The Ultimate Guide to Growing Onions: From Seed to Harvest

Dried or fresh, raw or cooked, onions are one of the most versatile vegetables in the kitchen. From soups and salads to breads and casseroles, they add flavor and depth to countless dishes.

Onions

What many gardeners don’t realize is that onions are surprisingly easy to grow—even in small spaces! Whether you have a garden bed or just a few spare corners, onions can thrive with minimal effort.

🧅 Types of Onions

Onions come in a wide range of shapes, sizes, and colors—from small white pickling onions to large red or yellow Spanish varieties. Each type has its own growth habit and flavor profile.

Common Varieties

• Scallions (Green Onions): These can be harvested young from most onion types. For a continual supply, try perennial bunching onions (Allium fistulosum)—they’re nearly pest- and disease-proof.

• Multiplier or Potato Onions (A. cepa Aggregatum group): Each bulb multiplies into a cluster, giving you fresh bulbs to replant every season.

• Egyptian or Top Onions (A. cepa Proliferum group): Known for forming small bulb clusters on the tips of their stems—truly unique and ornamental!

• Chives (A. schoenoprasum) and Garlic Chives (A. tuberosum): These onion relatives are perfect for borders or containers and are prized for their mild flavor.

• Shallots (A. cepa Aggregatum group): Beloved by chefs for their delicate, sweet flavor.

🌿 How to Plant Onions

You can grow onions from seeds, transplants, or sets, each with its pros and cons:

1. Transplants

• Sold in bunches and ready to plant.

• Mature quickly (in about 65 days).

• Limited variety and more disease-prone.

2. Sets

• Small, immature bulbs from the previous year.

• Easiest and fastest to grow—perfect for beginners.

• Choose small sets (½ inch wide) to prevent premature flowering or “bolting.”

• One pound of seed plants about 50 feet of row.

3. Seeds

• Offer the widest choice of cultivars.

• Requires patience: up to 4 months to mature.

• Best started indoors in cold climates (4–6 weeks before the last frost).

🌞 Daylength Matters

• Short-day onions (like ‘Red Hamburger’) form bulbs when days reach 10–12 hours—ideal for southern regions.

• Long-day onions (like ‘Sweet Sandwich’ and ‘Southport Red Globe’) need 13–16 hours of sunlight—best for northern climates.

🌱 Planting Tips

• Sow seeds ½ inch deep in rows, thinning seedlings to 6 inches apart.

• Transplants or sets should be spaced 4–6 inches apart.

• Mix in radish seeds to mark rows and distract root maggots.

• Onions prefer cool weather for leaf growth and warmer temperatures for bulb formation.

Onion bulbs

🌻 Growing Onions Successfully

• Keep the bed weed-free. Onions have shallow roots and can’t compete well with weeds. Use a hoe to slice weeds rather than pulling them.

• Mulch after the soil warms up to retain moisture and discourage weeds.

• Water consistently—about 1 inch per week. Dry conditions can cause bulbs to split.

• Avoid excess nitrogen fertilizers, which promote leafy growth at the expense of bulbs.

• When new center growth stops, bulbs are forming—reduce watering slightly.

🧄 Growing Onion Relatives

🧅 Egyptian Onions

• Plant in the fall and harvest green in the spring.

• Small bulb clusters form at the top of stems in summer—harvest these for replanting or fresh use.

🌸 Chives and Garlic Chives

• Plant in early spring in fertile soil with full sun.

• Divide clumps every 3 years for vigorous growth.

• Trim tops regularly and remove spent flowers to prevent self-seeding.

• Grow indoors in winter for fresh greens year-round.

🧅 Shallots

• Plant cloves 1 inch deep and 2–3 inches apart in early spring.

• Don’t over-fertilize; just keep the soil moist and loose.

• Harvest bulbs in about 5 months—or cut tops as green onions to encourage more bulbs.

💧 Watering Tips

Efficient watering keeps onions healthy:

• Use soaker hoses along rows to deliver water directly to roots.

• Alternatively, dig a shallow irrigation trench between rows and fill with water—this keeps the soil surface dry and reduces weeds.

🐛 Common Onion Problems & Solutions

Pests

• Onion maggots: Scatter onions throughout your garden instead of one large patch. Add a thin sand layer around bulbs to deter egg-laying.

• Thrips: Tiny insects that cause silver streaks on leaves. Prevent by keeping the garden weed-free and using reflective mulch.

  • Control naturally with spinosad or neem oil if infestation worsens.

Diseases

• Smut, downy mildew, pink root, and neck rot are fungal diseases that thrive in wet or compacted soil.

  • Prevent by rotating crops annually.

  • Improve drainage with compost or organic matter.

🧺 Harvesting & Storing Onions

1. When the tops turn yellow, gently bend them over with a rake.

2. After the tops brown, pull or dig bulbs on a sunny day.

3. Dry them in the sun for several days—cover bulbs with neighboring tops to prevent sunburn.

4. Once dry, remove soil and trim tops (or braid them).

5. Store in a cool, dry, and airy place—mesh bags or braided bunches work best.

✅ Properly dried onions can last 4 months to a full year!

🌾 Final Thoughts

Growing onions at home is easy and rewarding and adds flavor to your meals year-round. With just a bit of planning and care, you can harvest fresh, flavorful bulbs—and even keep them going season after season with perennial varieties.

So, whether you’re a beginner or a seasoned gardener, onions deserve a spot in your garden. They’re low-maintenance, space-efficient, and endlessly useful—a true garden essential.