It’s easy to make colored flowers using a simple science project. The project is safe and easy enough that kids can try it. You get beautiful colored flowers while applying several scientific concepts, including osmosis, capillary action, cohesion, transpiration, and the function of xylem in plants.
How to Make Colored Flowers the Easy Way
All you really need for making a colored flower is a flower and some colored water. But, some flowers work better than others. The chemical you choose as a dye also matters. Ideally, use white or pale freshly-cut flowers. Carnations and daisy work best. Flowers from woody plants, like roses, also work but take longer to change colors. The healthier the flowers are, the better they’ll pick up the color. Ordinary food coloring works great as a dye because it is water-based. Avoid oil-based dyes because they’ll just float on the water surface so the flower won’t absorb them.
- Fresh flowers
- Warm water
- Glass, vase, or cup
- Trim the stems of the cut flowers at a 45° angle. Ideally, make the cut underwater so you don’t get air bubbles on the cut end of the stem that block water absorption. The fresh, angled cut helps the flowers absorb water and keeps the stem from sitting flat on the floor of the glass.
- Add warm water to the glass. The warm temperature helps color the flowers more quickly. Add a splash of vinegar and spoonful of sugar. If you want exact measurements, use 1 teaspoon of vinegar and 1 teaspoon of sugar for each 200 milliliters of warm water. Technically, you don’t need the vinegar or sugar, but they help keep the flowers healthy. Vinegar is a natural antimicrobial agent that also makes the water more acidic, while sugar gives the flower nutrients.
- Add food coloring to the glass. You need quite a bit of dye (probably 25-30 drops) because the flower does not absorb all of the water.
- Place the flower in the colored water. The edges of the petals pick up color within a few hours. It may take a full day to completely color the flower.
How to Make Two-Colored Flowers
Now that you understand the basic technique, try using two dyes.
- Trim the flower stems with an angled cut. This time, carefully split the stem from the cut end up toward the flower.
- Add warm water, sugar, and vinegar to two glasses. Choose short, narrow glasses so you won’t have to separate the split stem too much.
- Add one color of food coloring to one glass and a second color to the other glass. Keep in mind the colors will blend a bit where they meet in the petals. For example, if you use blue food coloring and yellow food coloring, you might see some green petals.
- Carefully open the split on the stem so one half is in one glass while the other half is in the other glass.
How to Make Tie Dye and Rainbow Flowers
Splitting the stem into even more sections gives the flowers a tie dye or rainbow effect. This is one of the methods of making rainbow roses.
The Science Behind Colored Flowers
Plants drink water through a process called transpiration. Water evaporates from the petals, leaves, and stems of the flowers. Most of the water leaves through tiny openings in the leaves and stems called stomata. Water molecules stick to another another through cohesion. Basically, hydrogen bonds between water molecules attract them to each other. So, when water exits through stomata, it pulls more water up the stem.
Water and dissolved nutrients (and dye) move through the xylem in the stem. The xylem is not a long open tube, like a straw. Instead, it consists of stacks of tubes connected by narrow openings. These pores make the xylem semipermeable. Small molecules move through the xylem, but large ones don’t. So, the movement of water up the xylem is by osmosis rather than simple diffusion. Capillary action involves the cohesion of water molecules and adhesion of water to the xylem wall also plays a role. Water rises up in the xylem above ground level because the small diameter of the xylem bundles. But, the positive pressure of nutrients from the roots (or dissolved sugar in the glass) and the negative pressure of transpiration are essential for getting water all the way to the tips of the flower petals.