Botrytis (Grey Mould) on Tulips: What It Is and How to Manage It

Botrytis is a genus of fungal pathogens responsible for two distinct but related problems on tulips. Botrytis cinerea is the common grey mould that affects many plants, attacking dying or stressed tissue. Botrytis tulipae causes the more specific and destructive tulip fire disease. Both produce similar grey mould but differ in their host specificity and the severity of the damage they cause. Understanding which one you are dealing with helps you choose the right response.

Symptoms of Grey Mould

Botrytis cinerea typically colonises dead or dying tissue first — spent flowers, damaged leaves, or the base of the stem where it meets the soil. You will see a fluffy, silvery-grey mould that produces clouds of tiny spores when disturbed. The mould then spreads from dead tissue into living plant parts, causing brown rot to develop. On flowers, petals develop water-soaked spots that collapse and become covered in grey fuzz. Stems may develop a soft rot at the base. The damage worsens rapidly in cool, damp, still conditions with poor air circulation.

Conditions That Allow Botrytis to Spread

Botrytis spores are present in virtually every garden. The fungus becomes a problem only when the microclimate around the plant remains humid for extended periods. Dense plantings, overhead watering, persistently wet weather and the presence of dead flowers or leaves all provide the conditions it needs. Once established, it spreads through direct contact and via airborne spores carried by even light movement of air.

Cultural Controls

Remove dead flowers promptly once petals begin to drop — these are the primary entry point for Botrytis cinerea. Deadhead cleanly just below the flower head, taking care not to leave a stub of stem to rot. Remove any damaged or dying leaves as soon as they appear. Improve air circulation by spacing plants adequately and avoiding dense companions that trap humid air. Water at the base of plants rather than overhead, and water in the morning so foliage dries before evening temperatures drop.

Fungicide Applications

In seasons with prolonged cool, wet spring weather, a preventive fungicide application can protect vulnerable plants. Copper-based fungicides, mancozeb or tebuconazole applied as the flowers begin to open provide the most effective protection window. Repeat applications every 10–14 days while conditions remain wet. Begin treatment at the first sign of infection rather than waiting for mould to become established — once grey fuzz appears the infection is already advanced.

After the Season

When foliage dies back, remove all plant debris thoroughly. If Botrytis has been a problem, lift and inspect bulbs before storage. Affected bulbs that show soft patches should be discarded. Store clean bulbs in dry conditions with good air circulation. Applying sulphur dust to stored bulbs reduces the risk of Botrytis developing in storage, especially in humid conditions.