Can all onion varieties be stored long-term?
Written by
Benjamin Miller
Reviewed by
Prof. Charles Hartman, Ph.D.Not all onion varieties store well, and some, like the short-day sweet Vidalia or the Walla Walla, contain more water and must be consumed within months before they spoil. Long-day types, such as Copra and Patterson, have thick skins and high solids, and can be stored for nearly a year. Choose the wrong variety, and the onions will sprout and mold, even if you cure them properly.
Long-Day Onions
- High pyruvic acid content (over 1.0%)
- 20-22% dry matter resists moisture loss
- Tight papery skins with multiple layers
Short-Day Onions
- Low solids (12-15%) increase perishability
- Thinner skins offer minimal protection
- High sugar content triggers faster sprouting
Storage Enhancers
- Dormancy period genetics delay sprouting
- Firm basal plates resist root regrowth
- Uniform bulb shape ensures consistent drying
Choose your varieties wisely for your purpose. Do you need onions to store and layer in your kitchen throughout the year? Try Copra or Patterson. Do you enjoy eating fresh summer salads? Grow Walla Walla, but be sure to preserve the leftovers. I grow 70 percent storage and 30 percent sweet onions. Otherwise, I'd be wasting food.
Extend shelf life with post-harvest techniques. Cure your short-day onions longer at temperatures of 75-80 degrees F. to toughen the skins. Store them at 32°F, and the deterioration begins to slow down. Dehydrate or pickle your excess sweet onions immediately after harvesting, before they spoil. These methods increase usable life by months.
Genetics determines how well an onion stores. No method of curing will make Vidalia onions store as long as Copra storage onions. This clearly means short-keeper types of onions will require you to use them quickly after harvest. When you know this, you will avoid frustration from wasted crops and plan your garden for continuous harvests.
Read the full article: When to Harvest Onions: Ultimate Guide
