🧅
Onion
Yellow (Stuttgarter)
AlliumsDirect SowTransplant
☀️
Sun
full sun
💧
Water
Every 5 days
🌱
Germination
10 days
🕐
Days to harvest
110 days
📏
Planting depth
0.5 inches deep
↔️
Row spacing
12 inches
When to Plant
Start indoors 10 wks before last frost
Growing Guide
Soil: well-drained loamy · pH 6.0–7.0
Loose, fertile, well-drained soil is essential. Work in aged compost 4–6 inches deep. Avoid fresh manure which promotes leaf growth at the expense of bulb formation. Raised beds with excellent drainage are ideal.
- Start seeds indoors 10 weeks before last frost, sowing ¼ inch deep
- Grow under bright grow lights 14–16 hrs/day — onions need long days to bulb
- Transplant when stems are pencil-thick and nights are reliably above freezing
- Plant 1 inch deep, 4 inches apart in rows 12 inches wide
- Side-dress with nitrogen fertilizer when bulbs begin to swell (6–8 weeks after transplanting)
Care
💧 Water every 5 days
🌿 Fertilize every 21 days
📐 Spacing: 4 inches apart · 12 inches between rows
Recommended sub-rows: 3
Harvest & Storage
Ready in 110 days with a harvest window of 14 days.
- Harvest when tops fall over naturally — don't force them
- Bend any remaining upright tops by hand to speed curing
- Lift carefully with a fork; bruising causes rot in storage
- Allow bulbs to dry in the field for 1–2 days in dry weather before bringing in
Storage
Cure in a warm, dry, ventilated location for 3–4 weeks until neck is bone dry. Store in mesh bags or wooden crates at 32–40°F. Properly cured yellow onions keep 6–8 months.
Companion Planting
Grows well with:
carrotbeetlettuce
Keep away from:
beanpea
Essential Tools
- Transplant dibber or trowel
- Garden fork (harvest)
- Mesh bags (curing and storage)
- Grow lights (starting from seed)
Pests & Diseases
- Onion thrips: silvery streaking on leaves — reflective mulch deters; avoid drought stress
- Fusarium basal rot: mushy base — 3-year crop rotation essential
- Downy mildew: blue-grey fuzz in wet weather — improve plant spacing and drainage