Starting with seeds is probably the most effective way (and cheapest) way to go if you want to see obvious change over a 3 week period.

Beans have always been a traditional choice for these kinds of science projects.

You can always consult your local nurserymen about which seeds grow the fastest or just go through each packet of seeds and find which ones germinate the fastest.

Hope this helps!

R

THanks for the quick response R!

Personally I thought the same thing about the seeds. I thought that would give the most accurate results too as they are all starting from the same point. Who knows if one of the plants that he buys has a more mature root system or something else that might affect the growth. The teacher did not want any from seeds though. :c( My son said her reasoning was that three weeks might not be enough for some plants.

Frankly, 3 weeks is precious little time to see easily detectable changes unless one does start from seed. And I agree that beans would be a good seed choice. Others might be corn or radishes.

Further, I think that poinsettias would more likely decline than grow.

So perhaps the teacher can suggest a plant or two which might work.

Beyond that, I just did a search with the phrase "science project compare plant growth" and found that various sites list projects by grade, such as grades 1-4, and on so on.

Perhaps a different search using only "science project" would be more useful.

I'm not trying to be negative here, but as a former science fair judge and working scientist (until this past August, in any case), I don't think that this is a good project.

The best projects are not found in books of science projects or on websites of the same. The winning projects involve things that the child observes in his or her world: riding bicycles, throwing things, whether dog mouths are really clean or not, whether phones are germy, what makes the reception go out on your radio or TV, how long it takes for leftovers to go bad, etc.

The next step is to develop a systematic approach to answering the question. There should always be three (or more) replicates of each sample/subject and condition, and careful data recording and observation are important.

But if you are locked into the plant growth experiment, I'd use beans, corn and radish seeds, three pots (I'd use dixie cups) of each type of seed per light regimen. I'd also do a series of plants that received no light except when watering or checking: just put a box over the no-light plants. If possible, compare natural light to incandescent light AND fluorescent light. It's also important that all seeds receive otherwise identical treatment: be sure each pot or cup is the same size, be sure that they contain the same weight of the same potting soil, be sure each cup receives the same amount of water until growth begins (then you can increase or decrease to prevent rot and fungal diseases). Be sure the seeds in each case all LOOK identical to the naked eye. Don't plant one itty bitty bean seed and one gargantuan bean seed. Be sure that within each type of seed, all are planted at the same depth. You could use a pencil with a bit of tape, an inked line or a bite line to make sure that each seed is at the same depth. Radishes don't need to be planted as deeply as corn seeds, which don't need to be planted as bean seeds.

Measure growth of all plants from the top of the soil to the top of each plant. It's easier to use centimeters when doing calculations. Daily recordings are probably best. It's also important to make sure that as much as possible, the plants receive the same amount of light. Switch plant positions more than once a day, if possible. Measure the soil temperature (a rectal thermometer or an outdoor weather thermometer would probably work okay). It's important to keep that constant between treatments, too. You can use a fan to cool the hottest set of pants off.

The other thing that's important to do is to ask why a particular type of light works better or worse than another. Think of ways you might want to test what kind of light is best: can you get hold of a light meter (camera stores usually have them, as do some cameras) to test light intensity? Is the light different in any other way? What happens if you change the "color" of the light with colored cellophanes?

There is stuff online about the characteristics of the different kinds of light and how it can affect plant growth. Consider that information when suggesting future experiments. (You don't have to DO those experiments--but thinking about what you would try is important to note on a science fair project).

I bet you didn't think this could swell into a monster project without much increase in equipment required, but that's what good experiments do. Don't expect a lot of guidance from your son's teacher, because most teachers aren't scientists or science fair judges. Some (maybe not your son's, and certainly not all) elementary school teachers are incredibly weak in science.

Don't forget to follow the format the teacher gives for the report:

First comes an introduction, with a short description of the background that led to this experiment and a statement of the question (the hypothesis) to be answered or tested. This covers why you are doing the experiment, and "Mrs. Kerbopple made me" doesn't cut it.

Next comes the "materials and methods" section. Here you would list the brands and types of seeds used, the brand of paper cups (cheaper than pots) used, their size, and what kind of cups they are (waxed/unwaxed/plastic), the brand of seed starting soil used and what it contains (that should be on the package), how much soil (preferably in grams, but ounces are okay because what's important is that all soil amounts weigh the same) was used in each pot, how much water was added and when, any fertilizer use, how much and when (I wouldn't bother), the brands and wattages of any light bulbs used, the light intensity data if you can get it, how many hours the lights were on (preferably sunup to sundown), and what temperature the soil in the cups was at. Use the same watering can for all the pots so that water temperature is the same, too. Otherwise you have to check each time you refill the watering can (or jar or glass or whatever). Be sure to note at what depth each seed was planted relative to the top of the soil. Record the date and time every time you checked your plants.

Now you present your data, preferably in graph or table form (or both): This is called the "Results" section. It should contain all measurements of the plants heights as well as the dates and times of those measurements, and the number of days after planting to germination. Taking photographs comparing the plants' different treatments is always a nice extra. Place the three bean plants raised in a sunny windowsill next to the three plants raised under a light bulb, for example. Be sure to make up a caption explaining the picture. You can plot the plants' height against the number of days since planting and since germination to make nice graphs. You can do some statistical analysis using Excel and make nice bar graphs.

The next section, "Conclusions", should answer the question or hypothesis from the "Introduction" section using the data from the "Results" section. It's perfectly okay at this point to write "There was no difference between the two (or more) treatments with any of the plants. I think this is because ..." And if all the plants get killed by damping-off, or cats wrestling on the pots, write that, too. Chances are, though, you will see differences. Try to explain why those differences exist and how you would test your explanation (a new hypothesis).

Last of all comes a bibliography. Don't just include the handout for the assignment. Look some stuff up in a book or on the web. Use the seed packets themselves as the source for the bibliographic entries for how you planted the seeds, and why you planted them the way you did. Don't just blindly list bibliographic references: it's best to use footnotes to supplement statements in the introduction and conclusion, plus a bit in the methods/materials section.

Lisa

My daughter is doing the same type of project as your son (although she has more time than he does). She planted cherry tomato seeds on December 18 in three different light situations and this is what they look like now.

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The difference in growth was noticeable within a couple weeks of when she planted them and is just getting bigger. None of the plant nurseries had any seeds this time of year, but Home Depot had lots.

Juliet

Wow... Thanks Jean, Lisa, and Juliet. Wow Lisa. Thanks for taking the time to write that very long and informative post! That is the kind of experiment I would like him to do.

I agree 100% about starting from seeds. When my son asked his teacher about starting from seeds she said that it would not work since the experiment is only 3 weeks long and that he could not measure the plants growth progress while it was still under the surface of the soil. I am not going to ask him to argue with the teachers wishes. Perhaps she found that 6 weeks in the past usually meant incomplete experiments due to dead plants? Who knows.

Hopefully he will see some results.

Thanks everyone for all of your help!

Ken

Ken - it's too bad that you can't use seeds - I'm surprised at how much my daughter's tomatoes have grown and it will be 3 weeks tomorrow since she planted the seeds. Before we decided what plants to use, we talked to a woman who took care of houseplants in one of the nurseries we went to and she said ivy grew fastest.

Juliet

Another comment on science fairs:

There's usually a time when the child presents his project to the judges. With our two children we allowed plenty of time and house space to make clear, colourful, informative posters. The posters were fabulous long term learning experiences. They both learned which information was most important, how to make clear, simple, artistic presentations and also how to speak intelligently to others about their work. We practiced a lot at home in advance. Now 31 and 36 years old, they still remember each and every science fair and the bonding with Mom and Dad...not to mention the science! Both work in fields where public presentations are important.

Okay--revising the experiment for use of plants (poinsettia or ivy): I think that even the poinsettia would show changes during the three week period, but I would be worried about leaf drop/loss with the poinsettia. You probably should do the following during the experiment:

1) count the number of leaves on each plant. If you are within a leaf or two, remove a leaf or two from the leafier plant near the bottom (the worst-looking leaves) to make the number even. Do this before you start the experiment.

2) Weigh the plants. The analysis might not show any differences between the two regimens in terms of net growth, but when divided by weight might show a difference. Try to make sure that the plants start with approximately equal soil moisture levels--you could use a soil moisture meter to make sure that this stays the same. Weigh the plants every time you measure them, and if you can measure soil moisture, do that every time as well.

An inexpensive proxy for a soil moisture measurement would be to place a square or circle of paper towel or coffee filter on to the surface of the soil, and measure how long it takes for the paper to become damp.

3) The place where you should see significant change is not perhaps in overall length of the plants, but the length of the stems between leaves (length between leaf nodes). To measure this difference effectively, put a small piece of twist-tie around the bases of the leaves you want to measure between so that you can find those leaves and stems again. Don't make the twist-tie very tight. You could use yarn and tie it loosely, as well. Don't make the tie or yarn pieces any bigger than absolutely necessary. If you wanted to be really systematic, you could get those little jewelry price tags that attach with a thread loop and number the tags. For your introduction and conclusions, you will want to look up information on the types of light (just like I mentioned with the seed experiment) and information on "etiolation". Etiolation, or lengthening of the stem between leaf nodes is what you would expect to see with a lack of light or with the "wrong" kind of light.

The suggestions I made about using a light meter still hold, because another question that should be asked is whether it's the distance to the light source that may cause lengthening.

By weighing the plants at each point, you can also control for additional biomass (plant growth) production. My guess is that the plants in both groups would be about the same--but that the stems and leaves under one treatment would be thinner and longer. If you really want to have fun with the biomass portion, at the end of the experiment, compare the differences in the plants visually (and note those differences), then dump the plants out of their pots, rinse the plants clean of as much soil as humanly possible, and leave the plants to dry. THEN weigh the plants and compare the masses. Which treatment, if any, produced the most biomass? Was there any difference in the size of the root mass? I realize that with the exception of weighing, these observations are more subjective and qualitative, but it could lead to more sensible data analysis and better subsequent experimental proposals. Don't forget to compare the color and quality of the leaves in both plants: one group of plants will probably have leaves that tend more toward yellow, and one more toward green. You could use something like a process color chart or embroidery floss sample card to describe the differences in color more accurately.

I hope that you aren't absolutely overwhelmed by all this--I get into science and things just take off...

If one need to be completely "scientic" about the whole project, then ljrmiller is right - you need to ensure that the experimental plants share the exact same conditions of duration of light, temperature, watering, fertilising, etc. But for all intents and purposes, this is a school project - in which case, I have to ask - at what level of schooling is your son. We surely can't expect the same degree of scientific exactitude from a studen in elementary grade 2 versus high school grade 11?

Discovery is best done in concretes steps. For an elementary student at the lower grade levels, isn't it sufficient to just post the less complicated hypothesis "the seedling grown on my mom's kitchen window sill is no different from the seedling grown under the fluorescent lamp"? Shouldn't the emphasis be more on discovery and fun?

If your son is in grade 11, by all means, go for what ljrmiller says!

I used to teach 6th grade science (I still teach, just high school math now) and I found that I could get morning glories (and peas)to put out 3-4 inches growth (from seed) in a week or less.

I would soak the seed in water (with a little fish emulsion) for 1-2 days (in this time seeds would swell, split). I would plant the most vigorous into peat pots (or small dixie cups with potting soil) on Friday before school let out. By Monday I would have significant growth (it helped that my room was always very warm too!). By the next week the kids never could believe that I didn't slip in plants I had been growing at home.

There were 6 of us teaching sixth grade at that school and we used to make a race of it (in growning the plants). The kids would swear to the other teachers that we did all the planting the same day their kids had done it (the Friday before) and used to love how much further ahead our always were. We'd keep it a secret that we soaked our seeds first.

~Chills

I was going to suggest sweet peas.

Cactusjoe, I see your point, but I'm writing not only from the standpoint of a research scientist, but a science fair judge. As a scientist, the details and attention to detail are essential. It doesn't help science or scientists to have a kid who is excited about science without substance. Personally, I think the substance is fun, that the detail is fun, that the complexity is fun. I would never say that science is easy, but that it's challenging, and that even the hard parts are fun. I might even go so far to say that the hard parts are the best, the most fun parts. Well, most of the time...when things go badly, things really stink.

I'm also writing as a science fair judge, pointing out the things that make for winning entries. Especially for the lower grades, it's a demonstration of the entrant's ability to consider the question in depth and to go beyond mere assignment that make one of dozens of plant growth and light experiments stand out. Yes, this is most likely "only" a science project, but why not get as much as possible out of it?

I was also trying to suggest ways to think about the experiment, how the experiment should be done, and how to anticipate and analyze the results.

I don't want to repeat what's already been stated. But I agree the teacher should suggest which plants or seeds the children should use. Leaving it up to them isn't really fair and there are some seeds which germinate quite quickly. To me that would be a better experiment because each plant would be starting at the same point.

But since seeds are out of the question, as stated, ivy definitely is the faster grower of the two. If you can find them in nurseries now, marigolds, sunflowers and most annuals are very fast growing and might be better choices. I did a little research for you if your son takes an interest in horticulture. He might enjoy growing these in the spring. Good luck!

Very fast germinating flower seeds are:
Centaurea (bachelor 's buttons)--7 to 10 days;
Dianthus (sweet William)--5 to 10 days;
Rudbeckia (gloriosa daisy)--5 to 10 days;
Ageratum--6 to 10 days;
Cosmos--5 to 7 days;
Sweet alyssum--8 to 15 days;
Zinnia--5 to 7 days;
Mexican marigold--5 to 7 days.

Vegetable seeds:
corn--5 to 7 days;
cucumber--7 to 10 days ;
lettuce--7 to 10 days;
watermelon--5 to 7 days.

The issue of parental guidance and help always arises at science fair time. "It isn't fair!" echoes at these events. "I'm a single Mom! I don't have time!" "I don't know anything about math and science." "I can't afford the materials."

My point of view is that giving our kids advice and guidance is what parents are for. DOING the project is up to them, but starting them early, helping collect materials and reviewing it and listening to them practice their presentation before the magic day is important.

If they learn things from the experience, their project is a winner and their parents should be proud. Not everyone wins a medal.

Gardenbug, I totally agree. I'd also like to point out that I and the other judges in my group routinely scored science fair entries lower if it was painfully clear the parents had taken over the project. Parental help was okay, and even to be expected in the lower grades, but sometimes the cruder poster won over a more polished entry simply because mom's and/or dad's hands were all too evident.

Kids, especially in the lower grades, usually have a very direct use of language, and if the child was responsible for the experiment and the analysis, it showed through.

I remember one experiment that didn't take a prize, but we all thought the kid had tremendous potential. The poster simply had the word "meat experiment" at the top, and three jars containing meat and some kind of liquid. The liquids chosen were pepsi, water and clorox. Even though there was no further explanation, it was clear that some kid had heard that pepsi dissolves your insides and set out to prove or disprove it.

Had the entry contained a simple introduction explaining this urban legend, some information on how the question would be tested and analyzed, and a conclusion ("Pepsi does not rot your insides. I hope my mom will leave me alone now"), it would have been a highly-ranked experiment in spite of the crude presentation.

I also agree that learning is the best prize of all, and that parents should be proudest of that rather than any medal or ribbon.