What substance is used to lower the pH of water without creating a toxic environment for flowers?

Citric acid is an effective substance used to lower the pH of water while maintaining a safe environment for flowers. It is a weak organic acid that not only helps in reducing the pH levels but also does so without producing harmful byproducts. This characteristic is particularly beneficial in floral arrangements because maintaining a non-toxic environment contributes to the longevity and health of the flowers.

Additionally, citric acid has the added advantage of acting as a natural preservative, helping to inhibit the growth of bacteria in the water, which can otherwise cause the flowers to wilt prematurely. The use of citric acid is common in floral care solutions and is favored among florists for these beneficial properties.

Other substances listed may not have the same safety or efficacy in the context of floral arrangements. Acetic acid, while it can lower pH, is more potent and can be harmful to flowers in higher concentrations. Sodium bicarbonate and calcium carbonate actually work to raise the pH of water rather than lower it, making them unsuitable for the purpose of decreasing pH in floral care.