Planting for the 2024 Onion Seed Crop

Alan and Robert at Garlico are contracted to grow onion seed annually. Here they are with their crew hand-planting onion sets (immature bulbs) which will spend the next eight months growing and preparing for harvest, as seed in February 2024.

Before planting, the sets needs cold storage for at least four weeks to trigger the growth of scapes or stalks. it’s a process called vernalization. The optimum time to plant sets (bulbs) is when the ground has warmed to about 13°C. After leaf growth is complete, each plant will send up one or more stalks for flowering.

These onions are honeybee-pollinated, so at planting they need to be isolated from other onion varieties by at least 1.5km to maintain the integrity of the variety. That includes distances from other commercial growers or even home gardens. Or, if growing multiple seed for different varieties, different colours or different shapes then more distance is needed to stop the bees from cross-pollinating the varieties. Like all allium species, onions produce balls that look like pompoms and are covered with tiny flowers ready for pollination.

Clear, warm weather is best for pollination, and temperatures between 18.5°C and 35°C are best for seed set. Rain can cause disease during flowering and seed set so it’s important to plan planting to coincide with optimum conditions.

Seeds ripen about six weeks after pollination and need to be de-sexed before harvesting to remove the infertile male seed heads.  Harvesting begins when the little capsules within the seed heads are open and the black seeds are visible.  The fun doesn’t stop on harvest.  The hand harvested seeds need to be dried, threshed and cleaned before being transported to the seed merchant.