The induction of flowering or improved growth in a plant following exposure to cold temperatures. Required by garlic, many spring bulbs, and some biennials to trigger their reproductive cycle.
Vernalisation is a natural requirement for biennial and some perennial plants to complete their life cycle. During winter (June-August in Australia), these plants experience prolonged cold temperatures that chemically reset their growing processes, preparing them to flower when conditions warm in spring. Common Australian garden examples include brassicas like broccoli and cabbage, as well as root vegetables such as carrots and parsnips.
In tropical and subtropical Australia (zones 10-12), vernalisation can be challenging since winters are mild. Gardeners in these regions often need to chill seeds in the refrigerator for 4-6 weeks before sowing to simulate winter conditions. This technique works well for crops like lettuce and spinach. Temperate areas (zones 8-9) naturally experience sufficient cold for vernalisation, making cool-season gardening easier.
If you're growing biennial ornamentals like foxgloves or hollyhocks, ensure they experience winter cold. Many heirloom varieties require vernalisation to flower properly. Supplies from Bunnings, including seed-raising mix and potting soil, can help establish seedlings that will vernalise outdoors through winter. Failure to provide adequate cold may result in plants remaining vegetative without flowering in their second year, disappointing many home gardeners in warmer climates.