In nature, we can directly observe shifts in habitat for different organisms. Study the image of the hydrangeas that are so often used in elegant landscaping. The light purple hue comes from soil that is nearly neutral. Pink hydrangeas result from acidic soil and blue flower petals result from basic or alkaline soil conditions.

Question

If a landscape architect opts for the following changes what result will become visible in the blooms?

(2 points)
Blue (basic/Alkaline) Pink (Acidic)
Some bushes in a garden are already blue, but some have faded to light purple and even pink on one side. The landscaper adds lime (calcium hydroxide/oxide compounds) to the soil. Which color will result in the flowerbed?

All the hydrangeas in a certain flowerbed are blue and the landscaper's apprentice adds sulfur and aluminum sulfate to the soil by mistake, then waters heavily. What happens to the color?

Answer 1

1. If the landscape architect adds lime (calcium hydroxide/oxide compounds) to the soil where the hydrangeas have faded to light purple and even pink on one side, the soil will become more basic (alkaline). As a result, the color of the blooms will shift towards blue. Therefore, we can expect that the flowerbed will predominantly display blue hydrangeas.

2. If all the hydrangeas in a certain flowerbed are blue and the landscaper's apprentice mistakenly adds sulfur and aluminum sulfate to the soil, this will increase the acidity of the soil. Since blue hydrangeas thrive in basic (alkaline) conditions, lowering the pH will cause the blue hydrangeas to change color. Consequently, we can expect the blooms to shift towards pink or even light purple, depending on how acidic the soil becomes.