Why Are My Dwarf Rhododendrons Having Some Leaves Turn Reddish This Fall And Drop Off?

Question

I have 6 Capistrano dwarf rhododendrons planted 2 springs ago. They face west but there’s a very large maple shading them most of afternoon. This did not happen (reddish leaves) until this fall. They grew very well before.

• 

Answer 1

Typically, this is a general response to stress. Either the pH of the soil is off, a possible sulfur or phosphorus deficiency, wet soils, or too much light. You can test for pH issues, moisture problems, and soil deficiencies.

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm

Here are some articles to help you with the care of Rhododendrons:

https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron

Answer 2

Drought can cause some leaves, entire branches or entire plants to die. Make sure that the soil is getting sufficient and consistent moisture (the soil should feel moist, not dry or wet, at all times). The roots are very shallow, about 4 inches r so so insert a finger into the soil to monitor the moisture daily (does it feel dry, moist or wet). Too much wetness at a depth of 4" or so can cause root rot. Research too if borers may have also damaged the affected branch(es) to rule out that pest.Hope you have more yellow blooms!