Effects of Color Dye on Plants

All of the chemicals that go into consumable products inevitably wind up in the natural environment. Dyes make up a large portion of these chemicals; they're added to food, laundry and dishwashing detergent, body soap, clothes and paper products. Though plant-based dyes, inks and food colorings are generally assumed non-toxic, it's still important to gauge the impact of their entering the water supply that feeds local plant life.

Effects On Cut Flowers

A common biology lesson or science fair project is to place cut flowers in a series of vases and add water-soluble food coloring to the water in each one. Within 6 to 12 hours, the tint will have crept up the stems and into the leaves and flowers, clearly demonstrating the path water takes through the plant's system. The dye only affects the plant cosmetically, changing its appearance but not its health or lifespan in the vase. Dyed cut flowers drink and wilt at the same rate as cut flowers in undyed water.

Effects On Growing Plants

Adding food-based dye to the water supply has no significant effect on growing plants, either. Since food coloring is non-toxic, it doesn't poison the plants. Nor does it substantially benefit them; the food content of the dye isn't sufficient to act as fertilizer. Given enough dye in the water consistently over a period of time, food coloring will alter the plants' appearance.

Effects On Submerged Aquatic Plants

Though food coloring isn't poisonous, dye can harm plants another way: by blocking the sunlight. Submerged aquatic plants can only grow in "the photic zone," the region where sufficient light penetrates the water for plants to survive. Dyes make water more opaque, thus reducing the photic zone to a shallow area near the surface. This can happen naturally due to phytoplankton bloom or to accumulated tannic acid from fallen leaves. Some pond owners do this deliberately, tinting the water with dark blue aquatic dyes throughout the spring and summer as an ecologically responsible way to suppress algae and other aquatic growth without poisoning livestock, fish, or nearby wildlife.

Effects in Compost and Mulch

Paper products break down easily, their inks running off into the soil. People increase the rate of this process when they compost shredded newspaper or use it for mulch. The inks used in printing newspapers today are mostly soy-based and, unlike the petroleum-based inks of yesteryear, will not harm plants. Colored paper and inks have been a cause for concern, in that they may contain heavy metals, but, as it turns out, where heavy metals are present, the concentration is far too low to present a significant risk.