When Portuguese laurel’s (Prunus lusitanica) evergreen leaves turn yellow, something may be seriously amiss. Hardy at U.S. Department of Agriculture plant hardiness zones 7 through 9, this resilient tree should offer year-round luster and beauty. Several underlying issues could be behind yellow Portuguese laurel leaves. Identifying the issues and creating prompt corrections may restore your tree’s health and attractiveness.
Many conditions cause yellowing leaves, also called chlorosis, but all boil down to a lack of chlorophyll. Healthy green leaf colour depends on chlorophyll, which relies on plant nutrients. If something interferes with nourishment — either a true nutrient deficit or conditions that prevent their flow — chlorophyll decreases and leaves turn yellow. This occurs on a small scale when Portuguese laurels naturally discard their leaves that are oldest. Leaf connections weaken, leaves yellow and then fall. Minor yellowing of your Portuguese laurel’s oldest, lowest leaves is not cause for concern, but prevalent yellowing indicates something abnormal at work.
Yellow leaves offer invaluable clues. In plants sensitive to low or high soil pH, foliage shows symptoms of mineral deficiency — even if nutrients are found. Portuguese laurel does nicely in highly acidic to highly alkaline soil, so pH is not a likely culprit. Moreover, most soils contain adequate nutrients. When deficits do exist, nitrogen and iron are the most common deficiencies. Deficiency of nitrogen turns whole leaves yellow, beginning with older leaves. Iron deficiencies yellow the tissue involving little veins on young leaves. If your leaves imply you and deficiencies rule out other causes, a fertilizer designed for acid-loving plants securely provides nitrogen and iron. Mix 1 tablespoon of water-soluble, 30-10-10 fertilizer with 1 gallon of water and water the plant’s soil.
The very same symptoms that result from lost nutrients occur when something hinders the utilization of available nutrients. Poor root health or injury brought on by improper watering is a common cause of yellow leaves. With overwatering or underwatering, stressed plant origins close down and stop absorbing nutrients needed for healthy green foliage. A Mediterranean native, Portuguese laurel manages moist to dry soil, clay to sand and drought. But it does not tolerate soggy dirt. Overwatering suffocates the plant’s origins, resulting in chlorotic leaves and eventual root decay. Leaves yellow and fall rapidly, and conditions worsen when cold dirt inhibits root activity even more.
Yellow leaves need hands-on intervention. Use a hand trowel to carefully dig down, trowel-length deep, close your Portuguese laurel’s roots. The dirt ought to be trendy and slightly moist — neither moist, nor completely dry. If it’s dry, then your tree requires watering; if moist, it’s overwatered. Foul-smelling dirt signals origins may have begun to rot. Gently expose the top of the root ball to assist overly wet plants dry out. Allow the area dry thoroughly. Limit neighboring lawn irrigation that may reach the plant’s origins. When you water, cover the elongated root area out to the tree drip line. Water only as needed to supplement rain, and continue to track dirt by hand. Established Portuguese laurel demands little supplemental water under normal conditions.