I have been growing calla lilies in my front yard on the south side of my house under a large ash tree for about five years. Each fall I dig up the tubers and store them in the basement in a large paper bag. Each spring I turn the soil and plant the tubers about 4" deep.
The tubers are mixed, about half brilliant pink and half bright yellow.
Last year the blossoms were not so bright, so last fall I spread a nice layer of compost after I dug up the tubers, hoping that they needed some ordinary nourishment. No luck. This year the blooms failed to reach their full intensity of color, exhibiting no strong hint of the expected color, but for the most part remaining more of an olive drab color. The blossoms seem to be fully developed since some of them have grown seeds.
From what I have read on the internet, it seems that they might not be getting enough light, but I am perplexed because of the success that I had the first few years.
Is it just a matter of light to develop full colors?