Introduction to Evergreen Browning: Evergreen trees turning yellow or brown can alarm gardeners, but this phenomenon is frequently a natural part of their seasonal aging. Distinguishing between normal aging and potential problems is key to proper care.
Natural Aging Process: Many healthy evergreens exhibit yellowing and browning, particularly on older branches, during autumn. This is a normal process where trees shed affected needles, causing concern among gardeners who might not recognize it as a natural cycle.
Identifying Nutrient Deficiencies: Yellowing branches could signal nutrient deficiencies. Stunted growth indicates possible nitrogen shortage, while yellowed branch tips turning reddish-brown may point to a lack of potassium. Both scenarios warrant a soil test for confirmation and can be remedied by supplementing the deficient nutrient.
Insect Damage Considerations: Insect infestations can mimic nutrient deficiency symptoms, making close inspection crucial. Dan Gilrein, an entomologist, emphasizes the importance of examining for specific pests that affect evergreens.
Common Pests and Treatments:
- Arborvitae Leafminer: This pest targets arborvitaes, appearing as tiny caterpillars that turn into tan moths. Infestations result in browned leaf tips, often mistaken for drought stress. Treatment involves early summer application of products containing Spinosad.
- Scales: These insects drain chlorophyll, causing foliage discoloration. They excrete honeydew, leading to sooty mold and ant attraction. Control involves mid-spring applications of horticultural oil.
- Spider Mites: Known for chlorophyll extraction and leaving yellow foliage, they’re active in spring and fall. A hose stream can dislodge them, and severe infestations may require horticultural oil treatment.
- Bagworms: These can cause complete browning of evergreens. Removal of their “bag” shelters or treatment with Bt insecticide in late June through July is effective.
Preventative Measures: Diversity is key in planting to avoid creating a feast for host-specific pests. Limiting any one species to 5% of your garden’s flora can prevent extensive damage from insect infestations or diseases.
Conclusion: While evergreen browning is often a natural part of the tree’s lifecycle, certain signs can indicate more serious issues. Regular monitoring and understanding specific symptoms are essential in maintaining healthy evergreens.
Further Resources: For more gardening tips and advice, gardeners can subscribe to Jessica Damiano’s Weekly Dirt Newsletter and follow her regular columns with The AP.