Evergreens in a Hurt Locker
Is it just me, or do evergreens out there look like heck? Thin, sparse canopies. Dead branches. Brown, yellow and orange should be colors of vegetables, not conifers.
Two decades of drought and excessive heat has left many plants, especially evergreens, stressed and weakened. Evergreens are exquisitely sensitive to moisture loss. Exposed needles of evergreens such as spruce, pine, and arborvitae are at the mercy of nature as cold winds pull moisture from the leaves, killing them. And when trees are stressed they cannot defend themselves against insects and disease.
Two common fungal diseases attack drought stressed evergreens: CYTOSPORA CANKER and RHIZOSPHAERA NEEDLE CAST
CYTOSPORA CANKER: Fungus typically shows scattered branch dieback, often starting on the lower branches. A close look at the dead branches usually reveals the presence of sticky white sap. Infected trees produce this resinous sap in response to the infection by the canker fungus.
RHIZOSPHAERA NEEDLE CAST:
The disease is usually first evident on lower branches and then works upward gradually. Interior needles turn a purple or brown color and eventually fall from the tree. After several successive years of needle loss branches may die. In general, trees appear to die from the bottom upward.
As with many diseases, the best control is prevention.
- Avoid planting Colorado blue spruce, the most disease-prone evergreen.
- Plant trees in a good site, one that is well-drained, allows unrestricted growth and good air flow as the tree matures.
- Adding mulch around trees increases overall health in many ways, including reducing competition from turf grass.
- Keep trees well watered.
- Avoid fertilizing a drought stressed tree. Fertilizers contain salts that can pull more moisture from already dry roots.
- Remove the landscape rock, fabric and edging. This prevents water and nutrients from getting to the root system of the tree.
- Avoid planting in rows close to the highway as a buffer. These trees are vulnerable as de-icing salt spray from highway trucks wicks moisture out of roots and leaves.
Drought Tolerant Evergreens to Try:
- Juniper (all shapes and sizes)
- Eastern Red Cedar
- Serbian Spruce
For more information on avoiding disease: The Crossroads of Climate Change
Thanks for reading. Happy Planting!
President & Founder