When To Plant Onions In Missouri

The best time to plant onions in Missouri is in the spring, after the last frost has passed. You will need to start them indoors about six weeks before you plan to transplant them outside.

If you’re looking to add some flavor to your home-cooked meals, there’s no need to look any further than the onion. This versatile vegetable can be used in a variety of dishes, and it’s easy to grow your own onions at home. But when is the best time to plant onions in Missouri?

When To Plant Onions In Missouri

Sow onion seeds ¼ to ½ inch deep, in rows 12 to 18 inches apart. Thin plants so they are 4 to 6 inches apart in the row when they are 3 to 4 inches tall. When grown from transplants, space plants 6 to 8 inches apart in the row.

To get large onion bulbs, add nitrogen fertilizer when you prepare the bed and again when the plants are 6 to 8 weeks old. Apply a total of 1 pound of actual nitrogen per 100 feet of row.

When To Plant Onions In Missouri

When Is The Best Time To Plant Onions In Missouri?

Onions are a cool-season crop that can be planted as early as February in Missouri. Set the onion plants out in the garden in early to mid-April, spacing them about 6 inches apart in rows that are 12 inches apart.

What Type Of Onion Is Best For Missouri

Onions (Allium cepa L.) are grown in Missouri as annual crops and are bestStart onions from sets, transplants, or seeds. Sets are small onions that were grown the previous year and dormant over winter. Expect poor germination and variable results with sets. They are getting harder to find each year as more growers plant transplants or seed.

If you grow your own transplants, sow seeds indoors in late February to early March on heat mats set at 70°F to 75°F under fluorescent light for 14 to 16 hours daily. Keep the soil moist but not wet, and transplant when the onion plants are 3 to 4 inches tall into prepared outdoor beds after all danger of frost has passed.

You can direct seed onions outdoors in Missouri if you wait until mid-March to early April when the soil temperature has reached at least 60°F for 3 days in a row. Place seeds ¼ to ½ inch deep in well-prepared soil, and thin plants when they are 4 inches tall to one per foot in the row.

How To Prepare The Soil For Planting Onions 

Onions are fuss-free to grow and a marvelous crop to have in the kitchen garden. They are one of the first crops that can be planted in spring and, if you have the space, you can successively plant more to crop right through summer and autumn. They are suited to growing in most soil types but prefer a well-drained soil that is high in organic matter.

To prepare the soil for planting onions, dig over the area you intend to use and remove any large stones or debris. If your soil is particularly heavy, you may want to consider adding some horticultural grit or sand to improve drainage. Once the area is clear, dig a trench around 15cm (6in) deep and wide enough to comfortably fit your plants.

Space your plants at least 15cm (6in) apart, with 30cm (12in) between rows. If you are growing large onions such as ‘Excel’ or ‘Sturon’, you will need to space them 20-30cm (8-12in) apart. You can plant your onions closer together if you intend to harvest them as ‘spring onions’.

Once planted, water well and keep the area free from weeds by regularly hoeing. Mulching around your onions with straw or grass clippings will help suppress weeds and retain moisture in the soil.

How To Plant Onion Sets In Missouri

Onion sets are small, immature onions that are planted in the spring to produce a full-sized onion in late summer. They are planted in the same way as seed onions, but they do not need to be started early indoors since they are already mature enough to plant directly in the garden.

If you live in an area with a long growing season, you can plant onion sets as early as February. In most of Missouri, however, it is best to wait until March or April to plant them. Onions do best when they are grown in full sun, in well-drained soil that has been amended with plenty of organic matter.

To plant onion sets, simply push them 1-2 inches into the soil, making sure that the pointed end is facing up. Space them 4-6 inches apart, and water them well. Thin out the seedlings once they have grown to be 3-4 inches tall, so that they are spaced 6-8 inches apart.

Once your onion plants start to form bulbs, you can add a layer of mulch around them to help keep the soil moist and prevent weeds from competing for moisture and nutrients. Stop watering your onions about 2 weeks before you plan to harvest them, so that their bulbs will have time to cure and develop their full flavor.

When To Plant Onions In Missouri

How To Care For Onion Plants In Missouri

Onions are a kitchen staple and can be grown in Missouri from sets, transplants or seeds. They’re a cool-season crop, so they can be one of the first vegetables planted in the spring, as soon as the soil can be worked. They’re also one of the last crops to be harvested in the fall.

To get a jump on the growing season, plant onion sets (dried, immature onion bulbs) in early March. Sets are available at most garden stores. If you start with sets, plant them about 2 inches deep and 4 inches apart in rows that are 18 to 24 inches apart.

If you start from seed, sow the seeds indoors in late winter and transplant the seedlings to the garden when they’re 4 to 6 weeks old. Plant them about 1/2 inch deep and 2 inches apart in rows that are 18 to 24 inches apart.

Onions can also be direct-seeded in the garden after all danger of frost has passed and the soil has warmed up. Sow seeds 1/2 inch deep and 2 inches apart in rows that are 18 to 24 inches apart; thin to 4-inch spacing when seedlings are 4 weeks old.

All onions need full sun and well-drained soil with a pH of 6 to 7 for best growth. Fertilize with 1/2 pound of actual nitrogen per 100 square feet of bed space before planting; side-dress plants with an additional 1/4 pound of nitrogen per 100 square feet when they’re about 6 weeks old for bulb development. Keep plants evenly watered throughout their growing season for best results; too much or too little water at any time during production can affect bulb size and quality negatively.

When To Harvest Onions In Missouri

Onions are a cool-weather crop that is usually planted in the early spring, as soon as the ground can be worked. In Missouri, this is typically between late February and early April. The onions will mature and be ready to harvest 90 to 120 days after planting, depending on the variety. 

You will know when your onions are ready to harvest when the tops begin to fall over and turn yellow or brown. At this point, stop watering the onions so that they will begin to form bulbs. Once the tops are completely brown and dried out, pull the onions from the ground and allow them to cure in a warm, dry place for two to three weeks. 

After they have cured, trim off the roots and tops, brush off any dirt and store in a cool, dark place. Properly cured and stored onion can last up to six months.

When To Plant Onions In Missouri

Storing Onions From Missouri

Onions can be kept in a cool, dark place for several months. An ideal storage temperature for onions is between 32 and 40 degrees F. Store onions in a mesh bag or ventilated container to allow air circulation. Do not store onions with potatoes because they will cause the potatoes to sprout. Place the bag of onions in the refrigerator if your kitchen is too warm. Missourians typically plant onion sets (small onion bulbs) in February or early March. Work the soil to a depth of 8 inches before planting using a spading fork or rototiller. Rake the area smooth.

Recipes Featuring Missouri Onions

Onions are a staple ingredient in many recipes, and they can be used in so many different ways. Here are some recipes that feature Missouri onions.

Roasted Missouri onion and bacon quiche


1 unbaked 9-inch pie crust

1/2 pound bacon, diced

1/2 cup chopped Missouri onion

3 eggs, beaten

1 cup milk

1/2 cup shredded cheddar cheese


1. Preheat the oven to 350 degrees Fahrenheit.

2. In a skillet, cook the bacon over medium heat until crisp. Remove with a slotted spoon and set aside on paper towels to cool.

3. In the same skillet, sauté the chopped onion in the bacon grease until softened.

4. In a large bowl, whisk together the eggs and milk. Stir in the bacon, onion, and cheese. Pour into the prepared pie crust.

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