Brown Leaves on a Lily of the Valley

Normal Leaf Browning

• Lilly of the valley leaves die back every year toward the end of the summer. This causes leaf discoloration to yellow and brown hues. Such discoloration at the season's end is normal and does not mean the lily is diseased or unhealthy. Watering the lily of the valley can postpone this leaf discoloration if you want your lilies looking lush through the end of the summer. If the lily's leaves begin to brown during other parts of the season, the lily may need more water or it may be suffering from an infection.

Anthracnose

• Lilies of the valley affected by anthracnose have brown spots with purple borders on their leaves and stems. Infected areas die prematurely. Infected leaves should be removed as they appear. Water and fertilize the infected plant regularly to improve its ability to fight the infection. Water in the morning so the plant can dry by nightfall. Fungicide can also be applied as the plant emerges in the spring to help combat the infection.

Stem Rot

• Stem rot affects lilies of the valley living in humid conditions. During the course of the rot, leaves exhibit yellowish and grayish spots that can turn into dark brown spots that appear sunken. The fungus spreads down the stem to the lower parts of the plant. To care for an infected plant, remove the affected parts of the plant with a sharp knife and apply hot water or a bleach solution to disinfect.

Root Rot

• This soil-dwelling fungus attacks the lily of the valley as it emerges from the soil line. Leaves will appear discolored and brown as they emerge from the soil. Shoots quickly wilt. When infected with root rot, the roots will blacken and become covered with fungal threads that are white in color. There is no cure for root rot, and the entire plant dies within a few days. Infected plants should be removed along with the surrounding soil to prevent the spread of infection to other plants. The spot should not be replanted for one to two years.