Growing Potatoes Organically: From Planting to Harvest

Supermarket potatoes are often treated with sprout inhibitors, which prevent or significantly delay sprouting even under favourable conditions, making planting results unreliable. Certified seed potatoes, by contrast, guarantee freedom from viruses — potatoes can be infected by more than 25 viruses that accumulate generation after generation, steadily reducing yield, often with symptoms only becoming visible years later.

Once the foliage is removed, the tuber skins thicken and toughen, since the plant no longer invests energy above ground and instead channels nutrients into the tubers during a short, concentrated ripening phase. Without this thickened skin, freshly dug potatoes bruise easily during harvest and store for a significantly shorter time, since damaged surfaces allow rot to set in much faster.

Light exposure triggers chlorophyll production in the potato tuber, causing green discolouration on the skin — at the same time, though not causally linked, the concentration of a natural toxin called solanine also increases, which in larger amounts can cause nausea, stomach cramps and neurological symptoms. Green patches are a good visual indicator that a tuber has been exposed to light, so as a rule of thumb these areas should be generously cut away, and in cases of severe greening it’s best to discard the tuber entirely.

The Bt var. tenebrionis strain produces specific crystal proteins that activate and paralyse only the digestive systems of leaf beetles (family Chrysomelidae, which includes the Colorado potato beetle), while remaining harmless to other insect groups such as beneficial pollinators or predatory insects. Since the active compound only takes effect after ingestion, inside the larva’s gut, spraying must be timed to the young larval stage, when they are actively feeding on the leaves.