Growing Short-Day Onions in Zone 9a: A Complete Guide for Raised Bed Gardeners
Onions are one of the most rewarding cool-season crops to grow in Zone 9a — and if you choose the right type, you can enjoy large, sweet bulbs that store beautifully. In our warm Gulf Coast climate, short-day onions perform best, and raised beds make growing them even easier. Here’s everything you need to know to plant, care for, harvest, and store onions successfully.
Why Short-Day Onions Are Best for Zone 9a
Onions form bulbs based on day length, not plant age.
Short-day varieties begin bulbing when days reach 10–12 hours, which happens early in spring here in Southeast Texas. That means:
They bulb earlier, before heat stress becomes an issue.
You get larger, better-quality onions than you would with intermediate- or long-day types.
They can be planted in late fall to early winter when temperatures are mild.
Popular short-day varieties for Zone 9a:
Yellow: Texas Legend, Texas 1015Y,
White: White Bermuda, Texas Early White
Red: Red Southern Belle, Red Creole
Proper Timing for Planting
Timing is everything with onions.
Best Planting Window
Late November through January
This allows plants to establish strong roots before the day length changes and bulbing begins.
Why This Matters
Planting too late = small bulbs
Planting too early = potential cold damage or premature bolting
In Zone 9a, this timing gives onions 90–120+ days of growth before bulbing.
Preparing Raised Beds for Onions
Raised beds offer several advantages:
Fast drainage (onions hate soggy soil)
Loose soil for proper bulb expansion
Warmer soil temperatures in winter
Ideal Soil Mix
Onions grow best in:
Loamy, loose soil
pH around 6.0–6.8
High organic matter (add compost before planting)
Planting Onions in Raised Beds
Most Zone 9a gardeners use onion slips (transplants). Sets and seeds are less reliable here.
Spacing
4–6 inches between plants
12–18 inches between rows
Plant slips ¾–1 inch deep — too deep can restrict bulb size.
Sunlight
Full sun is essential.
Aim for 10-12 hours of direct light.
Caring for Your Onions
Onions are light feeders early on, then heavy feeders as bulbing begins.
Watering
Keep soil evenly moist, not drenched.
Water deeply 1–2 times per week depending on rainfall.
Reduce watering once tops begin to fall over before harvest.
Fertilizing
Onions love nitrogen until bulbing starts.
Apply:
A nitrogen-rich organic fertilizer every 2–3 weeks during early growth (fish emulsion, blood meal, feather meal).
Stop high-nitrogen feeding once you see bulbs begin to swell — at this point, they shift energy from leaf growth to bulb formation.
Weeding
Onions cannot compete with weeds.
Hand-pull carefully — their shallow roots are easily disturbed.
When & How to Harvest
You’ll know onions are ready when:
50–75% of the tops naturally fall over
Bulbs are large and the papery skins have formed
To harvest:
Gently lift bulbs with a fork or by hand.
Lay them out in a warm, dry, shaded area for 7–10 days to cure.
Do not wash bulbs — keep them dry.
Curing & Storage
Proper curing is essential for long storage.
How to Cure
Spread onions out in a single layer
Provide airflow and shade
Tops and roots will dry and become papery
Storage Tips
After curing:
Trim tops to 1 inch
Store in mesh bags or crates
Keep in a dark, dry place around 45–60°F
Sweet onions have a shorter shelf life because they contain more moisture. Expect 1–2 months.
More pungent varieties may store 3–6 months.
Final Thoughts
Growing short-day onions in Zone 9a is simple once you understand timing and day-length sensitivity. With raised beds, loose soil, and consistent care, you can harvest beautiful bulbs that your kitchen will appreciate for months.
