A very sick capistrano rhododendron plant

Asked August 16, 2020, 1:09 PM EDT

I had 2 rhodies planted on the north side of my home in 2019. Both flowered that year though one was much fuller. This spring the the one plant had what looked like small flower buds, though the other plant’s buds were much larger. I took pictures of the plants and went to the nursery where originally purchased and was told to watch the plant it will probably bloom later. It never did blossom but both plants developed buds that looked like next years flowers. Recently a branch on the weaker plant had its leaves curl and turned brown. I removed the deadening leaves and a week later other branches were doing the same thing, turning yellow to brown color. The strong plant looks great. I returned to the nursery again this week and the owner feels its a disease problem in the soil. And he said it replacing it will not redeem the problem. Need advice, would removing soil where existing plant is and replacing with new soil over approximately 3 ft dia hole.

Bay County Michigan

1 Response

Hello,

I am sorry to hear about your Rhododendron. Rhododendrons are best grown in acidic, rich, moist but well-drained soils. I’m attaching a bulletin from the Missouri Botanical Garden about Rhododendron ‘Capistrano’ which explains it’s characteristics and preferred conditions. https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=257096&isprofile=0&

Rhododendrons are susceptible to many insects and disease problems. But your problem may be cultural. The nurseryman may be correct in suggesting that the problem is in the soil. However, the two plants share the same soil so that is puzzling. Rhododendrons do not like poorly draining soil—is the struggling plant in too much water—could a downspout or a sprinkler provide more water to it than the other? Too much water may cause root rot. You can dig out the poor plant and inspect the roots. Healthy roots are white and firm, while rotting roots are black and unable to take up nourishment, air or water from the soil. If the roots are in good shape, you could pot it up in new soil to see how it handles it. If the roots are rotten, there is probably little that you can do.

Before you replace it with another Rhododendron, consider the conditions that you are planting it in. Obtain a soil test to ensure that your plants are getting the correct nourishment. https://www.canr.msu.edu/news/soil_testing_instructions_using_msu_extensions_home_lawn_and_garden_soil_te

I hope this helps you with your plant.

Thank you for contacting Ask an Expert.