Dark spots and eaten leaves on perennials

(Question)

My plants leaves are turning dark brown and curl up; it was started from one of the purple cornflowers, then it spread to the other purple cornflowers, bee balm and hydrangea. Most of them are new plants in my yard but I had similar problems with my hydrangea last year. Some of the leaves are also eaten but I went out at 3am and didn’t see anything. I found earwigs in my yard last year but not sure if that’s the problem this year. Please help my plants! Many thanks!

(Answer)

I do not think that you have an insect eating your plants. Because of the extreme weather we experienced in 2012, it’s possible that your plants might be suffering from drought. The newly planted ones, especially, will not have had time to develop an extensive root system, making them more vulnerable to heat stress. It’s important to pay extra attention to watering any new plants in your garden until they become established.

While it can be hard to diagnose a problem without a picture, from your description, another possibility is that Bacterial Leaf Spot might be attacking your plants. There are several possible pathogens (Pseudomonas spp. and Xanthomonas spp.) that cause similar damage and vary in the degree of damage to the plants. Leaf Spot is favored by wet weather and it can affect a number of plants. Here are some actions you can take to slow the spread of the bacteria and further outbreaks:

  • Remove affected leaves to reduce the amount of pathogens.
  • Avoid overhead irrigation. Avoid getting the leaves wet when watering the lawn. A soaker hose system may be a good idea.
  • Allow space between plants (avoid overcrowding). Air movement allows leaves to dry faster and provide a less hospitable environment for the bacteria.
  • Never work on plants or in the garden while plants are wet since the “bruising” and other mechanical injury helps to spread diseases.
  • Eliminate plant debris as it can harbor bacteria. Do not place damaged leaves in the compost.
  • Try to plant more resistant cultivars. If you lose any of the plants this year, try planting a different plant next year.
  • Ensure good drainage.
  • Practice good sanitation of your tools. After disposing of damage leaves, clean your tools with rubbing alcohol or soak them for five minutes in a solution (9:1) of water and bleach to destroy the bacteria.

Good luck and please let us know if further symptoms develop or if you think something else is affecting your new plants.