If there’s one mistake Pennsylvania onion growers make more than any other, it’s buying the wrong variety. Short-day onions — the ones you see at most garden centers — simply won’t bulb in Pennsylvania. They’re bred for the South, where the trigger daylight length hits in early spring. In PA, by the time your days get that long, it’s already summer. You need long-day varieties.
The good news: long-day onions thrive in Pennsylvania’s zones 5a–7a, and there are excellent options for every use — sweet slicers, rock-solid keepers, and bold red varieties. This guide covers the ones that consistently perform here.
📅 Onion Growing Calendar — Pennsylvania (Zones 5a–7a)
🧅 Onion Variety Quick Reference — Pennsylvania
Why Day Length Is the Most Important Factor in PA
Onions don’t bulb based on calendar date — they bulb based on day length (photoperiod). When the number of daylight hours hits a variety’s trigger threshold, the plant stops growing leaves and starts forming a bulb instead.
Short-day varieties trigger at 10–12 hours of daylight — typical of February and March in the South. In Pennsylvania, we don’t hit 10 hours until mid-January and blow past 12 hours by late February. By the time your plant is big enough to benefit from that trigger, spring is already here and the days are getting longer, not shorter. The result: no bulb, just topgrowth.
Long-day varieties trigger at 14–16 hours of daylight, which Pennsylvania hits reliably in June and July. That’s the window where your onion tops stop leafing out and all the plant’s energy redirects into bulb formation. This is why long-day varieties are non-negotiable for PA gardeners.
Skip Intermediate-Day if North of Harrisburg: Intermediate-day varieties trigger at 12–14 hours and work fine in central and southern PA. But in northern PA (Erie, Pocono) with a shorter growing season, stick with proven long-day types for full-sized bulbs.
Best Sweet Onion Varieties for Pennsylvania
Sweet onions have lower sulfur content and higher water content than storage types — that’s what makes them mild enough to eat raw. The trade-off is shorter shelf life (2–4 weeks max). Grow these for summer eating, not winter storage.
Walla Walla is the gold standard for PA sweet onions. Large, globe-shaped bulbs with papery golden skin and mild, almost sweet flavor. Performs best in zones 6–7a. Start seeds indoors in January for best results.
Yellow Sweet Spanish is the more adaptable choice for northern PA. It bulbs reliably across all PA zones and handles shorter seasons better than Walla Walla.
Ailsa Craig Exhibition produces enormous show-quality bulbs (often 1–2 lbs) with mild, sweet flavor. Start from seed only.
Sweet Onions Need Lower Sulfur Soil: Avoid heavy nitrogen fertilizers after June and don’t plant in soil amended with fresh manure. High sulfur in the soil — not the variety — is often what makes a sweet onion taste sharp.
Free PA Planting Calendar
Zone-specific · 4 pages · Instant download
Get the exact dates for your Pennsylvania zone — when to start seeds indoors, direct sow, transplant, and harvest. Built around your local frost window, not a generic national average.
- Wall chart with all key dates
- Seed-start schedule (50+ crops)
- First & last frost reference
- Soil temp cheat sheet
Best Storage Onion Varieties for Pennsylvania
Storage onions are the practical choice for most PA gardeners. A good storage variety can keep 10–12 months in a cool, dry spot. The trade-off is that storage types are pungent raw, though they sweeten up dramatically with cooking.
Patterson is the benchmark storage onion for the mid-Atlantic. Storage life of 10–12 months is realistic with proper curing. Widely available from Johnny’s and most regional seed suppliers.
Copra has been the gold standard storage onion in the Northeast for decades. Consistently tops storage trials with 12-month shelf life in good conditions. If you only grow one storage variety, Copra is the choice.
Varsity is a newer hybrid with strong disease resistance (including Botrytis). University of Maryland Extension has noted its performance in mid-Atlantic trials as consistently competitive with Copra.
Curing Is Non-Negotiable: Even the best storage variety will rot in two months if not properly cured. Cure at 80–90°F with good airflow for 2–4 weeks before moving to cool storage.
Best Red Onion Varieties for Pennsylvania
Red onions are harder to get right in PA than yellows. But a well-grown red onion harvested in August is one of the best things in the garden, especially raw on sandwiches or pickled.
Red Candy Apple bridges the gap between sweet and storage reds. Intermediate-day type that performs well across central and southern PA. Good raw or cooked, storage is moderate (4–6 months).
Redwing is the storage-focused red option. Shelf life of 8–10 months with proper curing. Performs across all PA zones including colder northern regions.
Rossa di Milano is an Italian heirloom producing elongated, torpedo-shaped red bulbs with mild, sweet flavor. Order seed only — a genuine standout for fresh eating.
This page contains affiliate links. If you purchase through these links, we may earn a small commission at no extra cost to you.Full Onion Variety Comparison Table
Here’s a side-by-side comparison of the top onion varieties for Pennsylvania. All are long-day or intermediate-day types suitable for PA growing conditions.
| Variety | Type | Day-Length | Flavor | Storage | Best PA Zones |
|---|---|---|---|---|---|
| Walla Walla | Yellow sweet | Long-day | Very mild, sweet | 2–4 weeks | Zones 6–7a |
| Yellow Sweet Spanish | Yellow sweet | Long-day | Mild, slightly sweet | 3–5 weeks | All PA zones |
| Ailsa Craig | Yellow sweet/exhibition | Long-day | Mild, sweet | 2–3 weeks | Zones 5b–7a |
| Patterson | Yellow storage | Long-day | Pungent | 10–12 months | All PA zones |
| Copra | Yellow storage | Long-day | Pungent, intense | 12 months | All PA zones |
| Varsity | Yellow storage | Long-day | Pungent | 10–11 months | All PA zones |
| Red Candy Apple | Red sweet | Intermediate | Mild-sweet | 4–6 months | Zones 5b–7a |
| Redwing | Red storage | Long-day | Bold, pungent | 8–10 months | All PA zones |
| Rossa di Milano | Red heirloom | Long-day | Mild, sweet | 3–5 months | Zones 5b–7a |
| Candy | Yellow hybrid | Intermediate | Mildly sweet | 3–4 months | Zones 5b–7a |
Sets vs. Transplants vs. Seed — What to Buy in PA
You can start onions three ways in Pennsylvania, and the method you choose affects which varieties you can grow.
Sets are the easiest starting point but almost always generic unnamed types. You won’t find Copra or Patterson as sets — the best varieties are only available as transplants or seed.
Transplants are the best balance of convenience and variety selection. Companies like Dixondale Farms ship named varieties in March–April. Most PA home gardeners who want specific varieties use transplants.
Seed gives the widest selection and lowest cost per plant, but requires starting indoors 10–12 weeks before last frost — January through early February for most of PA.
| PA Region | Best Varieties | Start Method | Planting Window |
|---|---|---|---|
| Northern PA (Erie, Pocono — Zone 5a–5b) | Yellow Sweet Spanish, Patterson, Copra, Redwing | Transplants preferred; sets OK | Late April–early May |
| Western PA (Pittsburgh, Zone 6a) | Walla Walla, Copra, Patterson, Red Candy Apple | Transplants or sets | Mid-April |
| Central PA (State College, Zone 5b–6a) | Yellow Sweet Spanish, Patterson, Candy, Varsity | Transplants or sets | Mid-to-late April |
| Eastern PA (Philadelphia, Zone 6b–7a) | Walla Walla, Ailsa Craig, Red Candy Apple, Copra | Transplants, sets, or seed | Late March–mid-April |
Frequently Asked Questions About Onion Varieties in Pennsylvania
1. Can I grow Vidalia-type onions in Pennsylvania?
Not exactly. Genuine Vidalia onions are grown in specific Georgia counties with particular sandy, low-sulfur soils. You can grow Vidalia-type varieties (Yellow Granex) in PA, but they’re short-day onions and won’t bulb reliably north of the Mason-Dixon line. For a similar sweet experience in PA, grow Walla Walla or Yellow Sweet Spanish instead.
2. Will my garden center’s onion sets work in Pennsylvania?
Probably, but with limitations. Generic hardware store sets are almost always unnamed long-day varieties that will bulb in PA. The issue is you won’t know the variety — which means you can’t predict storage life, flavor, or disease resistance. Sets also have a higher bolting rate than transplants. For consistent results, order named transplants.
3. What’s the difference between long-day and intermediate-day onions?
Long-day onions require 14–16 hours of daylight to trigger bulbing. Intermediate-day types trigger at 12–14 hours. Pennsylvania’s summer days hit 14–15 hours, so both types will bulb in central and southern PA. In northern PA (zones 5a–5b), stick with long-day types — intermediate types may not fully develop before fall weather arrives.
4. Why did my onions bolt before forming bulbs?
Bolting is usually triggered by a sustained cold period (below 50°F for 10+ days) followed by warmth — which is exactly what happens in a PA spring. Sets are more prone to bolting than transplants. If onions bolt, snap off the flower stalk and harvest within 2–4 weeks — they won’t store.
5. Which onion varieties store the longest in Pennsylvania?
Copra and Patterson are the top storage performers, with realistic shelf life of 10–12 months at 45–55°F with good airflow. Redwing is the best storage red onion at 8–10 months. Sweet varieties should not be expected to store more than 4–6 weeks regardless of conditions.
6. Can I save seeds from onion varieties I grow in Pennsylvania?
Yes, from open-pollinated varieties — but not hybrids. Rossa di Milano, Ailsa Craig, and Yellow Sweet Spanish are open-pollinated. Copra, Patterson, Red Candy Apple, and Candy are hybrids and won’t breed true. Onion seed viability is short — use within 1–2 years.
Continue Reading: Onions in Pennsylvania
- When to Plant Onions in Pennsylvania — exact planting windows by PA zone, frost date math, and sets vs. transplant timing
- How to Grow Onions in Pennsylvania — soil prep, spacing, watering, pest control, and harvest guide
- Best Vegetables to Grow in Pennsylvania — top-performing crops across PA’s zones 5a–7a
