Why do my calla lilies not develop full color?

Question

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?

Answer 1

During five years or more, your Ash tree will have grown and now has a broader crown than it once did, even if you're unaware of it. Assuming you're still planting in the exact spot you've always done, this now means your Zantedeschia (calla lilies) are not getting enough bright light in that position, so you need to plant them further out from the canopy of the tree, or in a different position to improve their exposure to sunlight in order to get good colour on the spathes or 'flowers'.

You don't mention feeding your Zantedeschia during the growing season - its best if you can feed them monthly while they're in active growth with a balanced fertilizer, and remove spent flowers before they go to seed, unless you're saving the seed to grow later. They also do better in soil that is regularly emended with humus rich material, because despite their preference for plenty of sun, they do prefer soil that doesn't completely dry out frequently, so using good garden compost, composted manures, leaf mould, anything like that will improve moisture retention and growing conditions generally.