Experts and BHG readers answer.
Why is my althea turning yellow?
my rose of sharon showed a yellow branch yesterday and today there is yellowing on every branch. There is another one planted next to it that looks fine except flowers smaller and leaf smaller than in previous years. I assumed it to be from the crazy weather we had this spring. 2 years ago I lost another althea that was in a very dry, hot area so I assumed it was heat and drought that got that one.
I'm afraid that I can't tell from your description what is the exact cause of yellowing on your althea. As you note, severe weather conditions could be the cause of the yellowing. When the entire plant is affected, it's usually either an environmental problem or damage to main stem or root system of the plant. Examine the stems and/or roots closely for any sign of pests. If you find none, it's likely that environmental conditions are to blame.