Hydrangeas come in pink and white around these parts, but I was first made aware of this flowering bush during my many summer vacations as a kid on Cape Cod. There all the hydrangeas (which seem to pop up in almost every front yard) are blue. It's not that pink is for girls and blue is for boys, but boy oh boy, what a beautiful baby. Not to make you blue too, but there's really no way to grow these strikingly cerulean blooms in your own garden, unless you assiduously treat your soil with aluminum sulfate or happen to have dirt that is highly acidic and rich in that mineral. We found six examples of Alluminum in OhioLINK, and one each of Alunimum and Alumimum. Don't stay mum about this typo and don't get me started on the way our British friends both spell and pronounce aluminium ("for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound").
(Photo of a blue hydrangea in Dalat City, Vietnam, by Nguyen Tan Phát, 2008, from Wikimedia Commons.)