Laurel, or bay laurel, with the scientific name Laurus nobilis, are plants popular for their aromatic leaves, which are used as seasoning in cooking. These plants are native to the Mediterranean region and the Eastern United States, and are also referred to as bay trees, Grecian laurel, Mediterranean bay, noble laurel, sweet bay, Roman laurel, and true laurel. These evergreen shrubs or trees can grow up to 50 feet and are commonly used as ornamentals or for privacy hedges. As with most plants, they can also be prone to certain conditions that cause yellowing leaves.
Laurel Leaves Turning Yellow: What Are The Common Reasons?
Soil conditions
Bay laurel plants thrive in well-draining acidic soil. If they are planted in alkaline or poorly-draining soil, they could develop chlorosis caused by iron deficiency, and the outcome will be yellowing leaves. Moreover, if the plants are overwatered the soil can get waterlogged, and this could lead to root rot that also causes yellow leaves.
To fix soil problems, add aluminum sulfate to the soil to enrich it with essential nutrients like iron and nitrogen. Ideally, you should test the soil’s existing pH to determine the required amount of fertilizers. Also avoid overwatering the plants to prevent soggy, waterlogged root systems.
Pest infestation
Laurel leaves could turn yellow due to pest infestations. Bay suckers are tiny, brown insects that resemble aphids. These pests suck on the plant’s sap during the late spring months and lay their eggs on the undersides of leaves. Heavy infestations that are left untreated could lead to yellowing leaves that become thick and brown, and eventually fall off.
Other pests that commonly invade laurel include aphids, scales, thrips, lace bugs and whiteflies. These insects could cause damage that leads to leaf spots, black sooty mold or other diseases.
To fix the problem, spray the affected foliage with a jet of water to dislodge the pests, and treat the infected leaves with neem oil or horticultural oil. You may also opt for low-toxicity herbicides, especially for severe infestations.
Fungal diseases
As mentioned previously, fungal diseases could develop due, in part, to the presence of pests. Warm and moist weather could also encourage fungal growth, especially in spring. Root rot and leaf spots are fungal diseases that could lead to yellowed leaves.
To treat the ailing laurel plants, prune away damaged plant parts using sterilized pruning shears. Discard all plant clippings and debris and be sure to apply fungicides to control the spread of the fungal infection.
The natural aging process of leaves
Yellowing laurel leaves could simply be part of the plant’s natural aging process. Like most plants, bay laurel leaves tend to yellow as they age, and will then be shed. Simply remove the yellow leaves and add some fertilizer, while ensuring that the area surrounding the plants is clean.
Other factors such as sunburn and over-fertilization
Too much sunlight could cause sunburn which could turn laurel leaves yellow and eventually brown. Over-fertilizing could also cause foliage to turn yellow, because it burns the roots.
To fix these issues, use a shade cloth to shield the plants from the sun’s rays. Fertilizers should be applied every spring before new plant growth, and be sure to follow label directions regarding the dosage. Remember to irrigate the soil deeply after fertilizer applications.
Laurel Plant Care and Cultivation
Laurel plants thrive in full sun and ideally should be planted in spring when they are semi-dormant. Their soil should be enriched with organic compost or well-rotted manure, along with extra grit to improve plant stability and soil drainage. Opt for a ratio of one part sand or crushed gravel to six parts enriched soil. For laurel plants in containers, make sure there are drainage holes in the pot and water moderately to prevent soggy roots.
Repot your laurel plants every two to three years and trim at least one-third of the roots while removing at least the top two inches of soil. Replant in fresh, enriched soil and replace the top layer with mature compost. Fertilize plants in containers at least every two weeks from spring until August using all-purpose fertilizers, and monthly for in-ground laurel plants.
If you live in an area with regular freeze cycles, wrap the potted laurel plants with bubble wrap until spring to protect their roots. If you have harsh winters in your area, the plants should be planted in containers and brought indoors to protect them from the harsh weather. Cover them with burlap to shield them from freezing temperatures, and protect them from strong winds by placing them in a sheltered spot.
Conclusion
Laurel plants are popular worldwide for their aromatic leaves, which are commonly used as spices for cooking. Like most plants, they are also prone to infections and conditions that cause yellowing leaves. This could be due to soil conditions, nutrient deficiency, pest infestation, fungal diseases, or the natural aging of leaves.
Image: istockphoto.com / Anna Nelidova