 50°F (10°C) for optimal onion growth.

when to plant onions in missouri

Planting Calendar for Onions in Missouri:

Month-by-Month Guide to Growing Onions

If you’re eager to grow your own onions in Missouri, it’s essential to know when to plant them. With the right planting calendar, you’ll be able to enjoy a bountiful harvest of delicious onions. Here’s a month-by-month breakdown of when to plant onions throughout the year, specifically in June, to maximize your yield of fresh vegetables.

Spring Planting Options


  • As soon as the soil can be worked, around mid-March, you can start planting green onions, also known as day onions. These vegetables are perfect for planting in June.
  • Onion sets, also known as green onions or day onions, are small bulbs that have already begun growing and will give you a head start on your vegetable crop. This guide will help you with your onion sets.


  • In the mid-month of April, direct sow vegetables like onions into well-prepared garden beds. Use this guide to know when and how to plant different vegetables throughout the month.
  • Make sure the soil temperature is above 40°F (4°C) before sowing onion seedlings. Plant onion sets in the soil and wait for them to grow into raw onions. This process usually takes about a month.
  • Plant the onion seedlings about half an inch deep and one inch apart.


  • By mid-May, continue sowing onion seeds if you missed the earlier window. This month, follow our guide to ensure successful onion planting.
  • Remember to water your onion seedlings regularly but avoid overwatering as it may lead to rotting. This guide applies to both onion sets and mid-season onion varieties.

Fall Planting Options


  • In the mid-month of August or early September, begin preparing your garden beds for fall planting with onion sets. Use this guide to ensure successful planting.
  • Choose short-day onion varieties suitable for Missouri’s climate.


  • Around mid-September is the perfect time to start transplanting onion seedlings or sets into your prepared beds. This month-by-month guide will help you with the process.
  • Ensure the onion sets are spaced about four inches apart and planted two inches deep. This guide is useful for planting onion sets in the mid-month.


  • If you missed the September window, don’t worry! You still have time in mid-October to plant onions for a fall harvest. This month-by-month guide will help you get started.
  • Follow the same guidelines mentioned above for spacing and depth, especially when it comes to mid-month.

Choosing Onion Varieties Based on Planting Season

When selecting which onion varieties to grow in Missouri, it’s crucial to consider the planting season. Different varieties have varying requirements and perform better in specific conditions. This month, use our guide to choose the best onion varieties for your mid-Missouri garden.

Spring Varieties:

  • Candy Onion
  • Walla Walla Onion
  • Texas Early Grano

Fall Varieties:

  • Red Creole Onion
  • Yellow Granex Hybrid
  • Texas Legend Onion

By following our guide and choosing appropriate onion varieties for each planting season, you’ll increase your chances of a successful harvest every month, from early to mid-season.

Frost Date Considerations

To ensure your onions thrive in Missouri, it’s important to be aware of the average frost dates in the mid-month. Onions are generally tolerant of light frosts, but a hard freeze can damage or kill them.

Last Spring Frost Date:

  • Southern Missouri: Mid-April to early May
  • Central Missouri: Late April to early May
  • Northern Missouri: Early to mid-May

First Fall Frost Date:

  • Southern Missouri: Mid-to-late October
  • Central Missouri: Late October to early November
  • Northern Missouri: Early to mid-November

Keep this guide to frost dates in mind when planning your planting schedule for the month. If you’re uncertain about the exact mid-month dates for your location, consult with local gardening resources or experienced gardeners in your area.

when to plant onions in missouri

Tips and Techniques for Growing Onions in Missouri:

Soil Preparation Tips

To ensure your onions thrive in Missouri’s unique soil conditions, proper soil preparation is key. Start by testing the pH levels of your soil mid-month using a kit available at your local garden center. Aim for a slightly acidic to neutral pH range of 6.0 to 7.0, as this promotes optimal nutrient availability for onion growth.

In addition to pH levels, organic matter content is crucial for healthy onion development. Incorporate well-rotted compost or aged manure into the soil before planting in mid-month to improve its structure and provide essential nutrients. This will help retain moisture while allowing for proper drainage.

Proper Spacing and Depth Requirements

Spacing and depth are crucial for the successful growth of onion plants. Make sure to leave about 4-6 inches between each plant to provide enough space for bulb expansion without crowding. This is important, especially during the growing month.

Planting depth is equally important when planting onions. Gently press each onion set or seedling into the prepared soil until just the top is visible above ground level. Avoid burying them too deep, as this can hinder their growth and result in smaller bulbs. It’s best to plant onions during the appropriate month for optimal growth.

Watering Techniques

Proper watering techniques are essential for promoting healthy root development in your onions. Keep the soil consistently moist but not waterlogged throughout the growing season, especially during dry spells. This is crucial to ensure that your onions thrive month after month.

Aim to provide approximately 1 inch of water per week throughout the month through rainfall or irrigation methods such as drip irrigation or soaker hoses. Water deeply to encourage roots to grow deeper into the soil, helping plants withstand drought conditions.

Fertilization Recommendations

To ensure your onions receive adequate nutrition in Missouri’s specific soil conditions, fertilization is necessary. Before planting, incorporate a balanced fertilizer with equal parts nitrogen (N), phosphorus (P), and potassium (K) into the soil according to package instructions. This should be done every month.

Once your onions have sprouted, side-dress them with a nitrogen-rich fertilizer every month. This will support leafy growth and bulb development. Avoid over-fertilizing, as it can lead to excessive foliage growth at the expense of bulb formation.

By following these tips and techniques tailored for Missouri’s climate and soil conditions, you’ll be well on your way to growing robust and flavorful onions in your garden within a month. Happy planting!

Harvesting and Curing Onions: Best Practices

Signs indicating when onions are ready for harvest

Knowing when to harvest your onion crop is crucial for achieving the best flavor and storage potential. Keep an eye out for these signs that indicate your onions are ready to be harvested in about a month.

  • Bulb size: Mature onion bulbs should have reached their full size, which varies depending on the variety. Check the seed packet or catalog description for specific information.
  • Leaf color: As onions mature, their foliage will start to turn yellow and flop over. This is a clear indication that they are nearing harvest time.
  • Soft neck vs. hard neck varieties: Soft neck varieties tend to be ready for harvest earlier than hard neck varieties. You can gently squeeze the bulb to determine its readiness – if it feels firm, it might need more time.

Step-by-step guide on how to properly harvest onions

To ensure you’re harvesting your onions correctly, follow these simple steps:

  1. Loosen the soil: Use a garden fork or shovel to carefully loosen the soil around each onion bulb without damaging them.
  2. Lift and separate: Gently lift each onion plant from the ground, being careful not to break off any leaves or damage the bulbs.
  3. Dry out excess soil: Shake off any loose soil clinging to the roots of the plants.
  4. Leave in place: Allow your freshly harvested onions to sit in place for a day or two before moving them indoors.

Importance of curing onions before storage

Curing is an essential step in preparing your onions for long-term storage. It helps remove excess moisture from the bulbs and promotes better storage conditions by toughening up their outer layers.

Here’s why you should never skip this crucial step:

  • Prevents rotting: Curing reduces moisture content, making it less likely for your stored onions to rot or develop diseases like white rot.
  • Enhances flavor development: The curing process allows the onion bulbs to develop their full flavor potential, resulting in a more satisfying culinary experience.
  • Extends shelf life: Cured onions have a longer shelf life compared to uncured ones. Properly cured onions can last for several months when stored correctly.

Tips for drying and storing harvested onions

Once your onions have been properly cured, it’s time to dry and store them for future use. Follow these tips to ensure their longevity:

  • Dry thoroughly: Spread out your cured onions in a single layer in a well-ventilated area with good air circulation. Avoid direct sunlight as it can cause sunburn on the bulbs.
  • Monitor humidity levels: Make sure the drying area has low humidity to prevent mold growth. Aim for a relative humidity of around 60% or lower.
  • Store in a cool, dry place: Once fully dried, trim off any remaining foliage and store your onions in a cool, dry location away from direct light. A basement or pantry works well.
  • Avoid storing with certain produce: Keep your harvested onions away from potatoes and other vegetables that release moisture or ethylene gas, which can accelerate spoilage.

Starting Onion Seeds Indoors: Timing and Methods

Growing onions in Missouri can be a rewarding experience, but it’s crucial to start them off on the right foot. One way to ensure success is by starting onion seeds indoors.

Advantages of starting onion seeds indoors

Starting onion seeds indoors offers several advantages that can contribute to a successful harvest. Here are some benefits to consider:

  • Extended growing season: By starting seeds indoors, you can get a head start on the growing season. This is particularly important for onions as they have a long maturation period.
  • Greater control over conditions: Indoor seed starting allows you to create optimal conditions for your onion seedlings. You can regulate temperature, lighting, and watering more precisely than if you were relying solely on outdoor conditions.
  • Healthier plants: Starting seeds indoors gives you the opportunity to provide individual attention to each seedling. This helps promote stronger root development and overall healthier plants.

To determine when to start your onion seeds indoors in Missouri, it’s essential to consider both the desired transplant date and the recommended timeframe for indoor germination. Generally, onions should be transplanted outdoors 4-6 weeks before the last expected frost date in your area.

Here’s a suggested timeline for starting onion seeds indoors:

  1. 8-10 weeks before last expected frost date: Begin sowing onion seeds indoors in seed trays or individual pots filled with a well-draining potting mix.
  2. 6-8 weeks before last expected frost date: Ensure proper lighting by placing grow lights or fluorescent tubes above the seedlings. Maintain a temperature between 65°F and 75°F (18°C – 24°C).
  3. 4-6 weeks before last expected frost date: Gradually harden off the onion seedlings by exposing them to outdoor conditions for a few hours each day. This helps acclimate them to the fluctuating temperatures and prepares them for transplanting.

Different methods available, such as using seed trays or individual pots

You have various methods to choose from. Here are two popular options:

  1. Seed trays: Seed trays provide a convenient way to start multiple onion seeds in one container. Fill the tray with a well-draining potting mix and sow the seeds according to the packet instructions. Once germinated, thin out the seedlings so they have enough space to grow.
  2. Individual pots: If you prefer more control over each seedling’s growth, using individual pots is an excellent choice. Fill small pots with potting mix, sow one seed per pot, and ensure proper spacing between pots. This method allows you to monitor and care for each plant individually.

Special Considerations for Planting Onions in Missouri:

Addressing common challenges specific to growing onions in Missouri

Planting onions in Missouri comes with its own set of challenges. The state’s climate and soil conditions can impact the success of your onion plants. Here are some key considerations to keep in mind:

  1. Soil Preparation: Before planting onions, it is crucial to prepare the soil properly. Missouri soils vary across the state, but most areas have clay or loamy soil. Ensure good drainage by adding organic matter like compost or well-rotted manure.
  2. Timing: Timing is essential. Aim to plant them early in the spring, as soon as the ground can be worked, typically around mid-March to early April. This allows onions enough time to establish before hot summer temperatures arrive.
  3. Spacing: Onions require adequate spacing for proper growth and bulb development. Leave about 4-6 inches between each onion plant, allowing room for bulbs to expand without overcrowding.

Dealing with potential pests and diseases prevalent in the region

Missouri’s climate creates favorable conditions for certain pests and diseases that can affect onion plants. Here’s how you can tackle them:

  1. Onion Maggots: These small white larvae can damage onion plants by tunneling into bulbs and causing rot. To prevent infestation, cover young plants with row covers until they are established or consider using floating row covers throughout the growing season.
  2. Thrips: Thrips are tiny insects that feed on onion leaves, causing silver streaks or browning on foliage. Regularly inspect your plants for signs of thrip damage and consider applying an insecticidal soap spray if necessary.
  3. Fungal Diseases: Moisture-loving fungal diseases like downy mildew and pink root can pose a threat to onion crops in Missouri’s humid climate. To prevent these diseases, practice crop rotation, avoid overhead watering, and ensure good air circulation around the plants.

Tips for managing temperature fluctuations and extreme weather conditions

Missouri experiences significant temperature fluctuations throughout the year. Here are some tips to help your onion plants withstand these changes:

  1. Mulching: Apply a layer of organic mulch around your onion plants to regulate soil temperature and retain moisture. This helps protect them during both hot summers and cold winters.
  2. Watering: Onions require consistent moisture, especially during their early growth stages. Water deeply but infrequently to encourage deep root development. During dry spells, provide supplemental irrigation to keep the soil consistently moist.
  3. Protective Covers: Consider using protective covers like cloches or row covers to shield young onion plants from late spring frosts or early fall freezes.

Recommendations for selecting onion varieties resistant to local challenges

Choosing the right onion varieties can make a significant difference in your success as a Missouri gardener. Look for varieties that are known to thrive in the region’s specific conditions:

  • Yellow Onions


In conclusion, planting onions in Missouri requires careful consideration of the right timing, techniques, and practices. By following the best practices outlined above, you can increase your chances of a successful onion harvest.

To recap, it is crucial to plant onions at the right time in Missouri. The planting calendar provided can serve as a helpful guide to ensure you sow your seeds or transplant your seedlings at the appropriate times. Starting onion seeds indoors can give your plants a head start before transferring them outdoors.

There are various tips and techniques that can enhance their growth. From proper spacing and soil preparation to adequate watering and fertilization, paying attention to these details will contribute to healthy onion plants. Harvesting and curing onions correctly is equally important for preserving their quality and flavor.

It’s worth noting that there are some special considerations when planting onions in Missouri. Factors such as climate conditions, local pests, and diseases should be taken into account. By staying informed about these aspects specific to your region, you can address any challenges effectively.

To further expand your knowledge on successfully growing onions in Missouri, consider seeking additional resources from reputable gardening experts or organizations. Their expertise can provide valuable insights tailored specifically for your area.

Remember that practice makes perfect. Don’t be discouraged by initial setbacks; instead, learn from them and keep improving your skills over time.

Happy onion planting!


Q: How deep should I plant onion sets?

A: Onion sets should be planted approximately 1 inch deep in the soil.

Q: Can I grow onions from kitchen scraps?

A: While it is possible to regrow green onions from kitchen scraps by placing their roots in water or soil, this method may not yield full-sized bulbs like those grown from seed or sets.

Q: Do I need to water my onion plants regularly?

A: Onions require consistent moisture, especially during dry periods. Regular watering is essential to ensure their healthy growth.

Q: How long does it take for onions to mature?

A: Onions typically take around 90 to 120 days from planting to reach maturity, depending on the variety.

Q: Can I grow onions in containers?

A: Yes, onions can be grown successfully in containers as long as the container provides enough depth for root development and proper drainage.

Q: What are some common pests that affect onion plants in Missouri?

A: Common pests that may affect onion plants in Missouri include onion maggots, thrips, and nematodes. Taking preventive measures such as using row covers or applying organic pest control methods can help mitigate these issues.