The Growing Season for Onions in Zone 9A
- The best planting time for cool-season crops in general in USDA Plant Hardiness Zone 9A is between September and March. Onions do well when planted any time from October through the first half of January, with short-day varieties being the best choice, according to the Texas A&M University. Onions withstand temperatures of 20 degrees Fahrenheit, so they thrive even in the coldest of weather in zone 9A.
- Planting seeds between the beginning of October and mid-November provides the best chance for success. Transplants thrive when planted in January or February. Planting during these times helps protect against flowering, known as bolting. Flowering causes smaller, lighter-weight onions.
- Onion seeds sprout within 10 days of planting. They reach adequate size for harvesting as green onions in just eight to 10 weeks. Growing onion bulbs requires thinning to a distance of 2 to 3 inches. Bulbs take approximately three to five months to reach maturity. Onions are ready for harvest when their tops fall to the ground.
- Clip the roots and cut tops to a length of 1 inch after harvesting your onions. Save them for up to 12 months by wrapping them in foil and storing them in a refrigerator, advises Texas A&M University. Alternatively, place onions in a mesh bag and hang them in a cool, dark place. Tying the bag after putting each onion in it keeps them separate from one another. This reduces bruising and spoilage.