It’s a waste of tears crying over the bland, flavorless onions from the grocery store when growing your own bold, pungent bulbs is so simple. Homegrown onions offer a wide variety of flavors and textures and are a staple in dishes from every corner of the world.
From soups and stir-fries to sauces and salads, your meals will never be the same once you experience the difference of fresh, garden-grown onions. They’re easy to grow, simple to store, and compact enough to tuck into garden borders or flower beds for a bonus harvest.
Whether you choose to grow from seed or from starts, onions reward your effort with big flavor and dependable harvests. Here’s everything you need to know to start growing onions at home.
When and Where Should You Plant Onions?
Onions thrive in full sun and fertile, well-drained soil. They prefer cooler weather during their early growth stages, so plant them in early spring. This gives them time to grow healthy green tops before the weather warms and the bulbs begin to form.
Onions form bulbs in response to day length, so it’s important to choose the right type for your region:
- Long-Day Onions (e.g., ‘Sweet Spanish’) need 14–16 hours of daylight and are best for northern areas.
- Short-Day Onions (e.g., ‘Bermuda’) only require 10–12 hours and are ideal for southern gardeners.
- Intermediate-Day Onions are perfect for gardeners in between.
Growing Onions: Seeds vs. Transplants vs. Sets
There are three main ways to grow onions, and each has pros and cons:
1. Growing Onions from Seeds
Seeds offer the greatest variety and are the most affordable option. However, they require the longest growing season—often 110+ days.
- Start indoors 8–12 weeks before your last frost date. Keep temps around 60°F.
- Trim tops regularly to encourage sturdy growth (bonus: the trimmings are delicious in salads).
- Direct sow outdoors 3–4 weeks before your last frost. Sow thickly in rows, then thin seedlings after sprouting.
Pro Tip: Mix in fast-sprouting radish seeds to help mark your rows.
2. Growing Onions from Transplants
Transplants are live seedlings that give you a head start in the growing season. They’re usually sold in bundles and are several weeks old.
- Easier than starting from seed
- More variety than sets
- Slightly more susceptible to disease
3. Growing Onions from Sets
Sets are small, dormant bulbs grown the previous year. They’re the easiest and quickest way to grow onions, especially for beginners.
- Plant sets 1 inch deep and 3 inches apart.
- Harvest early for green onions or let them mature for full-sized bulbs.
- Fewer variety options and more prone to bolting.
Prepping Your Onion Bed
Onions prefer loose, fertile, and well-drained soil. Avoid heavy clay unless amended with compost or sand. A slightly acidic soil (pH 6.2–6.8) works best.
Before planting, dig 6 inches deep and mix in a 1-inch layer of compost. This gives your onions the nutrients they need for healthy bulb development.
Watering, Mulching & Feeding Your Onions
- Water: Onions need consistent moisture, especially during bulb formation. Aim for 1 inch of water per week.
- Mulch: Once seedlings are established, mulch helps suppress weeds and retain moisture.
- Fertilizer: If you amended your bed well, you may not need to fertilize. But for larger bulbs, apply a nitrogen-rich fertilizer every few weeks early in the growing season.
Companion Planting and Crop Rotation
Onions make excellent garden neighbors. Try planting them near:
- Carrots
- Beets
- Lettuce
- Tomatoes
- Chamomile (said to improve flavor)
Avoid planting onions near peas and asparagus, which may stunt their growth. And don’t forget to rotate your onion beds each year to avoid soil-borne diseases and pests.
Common Onion Pests and Problems
While onions are relatively hardy, keep an eye out for these potential issues:
- Gophers & Rodents: Love onion bulbs. Use traps or fencing to protect your crop.
- Onion Thrips: Tiny pests that damage leaves. Overhead watering and beneficial insects like lacewings can help.
- Onion Maggots: Larvae that feed on roots. Rotate crops annually to reduce risk.
- Downy Mildew: A fungal disease that thrives in damp, crowded conditions. Improve air circulation and spacing to prevent it.
Harvesting and Storing Onions
Your onions are ready to harvest when their tops turn yellow and fall over. Gently bend over any remaining upright greens to signal the bulbs to finish maturing. After a few days, carefully dig them up.
Curing your onions is key for long-term storage:
- Lay them out in a single layer in a warm, dry place with good airflow.
- Cover the tops of some onions with others to prevent sunburn.
- Once the outer skins are papery, trim the tops and roots.
- Store in a cool, dry, dark place. Properly cured onions can last 4–12 months.
Tip: Any bruised onions won’t store well—chop and freeze them for winter use.
Saving Onion Seeds
Want to save seeds? Since onions are biennial, you’ll need to let them grow a second year:
- Store the best bulbs for 3–6 months.
- Replant in spring to let them flower.
- Once the seed heads dry, harvest and store the seeds in a paper bag in a cool, dry place.
Choosing the Best Onion Variety
Your ideal onion depends on:
- Day length in your region
- Storage goals
- Flavor preferences
Popular Onion Types:
- Yellow Onions: All-purpose with a balance of sweet and pungent flavors. Great for cooking.
- White Onions: Sharper flavor, more tender—perfect in salsas.
- Sweet Onions (e.g., Vidalia): Mild and delicious raw in salads or sandwiches.
- Red Onions: Milder and colorful, often eaten raw.
- Egyptian Walking Onions: Perennial onions that produce small bulb clusters at the top of their stems. Great for cut-and-come-again harvests.
Extra Tips for a Thriving Onion Patch
- Keep weeds at bay. Onions don’t like competition.
- Water consistently. Uneven watering can cause bulbs to split.
- Start early. Many onions need over 100 days to mature, so early planting is essential.
Growing your own onions is one of the most rewarding garden projects. Whether you’re a beginner or a seasoned grower, these hardy bulbs offer high yield, big flavor, and months of delicious storage. Plus, nothing beats the satisfaction of pulling a perfectly cured onion from your pantry in the middle of winter and knowing you grew it yourself.