If you’ve ever dreamed of growing your own crisp, flavorful onions at home, you’ll be pleased to know it’s easier than you might think. Onions are one of the most rewarding and versatile vegetables you can grow, and with a little planning and care, you can enjoy a bountiful harvest right from your backyard or garden bed.
In this comprehensive guide, we’ll walk you through everything you need to know about how to plant and grow onions for a full harvest — from choosing the right variety to harvesting and storing your homegrown onions.
Why Grow Your Own Onions?
Onions are a kitchen staple, essential for countless recipes. Growing your own offers several benefits:
- Fresher and better flavor than store-bought onions
- Variety selection — you can grow types you won’t find in supermarkets
- Saves money over time
- Relatively low-maintenance once established
- Great for beginners and seasoned gardeners alike
Plus, onions are pest-resistant and don’t require much space, making them ideal for raised beds, garden plots, or even containers.
Understanding Onion Types
Before planting, it’s important to know the different types of onions, as this will affect when and how you plant them.
1. Short-Day Onions
- Need 10–12 hours of daylight to form bulbs
- Best for southern, warmer climates (USDA zones 7 and up)
- Plant in fall or winter for spring harvest
- Examples: Texas Sweet, Yellow Granex, Red Creole
2. Long-Day Onions
- Need 14–16 hours of daylight to bulb
- Ideal for northern regions (USDA zones 6 and below)
- Plant in early spring for midsummer harvest
- Examples: Walla Walla, Yellow Sweet Spanish, Red Zeppelin
3. Day-Neutral Onions
- Bulb with 12–14 hours of daylight
- Adaptable to most climates
- Examples: Candy, Red Candy Apple, Super Star
Best Ways to Grow Onions
There are three main ways to start onions:
1. From Seeds
- Cheapest option
- Takes longer (start seeds indoors 8–12 weeks before your last frost date)
2. From Sets
- Small, immature onion bulbs
- Easy and fast; ideal for beginners
- Available at most garden centers
3. From Transplants
- Young, nursery-grown onion plants
- Reliable for quicker harvests
Pro Tip: Beginners should start with onion sets or transplants for better success rates.
When to Plant Onions
Timing depends on your climate and the onion variety:
- Long-Day Onions: Plant outdoors as soon as the soil is workable in early spring.
- Short-Day Onions: Plant in late fall or winter in mild climates.
- Day-Neutral Onions: Plant in early spring in most regions.
Soil temperature should be at least 50°F (10°C) for planting.
How to Plant Onions: Step-by-Step
Step 1: Prepare the Soil
Onions prefer:
- Loamy, well-draining soil
- pH of 6.0–7.0
- Rich in organic matter
Work compost or aged manure into the soil a few weeks before planting. Avoid heavy, clay soils that retain water.
Step 2: Space and Plant the Onions
- Onion Sets or Transplants: Space 4–6 inches apart in rows 12–18 inches apart.
- Onion Seeds: Sow ½ inch deep, thinning seedlings to 4–6 inches apart later.
Plant sets with the pointed end up and the flat root end down, covering with about 1 inch of soil.
Caring for Onion Plants
1. Watering
Onions have shallow roots and need consistent moisture.
- Water 1 inch per week or more during dry spells.
- Avoid waterlogged soil, which can cause rot.
Tip: Mulch around plants to conserve moisture and control weeds.
2. Fertilizing
Onions are heavy feeders.
- Apply a balanced fertilizer (10-10-10) before planting.
- Once shoots appear, side-dress with nitrogen-rich fertilizer (21-0-0) every 3–4 weeks.
- Stop fertilizing once bulbs start forming.
3. Weeding
Keep onion beds weed-free, as weeds compete for nutrients and water.
Hand-pull weeds carefully to avoid damaging the shallow onion roots.
4. Pest and Disease Control
Onions are relatively hardy but can suffer from:
- Onion maggots: Use floating row covers.
- Thrips: Spray with insecticidal soap.
- Fungal diseases: Ensure good air circulation and avoid overhead watering.
How to Know When Onions Are Ready to Harvest
Onions are typically ready to harvest 100–120 days after planting from seeds or 60–80 days from sets.
Signs to look for:
- Bulbs are large and poke through the soil
- Leaves start to yellow and fall over naturally
Pro Tip: Stop watering when most of the tops fall over. This helps the bulbs cure properly.
How to Harvest Onions
- Loosen the soil around the bulbs with a fork.
- Gently pull up the onions by hand.
- Lay them out to dry in a shaded, airy location for 7–14 days until the necks are completely dry.
Important: Avoid bruising or damaging bulbs during harvest.
Storing Onions for Maximum Freshness
Once cured:
- Remove excess dirt and trim roots.
- Cut tops to about 1 inch above the bulb.
- Store in a cool, dry, and well-ventilated area.
Storage tips:
- Keep onions in mesh bags, baskets, or pantyhose.
- Do not store onions near potatoes, as they release moisture and gases that cause spoilage.
Storage life:
- Sweet varieties: 1–2 months
- Storage onions (Yellow or Red Zeppelin): 6–12 months
Bonus: Growing Green Onions (Scallions)
Green onions, or scallions, are quick and easy:
- Plant onion sets or seeds 1 inch apart.
- Harvest once shoots reach 6–8 inches tall.
- Cut at the base and leave roots in the soil for regrowth.
You can also regrow green onions indoors in water by placing cut bases in a glass on a sunny windowsill.
Common Onion Growing Problems (and How to Fix Them)
| Problem | Cause | Solution |
|---|---|---|
| Small bulbs | Crowding, not enough light, poor soil | Thin plants, ensure full sun, enrich soil |
| Bulb rot | Overwatering, poor drainage | Improve soil drainage, water less |
| Bolting (flowering) | Heat stress, fluctuating weather | Use bolt-resistant varieties, plant early |
| Yellow leaves | Nutrient deficiency or thrips | Fertilize, treat pests with insecticidal soap |
Final Thoughts
Learning how to plant and grow onions for a full harvest is a rewarding and practical gardening project. Whether you grow from seeds, sets, or transplants, onions require relatively little space, modest care, and are incredibly versatile in the kitchen.
By choosing the right variety for your region, preparing nutrient-rich soil, and keeping up with watering and weeding, you’ll be well on your way to harvesting beautiful, flavorful onions to enjoy for months.
So why not grab a handful of onion sets and start your own harvest today? Your future soups, salads, and salsas will thank you!
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