S
Stephen Albert
Guest
Onions aren’t just one-size-fits-all when it comes to growing conditions—daylength plays a huge role in determining how and when bulbs form. Choosing the right variety for your latitude is essential for getting big, healthy onions that store well.
After years of trial and error (and a few tiny, disappointing bulbs), I’ve learned that knowing your onion’s daylength requirement is the key to success.
Onion bulbs
Onions start bulbing when daylight hours reach a certain threshold:
The closer you are to the equator, the shorter your summer days—meaning you’ll need a short-day onion. Farther north, you’ll need intermediate or long-day types.
If you plant a long-day onion in the deep South, it will never get the daylength it needs before heat stress sets in—resulting in small bulbs. Likewise, planting short-day onions in the far north means they’ll bulb too early, before leaves have time to develop.
When I first moved from Zone 8 to Zone 5, I planted my favorite short-day onions out of habit. The result? Golf ball–sized bulbs and a big lesson learned about daylength.
The post Daylength and Onion Growth: Understanding Short, Intermediate, and Long-Day Varieties appeared first on Harvest to Table.
Continue reading...
After years of trial and error (and a few tiny, disappointing bulbs), I’ve learned that knowing your onion’s daylength requirement is the key to success.
Onion bulbs
How Daylength Influences Bulb Formation
Onions start bulbing when daylight hours reach a certain threshold:
- Short-Day Onions: Begin bulbing with 10–12 hours of daylight.
- Intermediate-Day Onions: Start bulbing at 12–14 hours.
- Long-Day Onions: Require 14–16 hours before bulb formation begins.
The closer you are to the equator, the shorter your summer days—meaning you’ll need a short-day onion. Farther north, you’ll need intermediate or long-day types.
Matching Onion Types to Your Region
| Onion Type | Best For | Daylength Needed | Typical Harvest Time | Examples |
|---|---|---|---|---|
| Short-Day | Southern U.S., subtropics | 10–12 hrs | Late spring–early summer | ‘Texas 1015’, ‘Yellow Granex’ |
| Intermediate-Day | Mid-latitudes | 12–14 hrs | Early–mid summer | ‘Candy’, ‘Red Candy Apple’ |
| Long-Day | Northern U.S., Canada | 14–16 hrs | Mid–late summer | ‘Walla Walla’, ‘Copra’ |
Why Choosing the Wrong Type Hurts Yield
If you plant a long-day onion in the deep South, it will never get the daylength it needs before heat stress sets in—resulting in small bulbs. Likewise, planting short-day onions in the far north means they’ll bulb too early, before leaves have time to develop.
My Experience Tip
When I first moved from Zone 8 to Zone 5, I planted my favorite short-day onions out of habit. The result? Golf ball–sized bulbs and a big lesson learned about daylength.
The post Daylength and Onion Growth: Understanding Short, Intermediate, and Long-Day Varieties appeared first on Harvest to Table.
Continue reading...