Cold Storage for Onion and Garlic: Curing and Humidity Control

Onion and garlic storage gets lumped in with general vegetable cold storage more often than it should, and that mistake costs Bangladeshi traders real money every year. Potatoes, leafy vegetables and most produce want cold and humid conditions to slow respiration and prevent wilting. Onion and garlic want the opposite on the humidity side — they need to be kept dry, well-ventilated and, for a portion of the storage period, deliberately warm before they ever go into cold storage at all. Store them like potatoes and you get soft rot, sprouting and the distinctive smell of a warehouse full of spoiling alliums within weeks.

Curing comes before cooling, not instead of it

Before onion or garlic ever reaches a cold room, it needs to be cured — dried under warm, well-ventilated conditions until the outer skin layers and the neck tissue (where the leaves met the bulb) dry out and seal. This curing process, typically done in the field or in a ventilated shed for one to three weeks depending on humidity and airflow, is what gives the bulb its protective outer layer against moisture loss and pathogen entry during the months of storage that follow. Bulbs that go into cold storage without proper curing rot from the inside, because the neck tissue never sealed and moisture keeps entering through it. This is the single most common reason a batch of stored onions goes bad even when the cold room itself is working perfectly — the fruit was never actually ready for long-term storage.

Stacked sacks of onions in a dark ventilated storage warehouse

Why low humidity is the whole point

Once cured onion or garlic goes into storage, the target environment is cold and dry — low relative humidity, in contrast to almost every other stored crop. High humidity around stored bulbs encourages root and mold growth and accelerates rot, even at low temperatures. This is the opposite of how a potato or leafy vegetable cold room is run, and it is exactly why a general-purpose vegetable cold room, tuned for high humidity to prevent wilting, is a poor fit for onion and garlic storage without modification. A cold room built specifically for allium storage needs dehumidification capacity built in, not just refrigeration, along with enough airflow between sacks or crates to prevent moisture building up in pockets where air cannot circulate.

Ventilation and stacking matter as much as the thermostat

Bulbs stored in tightly packed sacks or deep bins trap the moisture and heat that individual bulbs naturally give off through respiration, even in cold storage, and this trapped moisture is often what starts a rot outbreak that spreads through an entire stack. Mesh sacks, ventilated crates and stacking patterns that leave air channels between rows are standard practice in commercial onion storage precisely because airflow matters as much as the refrigeration setting. A cold room with excellent refrigeration but poor internal air circulation will still develop hot, humid pockets where spoilage starts and spreads before it is even noticed, since the thermostat reading the room’s general temperature will not reflect what is happening inside a densely packed sack.

Bangladesh’s specific storage challenge

Bangladesh imports a significant share of its onion supply, particularly from India, and domestic production is concentrated around a harvest window that does not match year-round demand. This creates a real incentive for traders to hold onion in cold storage through the gap between domestic harvest and the next import cycle, timed against price movements. But this only works if the stored product actually survives the holding period in sellable condition — a warehouse full of onions that rot in storage is a direct loss on top of whatever was paid for the stock, and Bangladesh has seen exactly this play out at scale during periods of onion price volatility, when traders held large volumes in storage that was not built for the crop.

Garlic has its own quirks beyond onion

Garlic behaves similarly to onion in wanting cold, dry, well-ventilated storage, but it has an additional sensitivity — garlic sprouts more readily than onion when exposed to certain temperature ranges just above freezing, a phenomenon linked to the bulb’s dormancy cycle. This means the target storage temperature for garlic is more specific than a general cold room setting, and getting it slightly wrong does not just risk rot, it risks the entire batch sprouting simultaneously, which makes it unsellable as whole bulbs even if it has not visibly spoiled. This is a detail that a cold room built for general produce, without allium-specific calibration, will not account for.

What to check before committing to allium storage

Confirm the crop has been properly cured before it enters storage — storage cannot fix a bulb that was never dried and sealed
Ask whether the cold room includes dehumidification, not just refrigeration — standard humid-cold setups are wrong for this crop
Use ventilated sacks or crates and leave air channels in the stacking pattern, not dense solid blocks
Confirm the target temperature is calibrated for garlic dormancy if garlic is part of the stored volume
Plan storage duration against realistic market timing — even well-stored onion and garlic do not hold indefinitely

How long stored bulbs actually last

Even correctly cured, cold-stored onion and garlic do not hold indefinitely, and planning storage duration against unrealistic expectations is its own way to lose money on stock that technically never rotted but became unsellable through sprouting or excessive weight loss from slow moisture loss over months. The bulb continues very slow respiration even in cold, dry storage, and eventually breaks dormancy and begins to sprout regardless of how well it was stored, though good curing and correct storage conditions meaningfully extend how long that takes compared to bulbs stored carelessly. Traders planning to hold stock through a price cycle need to weigh the realistic storage window against how long they actually expect to hold the crop before selling — storage that is technically excellent but held two months longer than the crop’s realistic shelf life still ends in loss, just a slower one than poor storage would cause.

Traders who store onion or garlic across multiple seasons often find that keeping simple records — intake date, cured condition at intake, and periodic spot checks of a sample sack from each batch — makes it far easier to catch a developing rot problem early, while it is still confined to one section of the store, rather than discovering it only once the smell has spread through the whole warehouse. This is a low-cost habit compared with the value of the stock being protected, and it also gives a trader real data on how their specific storage setup performs batch to batch, which is more useful for planning next season’s storage than relying on general guidance alone.

Getting storage built for the crop you are actually holding

Onion and garlic storage is a specific enough application that it is worth describing your crop, expected volume and target holding period directly to a supplier, rather than accepting a generic vegetable cold room quotation. DE International sources cold room panels, dehumidification equipment and refrigeration components from China calibrated for allium storage, and manages the import and installation process end to end. Reach out to talk through your storage plan, or see related equipment in the shop.