Hydrangeas

Hydrangeas are living pH indicators. The color of the blooms are determined by the composition of the soil that they sit within. You've probably seen them in blue, or white, or pink before, and that's why. They are sensitive enough to soil composition that you may even find the same plant with different shades on different flowers... 

That makes me think about the vascular system of a hydrangea. If the same plant has different colored blossoms (even if it's pretty minor), then doesn't that mean that there are some parts of the plant that are being fed by some areas of the soil, and some that are being fed by others? Are there completely separate vascular structures in different parts of the plant? 

Interestingly, they bloom on old wood. Some people cut off the old dead flowers, thinking that they are helping the plant by pruning, but that's the most common culprit for not getting more blossoms the following year. Here's a sketch of a mophead hydrangea  flower that's a bit past its prime. Someone here in Pittsburgh knows to keep them on their stalks!