By Jim McCausland, Sunset Magazine

Dear Fresh Dirt,

I was curious...are coffee grounds good for azaleas?  I remember hearing my Mom mention this.  Do azaleas require any special care?

Thank you for your help.

Patricia

Thanks for the question, Patricia. 

Three years ago we had Soil and Plant Lab run an analysis on Starbucks coffee grounds, since those are given away freely at each of their stores. We were curious about its value as a soil amendment or mulch.

With a soil pH of 6.2, coffee grounds are slightly acid—just what azaleas like.

Salt content is a bit high, but not enough to be worrisome.

Levels of nitrogen (a primary nutrient), calcium (a secondary nutrient), and zinc, manganese and iron (micronutrients) were too low to benefit plants. But levels of phosphorus, potassium (both primary nutrients), magnesium (a secondary nutrient), and copper (a micronutrient) were high enough that, in th words of the report, "coffee grounds will negate the need for additional sources of [these] when blended with mineral soils." That's good news—free fertilizer.

To answer the second part of your question, azaleas don't need special care, but they need consistent care to do well. Mulch them (coffee grounds are fine) to keep roots cool and moist, water regularly, give them filtered sun or partial shade depending on the type of azalea you have and where you live (more shade in hotter, drier climates).

For more information about azaleas, go to Sunset's online Plant Finder.

--Jim McCausland