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Planting onions in fall is one of the many joys of a seasonal gardening routine.

As the temperatures drop and the leaves begin to turn, I find it the perfect time to get onions into the ground.

Planting onions in fall gives them a head start to establish roots over the winter, leading to a robust and earlier harvest in the spring.

Here I’ll share my experiences and tips to help you enjoy the benefits of fall onion planting as much as I do.

To learn more about growing onions, check out my guide:

Onion Companion Plants: Creating a Natural Ecosystem

Choosing the Right Onion Varieties

Selecting the right onion varieties for fall planting is a crucial step that can significantly impact your harvest.

Over the years, I've discovered that understanding the different types of onions and how they respond to daylight and temperature makes all the difference.

Understanding Day Length and Onion Types

Onions are categorized based on their response to day length, which affects bulb formation:

Short-Day Onions:
These onions begin forming bulbs when daylight reaches 10-12 hours.
They're ideal for regions with mild winters and are typically planted in the fall for a spring harvest.
However, in cooler climates, they may not perform as well.
Intermediate-Day Onions:
Also known as day-neutral onions, they require 12-14 hours of daylight.
They're versatile and can adapt to a range of climates, making them a safe choice for many gardens.
Long-Day Onions:
These varieties need 14-16 hours of daylight to start bulb formation.
They're best suited for northern regions with long summer days.
Long-day onions are excellent for fall planting in cooler climates, as they establish roots over winter and grow vigorously in spring.

My Top Picks for Fall Planting

Here are the onion varieties that I recommend:

Walla Walla:

A sweet, mild onion that's perfect for fresh eating.

It's hardy enough to withstand colder temperatures, making it a reliable choice for fall planting.

Red Onions:

Varieties like 'Red Baron' or 'Red Wing' add color and flavor to dishes.

They store well and have a slightly sharper taste, which I particularly enjoy in salads.

Factors to Consider When Choosing Varieties

Climate Suitability:
Make sure the onion variety you choose is appropriate for your local climate and winter conditions.
Disease Resistance:
Opt for varieties that are resistant to common onion diseases.
This can reduce the need for chemical interventions and lead to a healthier crop.
Purpose of Harvest:
Consider whether you want onions for fresh consumption, cooking, or long-term storage.
Some varieties are better suited for certain uses than others.

Sourcing Quality Seeds or Sets

I recommend starting with high-quality onion sets or seeds from reputable suppliers.

For fall planting, sets are often more convenient, as they've already gone through one growth cycle and can establish themselves more quickly in the garden.

Onion Sets:

These are small, immature onion bulbs that are easy to plant and have a high success rate.

Look for firm, disease-free sets.

Here is the set I recommend:

Seeds:

If you prefer starting from seeds, sow them indoors in late summer and transplant them into the garden in early fall.

This method allows you to choose from a wider range of varieties.

Timing Your Planting

Planting at the right time ensures that onions develop strong root systems before the ground freezes:

Zones 5 and Colder:
Aim to plant onion sets in late August or early September.
Zones 6 and Warmer:
You can plant a bit later, even into October, depending on local weather patterns.

For more fall planting tips, check out my guide:

The 10 Best Autumn Bedding Plants

basket of harvested onions planted in the fall

Preparing the Soil

Getting the soil just right is a crucial step when you’re getting ready to plant onions in the fall.

Onions prefer fertile, well-drained soil with a neutral to slightly acidic pH.

Here's how to prepare your garden to give your onions the best start possible.

Testing and Understanding Soil pH

Before you do anything else, test the soil's pH level.

Onions thrive in soil with a pH between 6.0 and 7.0.

You can use a simple home testing kit.

Knowing the pH helps you decide if you need to adjust the soil to create optimal growing conditions.

Here is the pH testing kit I recommend:

Clearing and Loosening the Soil

Start by clearing the garden bed of any weeds, rocks, or debris.

Weeds compete with onions for nutrients, so it's important to remove them thoroughly.

Then, loosen the soil to a depth of about 8 to 10 inches using a garden fork or tiller.

Loosening the soil improves aeration and allows the onion roots to penetrate more easily.

This garden fork is perfect for the job:

Enriching with Organic Matter

Adding organic matter is key to boosting soil fertility.

I mix in well-rotted compost or manure to provide essential nutrients.

Spreading a 2- to 3-inch layer over the soil and working it in helps improve soil structure and moisture retention.

This organic boost gives the onions the nutrients they need to grow strong.

If you don’t have well-rotted manure or homemade compost, here is the bagged compost I recommend using:

Ensuring Good Drainage

Onions don't like wet feet, so ensuring proper drainage is essential.

If your soil is heavy clay like mine, you might consider creating raised beds or incorporating sand to improve drainage.

I recommend building up the soil into slight mounds or rows to prevent water from pooling around the bulbs.

Adjusting Soil pH and Nutrients

If the soil test shows that the pH is too low (too acidic), add garden lime to raise it.

If it's too high (too alkaline), elemental sulfur can help lower the pH.

I also recommend sprinkling a balanced fertilizer rich in phosphorus to promote root development.

Here is the fertilizer I recommend:

Final Soil Preparation Steps

After amending the soil, rake it smooth to remove any large clumps.

This creates an even surface that's easy to work with when planting onion sets.

At this point, the soil is ready, and you can feel confident that it's primed to support healthy growth throughout the winter and into spring.

For more tips, check out my guides:

What to Put on the Bottom of a Raised Garden Bed

The Best Gifts for Gardeners

red onions growing garden bed after fall planting

Planting Onion Sets

Planting onion sets in the fall is a straightforward process that sets the foundation for a successful harvest next year.

Choosing the Right Time to Plant

Timing is crucial when planting onion sets.

Aim to plant them in late August or early September.

This gives the onions enough time to establish their root systems before the colder temperatures set in.

If you live in a warmer climate, you might have a slightly different timeframe, so it's worth checking with your local gardening resources.

Selecting Quality Onion Sets

When I'm at the garden center or browsing online, I look for onion sets that are:

Firm and Dry:
Avoid any that feel soft or show signs of mold.
Uniform in Size:
Smaller sets, about the size of a marble, tend to develop into stronger plants.
Suitable Varieties:
As mentioned earlier, day onions like Walla Walla or certain red onions are excellent choices for fall planting.

Planting Steps

Here's how to plant onion sets:

Mark the Rows:
Use stakes and string to mark straight rows, spacing them about 12 inches apart for easy access.
Set Spacing:
Within the rows, plant the onion sets 4-6 inches apart.
This spacing allows enough room for the bulbs to grow without crowding.
Planting Depth:
Each onion set is placed about 1 inch deep, with the pointed end facing upwards.
Gently press them into the soil but avoid burying them too deep.
Covering the Sets:
Lightly cover the sets with soil, ensuring the tips are just beneath the surface.

Watering After Planting

Once all the sets are in the ground, water the area thoroughly.

The initial watering helps settle the soil around the sets and kick-starts root development.

After this, monitor the soil moisture, keeping it slightly damp but not waterlogged.

For more watering tips, check out my guide on how to use watering globes.

Mulching for Winter Protection

To help the onion sets survive the winter, apply a layer of mulch:

Materials Used:
Straw, shredded leaves, or grass clippings work well.
Application Depth:
A 2- to 3-inch layer provides insulation against temperature fluctuations.
Benefits:
Mulch conserves moisture, suppresses weeds, and protects the onions from harsh conditions.
Here is the mulch I recommend:

Labeling and Record-Keeping

I find it helpful to label the varieties I've planted, especially if I'm trying out new ones.

Keeping a garden journal with notes on planting dates and conditions can be valuable for future reference.

Here is the journal I recommend:

Post-Planting Care

In the weeks following planting:

Check for Disturbances:
Occasionally check to make sure animals haven't dug up any sets.
Avoid Overwatering:
Since the weather can be cooler and wetter in the fall, make sure not to overwater, which can lead to rot.
Prepare for Spring:
Knowing that the groundwork is laid, I look forward to the onions sprouting when the weather warms up.

For more fall planting tips, check out my guides:

Bulb Lasagne in 4 Easy Steps

The Top 3 Bulbs that Flower in Winter

onions planted in fall for a spring harvest

Caring for Onions Over Winter

After planting my onion sets in the fall, ensuring they survive and thrive through the winter months is essential.

While onions are quite hardy, there are several steps you can take to protect them from harsh weather and set the stage for a successful spring growth.

Protecting Against Severe Cold

In areas where temperatures drop significantly, additional protection might be necessary.

Row Covers:

Using floating row covers or cold frames can shield the onions from extreme cold and wind.

Here is the row cover I recommend:

Snow as Insulation:

Interestingly, a layer of snow can act as natural insulation.

Avoid removing snow from the onion bed unless it's excessively heavy.

Checking for Pest and Disease Issues

Even in winter, it's possible for pests or diseases to affect onions.

Pest Monitoring:
Occasionally inspect the area for signs of rodents or other pests that might dig up the sets.
Disease Prevention:
Good drainage and proper spacing reduce the risk of fungal diseases.

Minimal Disturbance

One of the advantages of fall-planted onions is that they require little intervention during winter.

Avoid Walking on Beds:
Try not to compact the soil by stepping on the beds, especially when the ground is wet or frozen.
Leave Them Be:
Aside from periodic checks, let the onions rest and focus on other garden planning tasks.

Preparing for Spring Growth

As winter progresses toward spring, start preparing for the active growing season.

Gradual Mulch Removal:
When the risk of severe frost has passed, gradually remove some of the mulch to allow the soil to warm up and the onions to access more sunlight.
Fertilizing:
In early spring, apply a light feeding of nitrogen-rich fertilizer to support leaf growth.
Here is the fertilizer I recommend:

For more autumn planting tips, check out my guides:

Secrets to Successfully Planting Allium Bulbs

Container Color: Easy Steps to Growing Bulbs in Pots

Quick FAQs

1. Can I plant onions in the fall?

Absolutely! Planting onions in the fall allows them to establish roots over the winter, leading to a potentially earlier and larger harvest in the spring.

2. What are onion sets for fall planting?

Onion sets are small, immature onion bulbs that are ideal for planting in the fall.

They have a higher success rate compared to seeds when overwintering.

3. How do I plant winter onions?

Plant winter onions by placing the sets about an inch deep into well-prepared soil.

Space them adequately and cover with mulch to protect against cold temperatures.

4. How late can you plant onions in the fall?

You can plant onion sets until the ground begins to freeze.

However, earlier planting gives the onions more time to develop strong root systems.

5. Why are my onion seedlings falling over?

Onion seedlings may fall over due to factors like inadequate light, overwatering, or nutrient deficiencies.

Ensure they receive sufficient sunlight and balanced watering.

6. When should I plant onion sets in the spring?

For spring planting, plant onion sets as soon as the soil is workable, usually in March or April, depending on your local climate.

For more inspiration, check out my guide:

Top 10 Flowers to Plant in Your Vegetable Garden

Wrap-Up

Planting onions in the fall is such a great gardening tradition each year.

Watching the planted onions settle in over winter and seeing the onions growing vigorously come spring is a wonderful thing.

Choosing the right day varieties and giving them a good start will definitely result in a bountiful onion crop.

There's nothing quite like harvesting onions that you've nurtured throughout the seasons.

If you're passionate about growing onions, I encourage you to give fall planting a try—it's a rewarding experience that pays off with a delicious harvest.