What Does Food Coloring Do to Plants?
- This particular urban legend says that adding a few drops of food coloring to the water that's used to water your plants or the water that you put in a vase that displays cut flowers will either foster healthy growth or gradually change the color of the plant's blooms over several generations (or both). The idea is that the plant will "drink" the combination of the water and the food coloring rather than filtering out the food coloring in favor of the water alone.
- This myth does have a bit of science on its side--plants use differences in water pressure to transport water that the plant drinks from the soil around it and from the roots where it is stored up to the leaves, where it is used for further plant growth. The more water sent to the leaves from the roots via transpiration, the greener the leaves appear, so it stands to reason that were plant leaves to drink water and food coloring, the food coloring would gradually tint the color of the leaves.
- Science fairs often feature this experiment; a student will add food coloring to the water used to water a white plant and compare it to a control group of white plants that were watered with water alone. If performed properly, tinting of plant leaves will appear, but other than that, the food coloring really has no effect whatsoever on plant growth. Food coloring is non-toxic, so adding it to water will not threaten the health of the plant, but it also does not contain any nutrients that the plant needs in order to grow, so adding it will not help the plant nor harm it.
- The best way to determine on your own how useful this technique is is to experiment on your own plants. White flowers probably yield the most noticeable results, but remember that it may take several seasons before the plant is noticeably tinted. If you cut the flowers and put them on display in a vase, don't be surprised if some of the food coloring leaches back into the water and tints the water in the vase.