Fertilizer Needs for Boston Ferns

Summer Feeding

• Boston ferns have their most active growth phase during the summer, and this requires more nutrients. To support this growth, apply a water-soluble fertilizer mixed at half strength once a month. Look for a fertilizer with a nitrogen-potassium-phosphorus ratio of 20-10-20. If necessary, supplement with a slow-release fertilizer, administering at half the recommended rate.

Winter Feeding

• Active growth of Boston ferns slows tremendously during the winter months. Therefore, less feeding is required, only once every two to three months and at half the manufacturer's recommended rate. Use a fertilizer with a nitrogen-potassium-phosphorus ratio between 20-10-20 and 15-0-15. It is also helpful to use distilled water in the winter to flush out any salts that have built up in the soil.

Improper Fertilizing

• The University of Minnesota Extension points out that over-fertilizing a Boston fern will cause its tips to turn brown and dry out. If the problem escalates, it will stretch beyond the tips to the entire frond. Similarly, too littler fertilizer will cause the plant to lose it vibrant green color and turn pale.

Considerations

• Along with proper fertilizing, provide the best growing conditions for a Boston fern for optimal performance. Boston ferns thrive in high humidity with low light. Boston ferns that are kept indoors during the winter months benefit from regular misting to maintain proper humidity in dry indoor conditions. The plant’s leaves will turn yellow without sufficient humidity. Monitor the plant for spider mites and mealy bugs, the most common pests of Boston ferns.