Why do onion tops fall over before harvest?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.Onion top flopping is not always a disaster; it can be a sign that nature is letting you know it is time to harvest. When it happened to half of my crop at 80 days, I panicked! Turns out, it was the indicator that they were ready to harvest. The crux of the issue is that neck softening starts internally about 1-2 weeks before tops flop. The 'Copra' onion variety will usually flop their tops all at once, while many heirloom varieties will flop at different times.
Natural Maturity Signs
- 50-70% of tops fall naturally at harvest readiness
- Neck skin thins and wrinkles visibly
- Occurs 100-120 days after planting for most varieties
Problem Indicators
- Mushy neck base = overwatering/rot
- Chewed stems = onion maggot larvae (check for white grubs)
- Yellow streaks = nitrogen deficiency (apply fish emulsion)
Harvest Timing
- Lift bulbs when 60% tops have fallen
- Delay harvest after rain (bulbs absorb water)
- Cut roots 1 inch (2.5 cm) below bulb immediately
Diagnose properly by digging even one bulb, when you gently squeeze the neck of the bulb and it gives slightly that means you need to harvest now. If the bulb is mushy you need to act fast. My worst case of rot spread to 20 plants in just one night. I never water until after checking the soil moisture with a probe, unless the tops are beginning to fall over.
Cure properly for long-term storage. I lay bulbs facing tops on screens in a shed at 75F (24C) for 3 weeks. Never be in a hurry to do this - I lost about 50 percent of them when I hurried the cure in 2020. Properly cured, Patterson bulbs will last over 8 months when their skins are crispy and dry.
Read the full article: When to Plant Onions: Expert Guide for Perfect Bulbs
