Planting Guides

When to Plant Onions in Pittsburgh: Complete Guide + Best Varieties for Zone 6b

Pittsburgh, Pennsylvania

USDA Zone 6b

Last Frost: Apr 25

Last updated: October 30, 2025

Learn when to plant onions in Pittsburgh with specific dates for Zone 6b. Compare 6 varieties, get a complete timeline, and discover which onions grow best in Pennsylvania.

LLinda Kowalski

October 30, 2025

Fresh onion bulbs harvested in Pittsburgh Zone 6b garden showing successful long-day onion cultivation — — Image © PlantReference.org 2026

TL;DR

Plant onions in Pittsburgh between March 15-April 15 for Zone 6b. Choose long-day varieties like Allium cepa 'Red Wing' or Allium cepa 'Walla Walla' that require 14+ hours of daylight to bulb properly. Plant garlic cloves October 15-25, 4-6 weeks before ground freezes. Pittsburgh's 178-day growing season is ideal for storage onions that cure well for winter use.

Frequently Asked Questions

When exactly should I plant onion sets in Pittsburgh?

Plant onion sets in Pittsburgh between March 15 and April 15, depending on soil conditions. The soil should be workable (crumbles in your hand rather than forming a muddy ball) and consistently above 35°F (2°C). Small sets smaller than a dime work best—larger sets tend to bolt prematurely in our variable spring weather. Plant sets pointed end up, 1 inch deep, spacing them 4 inches apart in rows.

What onion varieties grow best in Pittsburgh's Zone 6b climate?

Pittsburgh gardeners need long-day onion varieties that require 14-16 hours of daylight to form bulbs. Allium cepa 'Red Wing' is excellent for long-term storage lasting 8-10 months. Allium cepa 'Walla Walla' produces sweet, mild bulbs perfect for fresh eating but only stores 1-2 months. Allium cepa 'Yellow Sweet Spanish' creates the largest bulbs, often exceeding one pound, with moderate 4-5 month storage life.

Can I plant onions in fall in Pittsburgh like I do in the South?

Fall planting onions for bulb production doesn't work reliably in Pittsburgh's Zone 6b climate. Our winters are too harsh for most overwintering onion varieties, and long-day types won't bulb properly with fall planting timing. Stick with spring planting March through April for best results. However, you can plant garlic cloves in fall (October 15-25) and Allium fistulosum for continuous green onion harvests.

How do I know when my Pittsburgh onions are ready to harvest?

Harvest onions when 50-75% of the green tops have fallen over naturally, typically in mid to late August for spring-planted crops. Don't push tops over manually—this damages the neck and prevents proper curing. The bulbs should feel firm, and outer skins should be beginning to turn papery. Pull onions on a dry day and begin curing immediately in a warm, dry, well-ventilated area.

Why did my onions bolt instead of forming bulbs?

Bolting (sending up flower stalks) typically results from planting sets that are too large, temperature stress, or using the wrong day-length variety. Choose onion sets smaller than a dime, as larger sets are physiologically older and bolt-prone. Ensure you're using long-day varieties appropriate for Pittsburgh's latitude. Late spring cold snaps after warm weather can also trigger bolting in stressed plants.

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Written By

Linda Kowalski

Linda's been growing tomatoes in containers on her suburban Pittsburgh balcony—ever since her kids grew up and she finally had time for hobbies again. She's a medical billing specialist by day and a tomato enthusiast by night and weekend. Linda started documenting her container growing experiments on a simple blog and discovered other renters and condo dwellers were desperate for practical advice. She tests different varieties every season, tracking yields, disease resistance, and flavor in a detailed spreadsheet. Linda's approach is practical and budget-conscious—she saves seeds, reuses containers, and makes her own fertilizer from kitchen scraps. Her specialty is maximizing production in small spaces, and she's perfected the art of growing full-size tomatoes in 5-gallon buckets. She's a Pennsylvania Master Gardener and teaches container growing workshops at her local library.