Great article. I always laugh when a customer asks for purple petunias since 9 times out of 10 they want "Blue Petunias", which to our eyes is dark purple and the "Purple Petunia" is actually a Magenta colour.
Last year I bought the Black Velvet petunia. Very different and really looked like black velvet. One hot day we had a short down-pour which cooled things off very quickly. All the open flowers of the Black Velvet turned a wine colour. I had to wait for new blooms to see the black velvet colour again.
I put Epsom Salts around all my roses once a month throughout the growing season. It is amazing how strong the colours become in comparison to what my gardening pals say about their same roses. The cool night temps do play a factor and the colours are always stronger with cool temps. This is Folklore Rose
