The Gardener's Almanac

Grey mould

Grey mould is a form of botrytis that affects the flowers and foliage of many cultivated plants.

The spores unlike powdery mildew spores grow on dead plant material.

Normally there are two distinct symptoms, one affecting the flowers the other affecting the flower stems.

The symptoms are initiated in humid conditions by airborne spores that infect live plant tissue, particularly if it is damaged or delicate.

These cause; small spots on flowers and a grey fuzzy mould on the flower stems and petioles, often near the base, this can cause the stem/s to collapse.

As mentioned above; the fungus thrives on dead plant material, forming black, tough resting structures called sclerotia in the dead tissue.

Meaning good hygiene around the plants is often the best control i.e. keeps the area around the plant/s free from dead leaves and detritus, particularly if the plants have been affected by powdery mildew.

There are no fungicides available to the amateur gardener to control this disease, but by using the treatment suggested for powdery mildew, damage can be minimized.

Reducing the humidity around plants can also help to keep the number of spores down.