Summer Ornamental Issues
The biggest issue that has been affecting our landscapes this year is from the winter, which most feel we never had!
Broadleaf evergreens such as boxwood, arborvitae, juniper, holly, taxus, azalea, and rhododendron have been hit the hardest by the dry, damaging winter winds that went through most of Ohio without much (if any) snow cover. Many plants were hurt again as they began to leaf out during our warmer April temperatures that suddenly dropped overnight to below freezing again.
Winter and cold injury symptoms include yellowing or bronzing tips (old and new growth) and can progress to dead branches. There may also be new growth that collapses and leaves brown/black foliage and curled tips. These dying branches made plants more vulnerable to disease and insects as spring rains went through and temperatures warmed up again. Pruning out the symptomatic areas on shrubs will help new growth fill in and cover the damage. A deep root feeding or drench with Foliar-Pak Bio 12-6-6 or Grow-In will help push new growth to cover old damage and strengthen roots to help prevent summer stress.
I have received over 30 calls, emails, and text messages about boxwoods, specifically. The cultivars “Green Gem” and “Green Velvet,” some of the smaller leaf hybrids (a mix between Korean and English), had worse injury than the Korean cultivars such as “Winter Gem” with thicker, wider leaves.
For many landscape trees, anthracnose will start to appear as leaf spots and, later in the summer, cause premature leaf drop. These diseases are typically superficial, and the sudden leaf drop can be alarming but not enough to cause long-term damage. If the crown thins to about half of what was initially on the tree, that can be cause for concern, and a deep root feeding or drench is recommended in the fall with Foliar-Pak Bio 12-6-6 or Grow-In. Preventative fungicide treatments can be done in the spring. ATS offers a multitude of appropriate fungicides to use, such as Pageant, Tourney, Eagle 20EW, or CLT 825.
Leaf chlorosis is a common issue that can pop up during early or mid-summer. Symptoms are leaf yellowing, typically starting at the margin and moving toward the main leaf vein. Many issues can cause these symptoms: pH issues leading to nutrient deficiency or toxicity; girdling roots; overwatering; or too much sun causing chlorosis that leads to leaf scorch. Foliar-Pak Chlorburst L is an excellent drench or deep root feed that will help with iron deficiencies (in pin oaks, river birch, white pine, and rhododendrons) or manganese deficiency (in red maples and sweetgums).
Summer landscape issues always bring a lot of questions about watering, prior plant health, and the age of the planting. If a property is new to you, these can be useful questions to ask homeowners or property managers. Trees and shrubs that may have leafed out and looked good in the spring can suddenly collapse in a short period of time, and narrowing down the possible cause could save others in the planting or become a lesson learned for later.
Bridget Bergey
Sales Representative
