Exposure to frost, wind, drought or excessive nitrogen fertilizer causes azalea burn. Less is more when it comes to fertilizing azaleas because they are not heavy feeders. "Azaleas have low nutritional requirements compared to other shrubs," according to the Clemson University Extension. Burn symptoms include brown leaf edges and tips and leaf drop. Good cultural care for azaleas includes planting in a sheltered site with partial shade, in organically maintained soil with a slightly acidic pH of 4.5 to 6.0. There are several steps to take to recover a fertilizer-burned azalea plant.
Things You'll Need
Mulch (shredded bark or dry leaves)
Commercial or homemade organic, mature compost
Flush the plant with water several times. Fill a potted plant to the brim with water until it runs freely from the drainage hole. Repeat twice. This flushes out any remaining fertilizer deposits. Check for adequate azalea drainage in outdoor landscape areas. Burn problems are intensified by inadequate drainage.
Prune tips of the plant that are brittle or dead. A renewal pruning gives the azalea energy for new growth. Normal pruning takes place in early spring and new buds form by midsummer. It may take several months for a burned azalea to show signs of recovery.
Spread a 2- to 4-inch layer of mulch, such as shredded bark around the azalea plant 2 inches in diameter from the main stem. Burned roots are protected by the mulch layer. Mulch such as dry leaves release nutrients slowly into the soil.
Continue with the recommended cultural practices as the azalea plant recovers. Do not fertilize until the following year. Use organic, mature compost or organic azalea-blended fertilizer with balanced nitrogen content.
Azaleas benefit from 4-5-4 balanced organic fertilizer. Use organic azalea fertilizer derived from natural sources of nitrogen, such as cottonseed meal, fish bone meal, alfalfa meal, feather meal and mined potassium sulphate. Organic compost used as a soil additive contains 4 billion beneficial microorganisms per teaspoonful. Microorganisms such as fungi, protozoa, micro-arthropods and earthworms assist in water transport, oxygenation and nutrient recycling. Azaleas benefit from the healthy soil biology created by organic compost.
Flushing potted azaleas does not heal the burn symptoms that have already developed but prevents further fertilizer damage. Azaleas do not have to be fertilized routinely during the growing season. Fertilizer application should be based on the appearance of the plant, soil tests and correction of a mineral deficiency if needed.