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Science Fair Project Help For Students and Parents


Plants are wonderful subjects for science projects.  Here are some hints on how to make your project a success.

Hints for Designing Your Experiment

1) Don’t wait until the last minute. The longer you can run your experiment, the more dramatic your results will be.

2) Start with a theory. This will be the basis of your experiment. A theory might be that different rates of fertilizing plants will result in different heights of plants at the end of the experiment period.

3) When you set up your experiment, remember to only vary one condition. This is called the “variable“. Hold all other conditions the same, or “constant“. This is because if you have two or more things that are changing, you will not know which one is changing your results. For example: if you are testing the effects of different rates of plant food (the variable is the rate of feeding), then everything else should be kept as similar as possible. The amount of water, the amount of light, temperature, the type of plant, and the size of the plants you started with must be the same for all of the plants in the test.

4) You must have something that you are testing against as a benchmark or standard: this is called a “control“.  For instance: if you are testing effects of changing the rate of fertilizer, you could have any of various items as the control. You could say that the control is the group of plants with no fertilizer. Another experimenter might say that the group of plants fertilized at the rate listed on the package is the control. When you finish your experiment, all plants are compared to the control to look for differences.

5) To reduce effects due to random chance, each test group and the control should have several (or more) plants. When you evaluate your experiment, you take the average of the several plants in each group as the result. In the fertilizer test, you might find that the heights of bean plants fed at a certain rate were 10 centimeters (cm), 8 cm, 12 cm, 12 cm and 14 cm. The average is 11.2 cm, which is different than any of your individual results.

6) When you select your plants or seedlings to start your experiment, each individual should be as similar to the next as possible. This is again to reduce the effects of random chance. You should record an initial evaluation of your test groups-color, height, number of leaves…this will give you a starting point to compare changes to. Photos as you go along are also helpful for your report.

7) Be honest.  Sometimes an experiment just doesn’t show anything, or some catastrophe strikes and everything dies.  A scientist reports what she sees, not what she thinks should happen.

Experiments Using Plants Grown from Seeds

1) Seed selection-choose seeds that germinate quickly and with a high rate of germination. Those marked with an asterisk (*) germinate in 3 to 5 days from sowing.

a) Recommended seeds

1. Beans*
2. Peas*
3. Summer squash-zucchini and yellow varieties*
4. Melons-canteloupe and watermelon*
5. Radishes
6. Lawn grass
7. Tomatoes
8. Peppers
9. Zinnias
10. Lettuce-Bibb, Grand Rapids, Simpson and Red Leaf for example

b) Non-Recommended Seeds

These seeds tend to be more variable in germination or require longer times to germinate.

1. Woody plants-trees, shrubs
2. Perennials
3. Most annuals
4. Herbs

2) Propagation, or Germinating and Growing Plants from Seed

The following will help ensure that you get a good set of seedlings to start with.  Also, read the information on the back of the seed package.  It will give you more specific advice.

a) Use freshly packaged seed. As seed ages, some of it will die, reducing your rate of germination.

b) For hard-shelled seeds such as beans, peas, or radishes-soak seeds in lukewarm water for 2 to 3 hours.

c) Plant seeds in moist (but not soggy) potting soil or germinating mix, in a new, clean seeding tray. A clean tray and commercial potting soil will help to reduce the possibility of losing your seedlings to a disease.

d) Plant seeds to the depth recommended on the seed packet. Most seeds should be covered with a light layer of potting soil, ground sphagnum moss or vermiculite. Other seeds must not be covered or they will not germinate. The packet will tell you what to do.

e) Keep soil moist, but not soggy.

f) Most seeds prefer a soil temperature of about 72 degrees Fahrenheit. Cold soil or hot soil may kill the seed.

g) When seed germinates, most seedlings will grow best if placed in a sunny window or about 6 inches from fluorescent lights left on for about 16 hours per day.

h) When the plants have two or 4 leaves, transplant them to small flower pots or peat pots filled with potting soil.  They can be teased out of the germination tray with a pencil without doing too much damage to the roots.  Give them a week to establish before starting your experiment.

i) Keep the seedlings in a sunny window, unless your experiment involves varying light levels.

j) Potting soils often have an initial “charge” or fertilizer that will last a couple of weeks before you need to fertilize with a houseplant fertilizer. Refer to the bag for details.

Experiments Using Established Plants

1. Growth Experiments

In the winter, established plants tend to grow fairly slowly.

a) Recommended

1) Forcing bulbs–such as Paper White Narcissus, Amaryllis.
2) Basil-grows fast but has a tendency to die if in a cool room or if kept too damp.
3) The so-called “Wandering Jew” group of houseplants.

b) Not Recommended

1) Most annuals, houseplants, herbs, perennials or woody plants, because they are dormant or grow too slowly in winter to show much in the way of results.

2. Light, Fertilizer, Soil, Water, and Temperature Experiments

Any available houseplant, herb or annual as long as you can get enough individuals that are similar to one another.

Good luck with your project – Feel free to leave a comment on this article or any other article on our site. We would love to hear your feedback.

By: Larry Hurley

Larry Hurley

Larry Hurley, perennials specialist for Behnke Nurseries (now retired), started with Behnke’s in1984. Larry enjoys travel, food and photography. He and his wife Carolyn have visited Australia, New Zealand, Thailand, Brazil, South Korea and much of Europe. Their home is on a shady lot where a lot of perennials have met their Maker over the years.

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