Harvesting onions: fresh, mature and ready for storage

Harvesting for immediate use or for storage?

For quick consumption, you can pick young onions without waiting for the leaves to dry out, as indicated by the SNHF. Harvest as needed: onions harvested for fresh use do not need the drying process required for storage bulbs.

The stage and the type are two different pieces of information. A bulb onion can be harvested young or left until maturity; the Welsh onion, Allium fistulosum, does not form the same storage bulb. Iowa State University distinguishes these uses. To store onions, also check the variety name and its advertised keeping quality: colour alone is not enough to determine this.

Recognising maturity without bending the leaves

On a crop that has reached the end of its development, the leaves naturally yellow and fall over, then dry out. The RHS advises harvesting before they disappear completely. It discourages bending the foliage or lifting the bulbs prematurely to break the roots and force maturation.

When the bulbs have reached their final size and the leaves begin to fall over, stop watering, according to the University of Minnesota. However, unusual dieback requires examining the crop: diseases and pests can also alter the appearance of the leaves.

Lifting bulbs without damaging them

If possible, choose a dry and cool day, as recommended by Minnesota. Loosen the soil with a fork, keeping a distance from the bulbs, then lift them gently. Avoid knocks and bruising: the RHS links these to the risk of rot during storage. Set aside any accidentally damaged bulbs to use quickly if they are still healthy.

Drying: observe the bulb, not just the weather

Spread the harvest with its leaves in a single layer on a clean, dry surface in a warm, well-ventilated place. Iowa State University describes this preparation before storage. If the weather turns wet, continue drying under a ventilated shelter, following the RHS.

Good weather does not prove that drying is complete. Check the outer skins and the neck, at the junction of the foliage and the bulb: the former should be dry, and the latter dry and shrunken. These are the criteria set by Minnesota. Keep bulbs still drying separate from those ready for storage.

Sorting before storage

After drying, create three groups:

• For storage: healthy, dry bulbs without damage, of a storage variety.
• Use first: healthy bulbs with a thick neck or plants that have bolted.
• To discard: bulbs showing rot; do not mix them with the stock.

The advice on sorting out bulbs with thick necks or rot comes from the Iowa drying guide; the poor keeping quality after bolting is detailed in its onion guide.

Cut the leaves after drying, leaving about 2.5 cm above the bulb, or keep them to plait the onions. The Iowa guide then recommends nets or crates that allow air circulation.

Checking stored onions

Store in a cool, dry place, free from frost, according to Minnesota. Regularly inspect the bulbs and remove any that are rotting. The variety and storage conditions determine the harvest’s longevity, notes Iowa: no single duration suits all batches.

Record the variety, lifting date, end of drying and any losses observed. To prepare for the next crop, refer to the onion guide.