My Mountain Laurel Leaves Are Turning Yellow & Brown and Falling Off

Answer

The blooming evergreen shrub known as mountain laurel (Kalmia latifolia) is endemic to eastern regions of North America. Mountain laurel may be affected by a wide variety of fungal diseases, which may result in the appearance of spots on the plant. In the United States, mountain laurel is a tough plant. It can grow in U.S. Department of Agriculture plant hardiness zones 4 to 9, and it is also susceptible to damage from the cold. {{!! -!! According to the Missouri Botanical Garden, mountain laurel is a kind of thick shrub that takes on a rounded shape as it matures and typically grows between 5 and 15 feet in height. Mountain laurel is the official state flower of both Pennsylvania and Connecticut. The growth rate of the shrub is around one foot each year. The ellipse-shaped leaves of the mountain laurel have a glossy dark green colour and may grow to be as long as 5 inches. Mountain laurels are intolerant of hard clay soils that do not drain well and grow best in part shade and acidic soil. Mountain laurels grow best in part shade and acidic soil. {{!! -!! The flower clusters of a mountain laurel, which normally begin to bloom in the month of May and continue to do so for many weeks, are the most alluring aspect of this plant. It’s possible that the clusters are 6 inches broad. Each solitary bloom is formed like a cup and has a width of roughly an inch. The flowers have a base colour that is white or pinkish, and they feature markings that are purple. After blooming, a mountain laurel will benefit from deadheading, also known as the removal of wasted blooms, and mild pruning in order to keep its bushy look. This is recommended by the Missouri Botanical Garden. {{!! -!! Mountain laurels are vulnerable to no fewer than 14 different kinds of leaf diseases that are caused by fungus, which flourish in circumstances that are wet and gloomy. This information was provided by the University of Illinois Extension. Cercospora leaf spot, which appears as brown patches that may be anywhere from 2 to 4 inches across, can only be avoided by a small percentage of mountain laurel specimens. However, the edges of the spots continue to be black and may take on a reddish hue, while the centres of the spots gradually lighten to a grayish-brown tone. In extreme situations, the leaf spot caused by Cercospora may inhibit plant development and even prevent flowers from opening. {{!! -!! There is a possibility that the large, round spots seen on mountain laurel are the consequence of a fungus called Diaporthe kalmiae, which causes leaf blight. The spots, which will often manifest themselves initially on the leaf’s margins, might ultimately prove fatal to the leaf. However, research conducted by the North Carolina State University Extension found that leaf blight almost rarely results in the death of an entire mountain laurel. Leaf spot, which is caused by the fungus Mycosphaerella colorata, may be identified by the presence of grey lesions that are less than half an inch in size and have red borders. {{!! -!! The disease known as chlorosis, which causes newly planted laurel leaves to become yellow, is often the consequence of an iron deficit in the soil. Chlorosis is a condition that is often seen in young leaves, and the University of Illinois Extension believes that this condition may be caused by an iron deficiency in the soil. Even if there is a sufficient amount of iron in the soil, the plant may not be able to absorb it if the soil has a pH that is higher than 6.0, which indicates that it is excessively alkaline. If the leaves on your mountain laurel shrub are turning yellow, this is an indication that the soil in your garden needs to have additional acid added to it. {{!! -!! The Michigan State University Extension suggests that the browning of leaves on evergreen species, such as mountain laurel, might possibly be the consequence of severe winter winds, which dry up the leaves at a time when the ground is often frozen and plants are unable to pull water up from the soil. Burlap may be used as a protective covering for evergreens throughout the winter to assist avoid damage.

Mountain Laurel Identification

Mountain laurel, the state flower of Pennsylvania and Connecticut, is a dense shrub that grows in a rounded form and has a typical height between 5 and 15 feet, according to the Missouri Botanical Garden. The shrub adds about a foot of growth a year. The mountain laurel’s ellipse-shaped leaves are a glossy dark green and may be up to 5 inches long. Mountain laurels grow best in part shade and acidic soil and are intolerant of heavy clay soils that do not drain well.

The most attractive feature of a mountain laurel is its flower clusters, which typically appear in May and last for several weeks. The clusters may be 6 inches wide. Each individual flower is cup-shaped and about an inch wide. The blooms have a white or pinkish base color with purple-colored markings. According to the Missouri Botanical Garden, after bloom, a mountain laurel will benefit from deadheading – removal of spent flowers – and light trimming to maintain its bushy appearance.

Spots on Mountain Laurel

According to the University of Illinois Extension, mountain laurels are susceptible to no less than 14 types of leaf diseases caused by fungi, which thrive in moist, shady conditions. Few mountain laurel specimens manage to avoid Cercospora leaf spot, which manifests as brown spots that may be 2 to 4 inches wide. The center of the spots fade to a lighter grayish-brown color, but the margins remain dark and may turn purplish. Cercospora leaf spot can interfere with plant growth and impede flowering in severe cases.

Large, circular spots on mountain laurel may also be the result of leaf blight caused by the fungus Diaporthe kalmiae. The spots usually appear first on the edge of the leaf and may eventually kill the leaf. However, per the North Carolina State University Extension, leaf blight will rarely kill an entire mountain laurel. Gray lesions less than 1/2 inch in size with red edges may be a sign of leaf spot caused by the fungus Mycosphaerella colorata.

Other Mountain Laurel Problems

Newly planted laurel leaves turning yellow, a condition known as chlorosis, is usually the result of an iron deficiency. According to the University of Illinois Extension, chlorosis is often observed in young leaves and may be due to a lack of iron in the soil. In soil that has a pH over 6.0, meaning it is too alkaline, the plant may not be able to absorb iron from the soil even if there is enough iron available. Mountain laurel bush leaves turning yellow are therefore a sign that you may need to make the soil more acidic.

According to the Michigan State University Extension, browning of leaves on evergreen species, like mountain laurel, may also be the result of harsh winter winds that dry out the leaves at a time when the ground is often frozen and plants cannot draw up water from the soil. Covering evergreens with burlap can help prevent this kind of winter injury.