Why Is My Garlic Rotting in the Ground?

Digging up garlic to find soft, rotten, foul-smelling bulbs is one of the most disheartening outcomes after months of growing. Garlic rotting in the ground comes down to excess moisture and soil-borne diseases, and because some of these diseases persist for years, it is worth identifying and managing carefully. Let me explain the causes and how to keep your bulbs sound.

Waterlogging is the common cause

Garlic hates wet feet, and the most frequent cause of bulb rot is simply waterlogged soil. Bulbs sitting in heavy, poorly drained, wet ground — especially over a wet winter or as they mature in early summer — rot rather than grow and cure. The fix is drainage: grow garlic in well-drained soil or raised beds, improve heavy clay, and ease off watering as the bulbs approach maturity (garlic wants drier conditions as it finishes). Avoiding waterlogged ground prevents a great deal of rot on its own.

White rot: the serious disease

The most feared garlic disease is white rot, a soil fungus that attacks the roots and base of the bulb, rotting it and producing fluffy white fungal growth and tiny black resting bodies (sclerotia) at the base. It is devastating because those resting bodies survive in the soil for many years — up to a decade or more — so once a bed is infected, garlic and other alliums cannot be grown there for a long time. There is no cure. The defences are strict: never plant infected stock, rotate alliums widely, and if white rot appears, remove and destroy affected plants and avoid alliums in that ground for years.

Basal rot and other diseases

Fusarium basal rot is another common cause, rotting the base plate and roots, often with the plant yellowing and the bulb going soft from the bottom — it is worse in warm, wet soils. Various other fungal and bacterial rots attack bulbs in wet conditions and through wounds. These persist on debris and in soil, so rotation and hygiene matter. They are all favoured by excess moisture, which is why drainage is the common thread in prevention.

Preventing bulb rot

To keep garlic sound: plant only healthy, disease-free cloves (certified seed garlic) in well-drained soil or raised beds, rotate alliums to fresh ground each year (essential against the soil-borne rots), ease off water as bulbs mature, and harvest at the right time before bulbs over-mature and become vulnerable. Remove and destroy any rotting plants promptly — never compost them or replant from affected stock. If white rot is confirmed, keep alliums out of that ground for many years. With good drainage, clean stock and rotation, garlic comes up firm and sound.