University of Maryland Extension

Excess Fertilizer/Salt Injury - Annuals, Bulbs, Groundcovers, Perennials, and Vines

brown tips on a plant

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Salt injury may occur in connection with the application of fertilizers or ice melting products. Damage due to excessive fertilizer or salt application generally appears as marginal leaf browning or leaf scorch. Salts can be toxic to root tissues causing symptoms associated with root damage, such as wilting, marginal yellowing and stunting. Leaf burn or scorch can also result from direct foliar contact with some fertilizers. Many ice-melting products contain salts, which can wash from sidewalks and roadways to adjacent planting beds. Repeated applications of ice melting products may cause salt levels to build up in the soil. In addition, many fertilizers contain soluble salts. High soluble salt levels in the soil may be the result of a single excess application or repeated applications, which cause soluble salts to build up in the soil. Factors such as soil type, irrigation practices, salt levels, and the sensitivity of specific plants can influence the amount of damage.

When diagnosing suspected salt or fertilizer injury, consider recent weather conditions. In general, damage to herbaceous plants from deicing salts or excess fertilizer is more severe in hot dry weather. Soluble salts may follow water movement through the plant and become concentrated in the leaves where moisture is lost through transpiration or evaporation. In cool, cloudy weather, when there is adequate soil moisture, the rate of moisture loss from the leaves is slower, which allows many plants to tolerate high salt levels in the spring months. That is why damage symptoms may not occur until summer, although soil salt levels have been high through the winter and spring.

Have your soil analyzed by a soil-testing laboratory if you suspect salt damage. If high salt levels are confirmed, soak the affected area with one-inch applications of water, three to four times, to help leach salt from the soil. Gypsum may be added to the soil to reduce high sodium levels caused by excessive amounts of rock salt. Soil replacement may be an option for small planting beds. Carefully measure the square footage of the planting area to avoid over application of fertilizer. To prevent problems associated with deicing salts, consult the publication, FS 707 Melting Ice Safely.

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