I thought I was growing them for a bit of easy colour but not for dyeing. And then I remembered India Flint's ice-flowers recipe from Eco Colour...
The darkest lobelias went into the freezer for a day and then were wrapped in silk mordanted in alum. My favourite results were from a bundle where the fabric was dry, the only moisture provided by the melting flowers.
It made an interesting repeating pattern, a sort of abstract floral print. It was intense purple until I decided to soak it in a bath of alum as a post-mordant. Then some of the colour floated away and the rest took on a greenish tinge.
I gather that all the pinks and purples are chemically anthocyanins. There's a good chapter about them in Dominique Cardon's Natural Dyes. Not the most stable of dyes but very interesting to play with. I stuck a dyed piece on the window to see just how light-sensitive it is.
There are a couple more bundles on the go. To be continued...