Why roses are red and violets are blue
February 6th, 2007 at 11:04 pm (Plants)
Today I finished the chapter on vegetables in “What Einstein Told His Cook 2”. One of the tidbits that stuck with me was the fact that (red) roses and violets both have the same pigment; it’s an anthocyanin that, like litmus paper, responds to pH with a color indicator. Rose petals are slightly acidic, so the pigment shows up as red, while violets are slightly alkaline and therefore appear blue. (Gosh, I shouldn’t have bothered buying that 100-pack of pH indicator paper; I’ve got 11 rose bushes outside!)
Apparently, the presence of anthocyanin also explains why the new growth on a rosebush is tinted red, but the older leaves are green; new growth that hasn’t yet begun producing chlorophyll is vulnerable to radiation from the sun, so extra anthocyanin is produced in the meantime, which protects it from UV.
Now I’m wondering: if I take a violet petal and drop it in some vinegar, will it turn red? Can I dye my roses with household chemicals? My roses are actually white, so no telling what would happen in different pH conditions (maybe nothing; the white could mean that they lack anthocyanin). I hear an experiment begging to be performed this weekend…
Edit: I may have to wait on this; I forgot that I’d just pruned all of my rose bushes down into skeletal stumps of themselves, with no blooms to be had.