How and when to harvest bulb onions

Traders sort out onions from a car parked by the roadside in Elburgon, Nakuru County

Traders sort out onions from a car parked by the roadside in Elburgon, Nakuru County, on February 25, 2023. The cured and trimmed onions should be kept in a cool dry place.

Photo credit: John Njoroge | Nation Media Group

Desmond’s bulb onions are ready for harvest. Bulb onions are usually ready for harvest 90 to 150 days after transplanting, depending on variety and management practices. 

Harvesting onions involves removing mature bulbs from the ground and preparing them for storage or consumption.
The harvesting takes place when bulbs have reached their full size and completed the growth cycle. 

Mature onions form a shiny membranous cover around the bulbs or when foliage withers.
Harvesting should be during the dry season. This then calls for timely planting. Bulb onions easily rot during rainy seasons.

Harvesting should start when you notice 50 per cent of your crops are weak and dry. Early harvesting causes onions to spoil.
Harvesting is by uprooting the crop. In some cases, the farmer loosens the soil around the bulb to make harvesting easier. 

One should be careful to prevent causing injuries to the onions as that results in losses.
Once the soil is loose, lift the bulbs carefully.

After uprooting, the leaves are cut. In case the farmer is not selling the onions immediately, it is generally not necessary to cut the leaves, as they play an important role in curing. The leaves help transfer moisture from the bulb to the air, which aids in drying and reduces the rotting risk.

If the leaves are excessively long, they can be trimmed to make the onions easy to handle during curing. 
In this case, it is important to leave about an inch of stem attached to the bulb to prevent the onions from becoming damaged or infected.

If the onion leaves are damaged or diseased, it may be necessary to remove them. 
In this case, it is important to use clean, sharp tools to avoid further damaging the bulbs.


While harvesting, the bulb onions should be kept in clean crates or sacks to prevent them from getting infected. 
Weighing should be done to determine the amount of produce harvested.

Sorting and grading remove the affected bulb onions, while grading is done depending on the size of the onions and their quality. 
One acre should yield 18 to 20 tonnes under good management practices.

The onions are then packed in nets. In Kenya, most onions are sold in kilogrammes. The nets facilitate good aeration, which prevents the onions from rotting easily.

The cured and trimmed onions should be stored in a cool, dry and well-ventilated place. 

Onions should be kept in a single layer, with space between them to allow for the circulation of air. 
Avoid storing them near fruits or vegetables that emit ethylene gas as that causes the onions to spoil quickly.

You can store onions for three to six months if the weather is excellent and conditions are ideal. The farmer can store small onions longer than wider varieties.

After harvesting, one should incorporate crop rotation aspects to preserve the soil for the next planting season. 
This also assists in pest and disease control.

In our next article, we will look at the mitigation measures for post-harvest losses.