Few vegetables are as satisfying to pull from the soil as onions. Straight out of the garden, they’re crisp, sweet, and full of flavor—not to mention rich in vitamin C. Best of all, they’re a versatile crop that, with a little know-how, can thrive in home gardens across the U.S.
While onions are fairly easy to grow, success depends on two main things: choosing the right day-length variety for your location and providing consistent care throughout the growing season.
In my 20+ years as a Master Gardener in Texas, I’ve seen bumper harvests and total flops—and almost always, the difference comes down to variety choice and timing. Let’s dig in.
1. Choosing the Right Day-Length Variety
Onions initiate bulb formation based on day length—the amount of daylight they receive. If you plant the wrong type for your latitude, you’ll get lots of green leaves but disappointingly small bulbs.
- Long-Day Onions – Need 14–16 hours of daylight. Ideal for the northern U.S. (think Minnesota, Wisconsin, upstate New York).
- Intermediate-Day (Medium-Day) Onions – Need 12–13 hours of daylight. Perfect for the Midwest and mid-Atlantic states.
- Short-Day Onions – Need 10–12 hours of daylight. Best for the southern U.S., including Texas and Florida.
Updated Tip (2025): Many seed companies now label onion types with a “zone suitability map” on the packet or in online listings—use this to ensure proper variety choice.
2. Planting: Sets, Transplants, or Seeds?
You have three options for starting onions:
Sets / Sprigs (Transplants)
Sold at garden centers in bundles, these are already-started baby onions ready to plant. They’re easy and save time, but often come in limited varieties. Organic transplants are more available in 2025 but still cost more.
When to Plant (Dallas example): January–early February.
Plant ¾ inch deep and 3 inches apart in rows spaced 12–18 inches. Water in well.
Seeds
Growing from seed gives you complete control over variety and growing method—important if you want organic onions.
Southern Timing: Plant outdoors in October in the South. Seeds sprout in warm fall soil, grow roots, and overwinter. Protect with straw mulch and uncover in late January.
Northern/Midwest Timing: Start seeds indoors 10–12 weeks before last frost and transplant out when soil is workable in the garden.
Plant seeds ¼ inch deep, 1 inch apart. Thin to 3 inches apart when seedlings are about 6 inches tall. Use thinnings as tasty green onions.
Updated Tip: Pre-coated pelletized seeds are now common and make planting tiny onion seeds far easier to handle.
3. Fertilizing for Strong Bulbs
Onions are heavy feeders.
- Before planting: Work 2–3 lbs of balanced fertilizer (10-10-10 or similar) into each 100 sq ft of bed.
- Midseason: When plants have 5–6 leaves, side-dress with ½ cup fertilizer per 10 ft of row. Apply between rows, not directly on plants, and water in well.
Updated for 2025: Many gardeners are shifting to slow-release organic options like alfalfa meal or fish bone meal to boost soil health and reduce runoff.
4. Watering
Onions form the largest bulbs with consistent, deep moisture.
- Water 1 inch per week in mild weather, 2 inches during heat.
- Drip irrigation is ideal—keeps foliage dry and reduces disease pressure.
- Stop watering about 1 week before harvest for better curing.
5. Pests & Problems
Onions have few major enemies, but keep an eye out for:
- Thrips – Tiny insects that damage leaves. Control with insecticidal soap or neem oil if infestations are heavy. Be careful not to use these when the temperature is over 80 degrees F or they will burn your onions.
- Fungal spots – Brown tips or spots may indicate fungal issues; treat with approved fungicides or sulfur-based products if needed.
Updated Tip: In 2025, integrated pest management (IPM) is the go-to—monitor your crop, attract beneficial insects, and treat only if pest levels exceed damage thresholds.
6. Harvest & Storage
Onions are ready when most of the tops have fallen over naturally. Gently loosen the soil, lift bulbs, and let them cure in a warm, dry, shaded, well-ventilated area for 1–2 weeks.
Once cured, store in mesh bags or crates in a cool, dry spot. Sweet varieties store for 1–2 months; pungent storage onions can last 6 months or more.
Free Downloadable Checklist to growing great onions.
Final Thoughts
Whether you’re planting a small backyard bed or filling rows in a larger garden, onions reward good planning and attentive care with months of flavor in the kitchen. Choose the right day-length variety, feed and water consistently, and harvest at the right moment, and you’ll have crisp, flavorful bulbs you can proudly say came from your own soil.
If you found this blog post useful, check out my full onion-growing guide and discover more expert gardening pamphlets and digital downloads—all designed to help you grow the best veggies right in your own backyard. All About Growing Onions is available on Amazon.
If you have gardening questions, book a call or email me at stephanie@allaboutgardeningguides. I charge $25 for up to 15 minutes.
