We observed that the red dye began to be noticed in the flower after about 30 minutes. The green one after about two hours and the blue one a slight change after two days. (I did recut the blue flower) Do you have an explanation for this?

In the name of science,
-  Ina O'Connor & Zachary Goldstein - Eugene, OR

Ina and Zachary, I've heard from other budding scientists that the red is absorbed faster than other colors. I don't have a good scientific explanation for this, but I do offer this hypothesis. Dyes are composed of different chemicals to make them different colors. The red dye apparently has a chemistry that is absorbed faster. Perhaps it is lighter in weight or dissolves faster than the other colors. I suspect it is the chemistry of the dye that contributes to its faster uptake than anything about the flowers.
  - Dr. Bridget Behe

Virginia, So much of flower longevity depends on the genetics of the flower (some last a day, others weeks) and the care the flower received. I suspect the yellow daisies are chrysanthemums and they will probably last longer than red roses. I hope you are using a commercially-prepared floral food in the vase water, and that you measured the amount of water you added to the vases. That will give the fresh flowers their longest possible life.
  - Dr. Bridget Behe

Nathalia, Scientists typically use a subject scale or rating for the senesence (death) of a fresh-cut flower. I would suggest that you also take photographs daily at the same time, so you have a record of how the flowers changed each day. Perhaps put a 3x5 card in each shot with the date so you can see by looking a the photo which day it is (Day 1, Day 2, etc.). Look for discoloration or browning of the petal tips and edges. This is where you will first see the signs of decline. It is easy to see on light or white petals, but you'll notice discoloration on any color of petal.

I would decide how much of the petal needs to be discolored or brown and give a small amount a 1 and total discoloration a 10. I would suggest you use several petals with the same type of lip balm and try to cover them to the tips. Perhaps our observation sheet from the Flower Activities Center would be helpful.
  - Dr. Bridget Behe

Nancy, No, it will stay that color. No change should occur. The dye is deposited in the petals and won't come out with the water in the process of transpiration.
  - Dr. Bridget Behe

Both my daughter and I would like to know why green was only a nominal change. Would it have anything to do with the chloryphyll in the plant? I appreciate any help that you could provide. Thank you.
-  Kylie - Condell Park, NSW

Kylie, It wasn't the chlorophyll in the plant that made a difference. The dye may not have started to go up the stem because you may not have remembered to re-cut the stem under water. It is critical to re-cut fresh flower stems under water to help restart the flow of water up the stem. Cutting under water is ideal since it will eliminate the air bubble that can be trapped in the stem, causing premature death of the fresh flower.

There also appears to be some difference in chemistry of the food dyes. I understand from others who have done a similar experiment with red dye that that dye color tends to be slowest in uptake relative to the other colors. So, there are some factors other than chlorophyll that play a role in the uptake of the dye, but not the presence of chlorophyll.
  - Dr. Bridget Behe

Pat, We have an experiment outline to help you do an experiment like the one you describe at our Flower Activities Center. It is Experiment #3. The challenge is getting the dye in a high enough concentration to see it. I would suggest using one of the small containers (full) of food coloring to 8 oz. of water. It will seem like a lot of dye, but the flower can handle food coloring.
  - Dr. Bridget Behe

Jasmine, The water temperature will influence how quickly the commercial preservative is dissolved and will play a role after that in the longevity of the flower. Warmer temperatures open buds and dissolve preservative faster than colder temperatures. However, you also need to consider the effect air temperature will have. The water temperature will adjust to the air temperature and air temperature and relative humidity will influence transpiration (flower giving off water).

If you can keep a cool water temperature in a refrigerator, that will help you to see the effects of cold temperatures on cut flower (rose) longevity. Keep the room temperature water at the air room temperature for your medium level treatment. The high temperature treatment will be a bit of a challenge. Hot water is easy to get but hot air temperature may not be. I would suggest you have a thermometer in the air (at bud height) and in the water for each vase.

Record the temperature hourly (during the hours you are awake) during the first day to track how temperature changes. After that, it should stay relatively constant. However, do record the temperature three or four times a day. Be sure to use a commercially-prepared preservative for each treatment and follow the directions (measure the water in each vase) on the package.
  - Dr. Bridget Behe

The room and ice colored the flowers the same time 5 1/2 hr. green, yellow then red. Heat - 6-6 1/2 hr blue first. Is it that the temperature surrounding the flowers have to be the same for this to work? Put in refrigerator? Also is it better to have newer food dyes to work with.
-  Melanie - Poughkeepsie, NY

Melanie, The air temperature will also play a big role in how quickly the water is taken up. Air temperature and relative humidity are the two factors that determine how much water a plant transpires. Water temperature would be the third factor affecting water uptake. Yes, using a refrigerator would help. It has a cooler temperature (helps to decrease transpiration) and lower relative humidity (acting to increase transpiration).

In a warmer, drier environment (such as a home in winter), transpiration would increase. I doubt the food dye will change much in a year on the shelf, but perhaps it's chemistry would change over a longer time period.
  - Dr. Bridget Behe

Brittany, Most of the water treatments you are using will be very similar. Why? Because they lack floral food or preservative which has a simple sugar for energy and a component to keep stem-clogging bacteria and fungi from growing rampant in the vase. I suspect what you are seeing is more a function of the pH of the water. Can you get some litmus paper and check the pH of each vase? It would be best to test the pH of the water right from the source (not when it has sat in the vase for a few days). Lower pH water is more readily taken-up by the flower and may be a bit longer lasting than the other treatments. There is probably no sugar or food source in the water.

If you had time, a water test would be a good idea. The results would show not only pH, but other mineral components like bicarbonates that affect plants and flowers in different ways. As for sources of information, you might try searching the Chain of Life web site as a guest. Search for cut flowers and water and you should get some great information.
  - Dr. Bridget Behe

Cherish, Osmosis is movement of water from a high concentration to an area of low concentration, usually referring to a difference in sugar or salt concentration. Diffusion is movement of water in a direction. Water moves into a plant by osmosis, but it moves up a plant by the pull created by transpiration. So, when the flower is cut from the stem, transpiration continues (no more roots, no more osmosis) and pulls water (and any nutrients dissolved in the stem) up the plant.
  - Dr. Bridget Behe

Stephanie, We have an experiment outline that you might adapt to include pH. It is Experiment #3 at our Flower Activities web site. You may also find the observation sheet helpful. You could incorporate pH into the experiment by adding different amounts of vinegar (weak acid) and testing the pH using litmus paper (still available at some drug stores) or a pool testing kit (if you or someone you know has a pool).

I would recommend that you mix three cups of water (room temperature) with a packet or two of floral preservative. Be sure you measure the water and use an appropriate number of packets, following the directions on the preservative package. Add 3 entire containers of food dye (same color) to the solution. Now, it is time to create some differences to make three different treatments. Pour 1 cup of water into three glass containers, marking one container (to which you add nothing) as the comparison solution. Test the pH of that solution.

Then, to one second vase, add a tablespoon of vinegar, and add two tablespoons of vinegar to the third vase. Test the pH of those solutions. Store all three vases in the same room (same air temperature). Before you insert white carnations into each vase, re-cut 1/2" off the bottom of each stem, while submerging the stem end under water. This will help restart the flow of water up the stem. In a warm room, you should be able to see some color changes within a few hours.
  - Dr. Bridget Behe

Hannah, Before 1943, pennies were made of a high percentage of copper. After that, the amount of copper was reduced greatly. When pennies were a high percentage of copper, some of the copper could leach out of the penny and into the water. Copper has an acidifying effect when dissolved in water. In theory, it could help make the water more readily taken-up by the flower and keep the growth of some stem-clogging bacteria and fungi down. Not nearly enough copper leached out of the penny and into the water to do any good. It is one of those home remedies that simply doesn't work.
  - Dr. Bridget Behe

Christine, The air temperature is one factor and the water temperature is another factor. I am surprised that the flowers in the refrigerator showed color before the ones in a warmer environment. I suspect water temperature was the cause. At an equal air temperature, flowers will absorb water faster when it is warm. It will absorb water more slowly at a cooler temperature.

At the same water temperature, you would expect to see a greater change in color in a higher air temperature. My guess is you had warm water temperature and then put it in a cool environment. For your third trial, you might consider allowing water to sit at room temperature overnight, then mix your "treatments" the next day, and then transferring vases into different air temperatures.
  - Dr. Bridget Behe

Joy, The bent neck you observed was a result of an air bubble getting trapped in the stem. When you re-cut stems under water, removing about a half-inch of stem, you can eliminate that air bubble. It won't travel up the xylem and get stuck, causing the flower head to drop over. Some people believe adding sugar to a vase can help extend the life of fresh cut flowers. It is very difficult to get the right amount, since too much or too little will cause disappointing results. You probably had too much sugar to the volume of water. The best solution to use is a measured amount of water and a measured amount (or one packet) of commercial floral preservative.

Yellow roses are fine to use and the stem length won't play a role in whether the flowers lasted or not. We have a similar experiment outline at our Flower Activities Web Site that has some additional information.
  - Dr. Bridget Behe

Kari, The soda, which contains sugar, provides a source of food (or energy) for the flower to continue to grow and develop. The challenge with soda is that it is difficult to get it in the right concentration to help extend flower life. You observed this indirectly because your friend had a negative result when you had a positive one. There is some more information that you may find helpful in Experiment #3 at our Flower Activity Web Site.
  - Dr. Bridget Behe

Gabrielle, Some of your results can be explained by the concentration of dye and sugar in the water. More water was taken up in the vase without sugar. This suggests that the concentration of sugar was so high, that water was actually pulled out of the flower rather than being taken up. Water will move from an area of low concentration (of salts or sugar) to an area of high concentration. In this case, some water may have actually moved from the flower (low concentration) to the vase (high concentration). It stayed fresher longer because you supplied it with a source of energy (sugar) that was absent in the water & dye vase. More water was taken up in the vase without sugar, and was transpired through the petals. The water can move out, but not the dye. So, the dye was deposited in the petals and you were able to see it through the petal tissue (because there was not color originally in the flower). You didn't know it, but you learned about water potential!
  - Dr. Bridget Behe

Liliac, Flower color doens't cause any change in flower growth. Flower color is a function of the genetic make-up of the flowers, mainly to attract attention of pollinators. Flower growth is controlled by light (intensity, duration, and light color or wavelength), temperature (air and soil), and water.
  - Dr. Bridget Behe

Kinross, The flower will lose and absorb water based on surface area. The flower has the most surface area has the greatest potential to take up water. You can have flowers in those species of different sizes, but my educated guess would be the gerbera.
  - Dr. Bridget Behe

Kaydee, Baking powder won't extend the life of a fresh cut flower. In fact, if the particles are large enough, it can clog the vessels that take up water, decreasing the life of the flower. You will want to visit our Flower Activity Center and download experiment #1. That file contains some great information about home remedies that do (and don't) extend the life of fresh flowers.
  - Dr. Bridget Behe

Amanda, Yes, a dandelion makes its own food! The miracle of photosynthesis enables plants to take water and carbon dioxide (we humans exhale this) and, in the presence of sunlight and a green pigment called chlorophyll, combine them and make a simple sugar. People and animals can't do this, only green plants. Read more about this at our Fun Activity Center, especially Experiment #2.
  - Dr. Bridget Behe

Lairy, Vinegar is a weak acid and, when added to vase water, can reduce the growth of some stem-clogging bacteria and fungi. It doesn't have a sugar source (food for the flower) so it makes a poor floral preservative. Learn more about different home additives and why they also make poor floral preservatives at our Flower Activity Center (especially see Experiment #1).
  - Dr. Bridget Behe

Casey, The can die from using bleach in the vase water. Today, most bleach contains both an acid and lye. If much more than one teaspoon is dissolved in a quart of water, it could cause problems (burn) for the flowers. Be very careful when handling bleach as it is a dangerous chemical that can burn just about any surface it touches. Remember to add bleach to water not water to bleach (to reduce splashing of the concentrated chemical). If you dissolve about a teaspoon in a quart of water, it can reduce the growth of stem-clogging bacteria and fungi, but since it has no source of food or sugar, it makes a poor floral preservative.
  - Dr. Bridget Behe

Belinda, Salt is toxic to fresh cut flowers. While there are some salts dissolved in the cells of plants, putting fresh flowers in a solution of table salt and water will cause some of the water to leave the cells in the flower. Of course, this is not what we want to have happen. The flower is comprised mostly of water and having water pulled out of the cell won't extend life but will reduce it.

What does that have to do with ethylene? Ethylene is a colorless, odorless naturally occurring gas that horticulturists consider a plant hormone because the presence and concentration does affect several aspects of plant growth. Ethylene is given off by ripening fruit, like bananas and apples, but also by combustion engines as a by product of combustion. Ethylene is given off naturally when a flower begins to die or senescence. Once ethylene is present in a small amount, it triggers the flower to produce more, hastening the dying process. This is why we never store fresh cut flowers with fruit - it will help them produce their own ethylene and die faster.

Back to the salt issue. Once the cut flower is put in salt water and begins to die, it will begin to produce ethylene. As the flower begins to produce a little ethylene (because the salt water is toxic and the flower is not growing but dying), the presence of some ethylene will trigger the flower to respond by making more - hastening death. So, salt water can indirectly (through the ethylene response) and directly (drawing water out of the cell) hasten fresh cut flower death.
  - Dr. Bridget Behe

Kerri, I suspect the stem diameter was large in size relative to the petal tissue. So, the tulip could take up more water, appear to do this quickly since the tulip petal tissue is thin and there aren't as many petals as there are in the other flowers. Be sure that air temperature and water temperature didn't play a role in the difference. Warmer air and water are taken up faster than cooler air and water.
  - Dr. Bridget Behe

Dear Dr. Behe,
How can I grow my own green carnations and chrysanthemums please?
-  Lorna

Lorna,
It may be easier to change the color of white carnations and chrysanthemums than to grow them yourself. There usually are a few cultivars of chrysanthemums that are off-white (not stark white) that might be considered a pale green. You can change the color of cut flowers by using food dye. Select white or light colored flowers. I like to use standard carnations or even miniature carnations for this experiment. You could also use white or light colored chrysanthemums.

Select identical vases to hold the different colored solutions. The vases should be clear glass or plastic. Before you add any color, mix a gallon of floral preservative solution. This will help the flowers last longer by providing them with a food source and a biocide to reduce the growth of stem-clogging bacteria and fungi. Mix a floral preservative solution by obtaining a number of packets (8-16) of floral food from the place you purchase flowers. Be sure to follow the directions for the amount of water to add to the packets. Also, be sure to use warm water.

Mix the packets and the measured amount warm water in your clean milk jug. Stir to mix well. Next, pour 8 oz. (1 cup) of the solution into each clean vase. Into each vase, empty one whole container (about 0.25 oz.) of food coloring of your color choice. Stir to mix. Have a small bowl filled with warm water sitting alongside the vases or glasses. Be sure that you re-cut a small amount of the stem off while holding the end under water. This will also help to restart the flow of water up the stem. Simply use sharp shears or scissors and snip off the bottom 1/2 inch of the stem while holding about 2-3 inches of the end of the stem under water in the bowl. Then, transfer the flower to the prepared glass or vase.

You will need to keep all the flowers in the same room to keep them under relatively the same temperature and light conditions. In a 70°F room, you should see some color change within a day or two. You will probably need to add floral preservative solution in a day or so, as the level will go down in each vase. Add the same measured amount (about 1/4 cup) to each vase so you dilute the color equally in each vase.
  - Dr. Bridget Behe

Dear Dr. Behe,
What is the growth of a carnation with Advil, Aleve, Tylenol, Aspirin, Ibueprofin, Excededrin P.M., and water?
-  Tinkerbell - Santa Ynez, CA

Tinkerbell,
I hope your science project doesn't give you a headache! With all those pain relievers, you would almost think the flowers had a headache. They don't. Neither do any of those pain relievers, when crushed and added to water, help the fresh cut flower. Flowers need a food source and the pain relievers don't have any sugar in them to provide any food for the flower. Also, the small grains that don't dissolve can quickly clog the xylem or water conducting tubes/vessels that carry water up the stem. Water is needed, but doesn't have any food for the flower either. I would suggest you try your experiment after reading our outline and be sure to use a commercially prepared preservative as one of your treatments.
  - Dr. Bridget Behe

Dear Dr. Behe,
How does Baking Soda In the Cut flower's water affect it's growth?
-  Sam - Franklin Park, IL

Sam,
Baking soda (sodium bicarbonate) will probably clog the stems, keeping much needed water from going up the xylem. That's bad, but it gets worse. Even if water could go up the stem, there is no food for the flowers in baking soda, either. The flowers probably won't last too long.
  - Dr. Bridget Behe

Dear Dr. Behe,
I'm doing a science fair project on what solution flowers last longer in and I was wondering, what is in those packets that the florists give to you when you buy flowers?
-  Alison - Seaford, DE

Alison,
The companies that make professional preservative consider the ingredients "proprietary" and don't list them on the package or tell you when you call (as I have). I do know that the packets contain a mixture (that's what is proprietary) of a simple sugar (usually glucose or sucrose) and a biocide. The biocide reduces the growth of stem-clogging bacteria. The packets are very effective at prolonging the life of fresh cut flowers and I highly recommend consumers use them and especially follow the package directions. Too much preservative dissolved in water is as bad as too little (which happens very often), so following the directions is very important.
  - Dr. Bridget Behe

Dear Dr. Behe,
How can you change the color of a rose? Some people say that if you put a certain color of food dye in a glass, and you put the stem into the food dye, the rose will change to whatever color the food dye is. Is that true?
-  John - Torrance, Ca

John,
You can change the color of light-colored or white flowers, including roses. They need to be fresh flowers. Roses that are full-blown or very open won't take up as much water (and color), so their color will be hard to change. Dark colored roses are tough to change because they are so dark. Water flows up the flower stem through special tube-like vessels (almost resembling a straw) called xylem. You can follow water being taken up to the petals, if you could see the water. You can see the water travel when you add food coloring to the vase solution.

Paint won't work as a dye for flowers. It will be toxic to the flowers or clog the stem. Food color works well because it is safe for the flowers. Select identical vases to hold the different colored solutions. The vases should be clear glass or plastic. Before you add any color, mix a gallon of floral preservative solution. This will help the flowers last longer by providing them with a food source and a biocide to reduce the growth of stem-clogging bacteria and fungi.

Mix a floral preservative solution by obtaining a number of packets (8-16) of floral food from the place you purchase flowers. Be sure to follow the directions for the amount of water to add to the packets. Also, be sure to use warm water. Mix the packets and the measured amount warm water in your clean milk jug. Stir to mix well.

Next, pour 8 oz. (1 cup) of the solution into each clean vase. Into each vase, empty one whole container (about 0.25 oz.) of food coloring of your color choice. Stir to mix. Have a small bowl filled with warm water sitting alongside the vases or glasses. Be sure that you re-cut a small amount of the stem off while holding the end under water. This will also help to restart the flow of water up the stem. Simply use sharp shears or scissors and snip off the bottom 1/2 inch of the stem while holding about 2-3 inches of the end of the stem under water in the bowl. Then, transfer the flower to the prepared glass or vase.

You will need to keep all the flowers in the same room to keep them under relatively the same temperature and light conditions. In a 70°F room, you should see some color change within a day or two. You will probably need to add floral preservative solution in a day or so, as the level will go down in each vase. Add the same measured amount (about 1/4 cup) to each vase so you dilute the color equally in each vase.
  - Dr. Bridget Behe

Dear Dr. Behe,
I did your experiment of the florist additive, sugar, and the water. I concluded that the florist additive worked the best, then sugar, then the water. The water was the first to wilt I used daisies. Do you think that my experiment would nave turned out different if I had used a different flower?
-  Tracey - Virginia Beach, VA

Tracey,
Most of the time, the commercial preservative will work best. Why? Because scientists helped to mix an ideal food source but keep the nasty stem-clogging bacteria and fungi from growing. Yet, there are lots of variables in any experiment. You could do the experiment 10 times with daisies of different ages or put daisies in rooms with different air temperatures or not re-cut stems under water and get some different outcomes. I suspect, however, that you followed our recommendations and you probably would come up with the same results using another flower.
  - Dr. Bridget Behe

Dear Dr. Behe,
What are some facts about carnations? I am doing a science fair project about them. What are some details? I know they take about four hours to be done with the whole thing, but what is the hypothesis and conclusions?
-  Sarah - WA

Sarah,
Carnations are in a beautiful and diverse plant genus called Dianthus. According to Hortus III, a book containing a description and background of nearly every cultivated plant, there are about 300 species of annual or biennial or perennial plants in this genus. They were originally from the geographic area where Europe and Asia come together (called Eurasia) but are also found in South Africa. They come in lots of common names from carnations, to pinks, to sweet William. Some have a light fragrance but others don't.

The four hours you mentioned might be the length of time it takes for them to show they've taken up dye (if it is in a high enough concentration). Certainly, they last for many days longer than four hours as they are one of the longer-lived fresh cut flowers. My hypothesis about dye being taken-up by flowers might be the length of time (instantly, 1 hour, 2 hours, etc) or where the dye will be see first (petal tips, petal base, stems, leaves, etc). Your conclusions would then be based on whether what you observed matched your hypothesis (or not). The real tough question to answer is why did (or didn't) your observations match?
  - Dr. Bridget Behe