Gone with the Wind: Plant Seed Dispersal

A science activity from Science Buddies, based on a project from the Botanical Society of America

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Scattering seeds! Learn how some of the most fun seeds of summer travel so well on the breeze. Can you design a seed that scatters well with the wind?

Key conceptsPlantsAerodynamics

Introduction

Background

Seeds are dispersed in several different ways. In some plants seeds are housed within a fruit (such as apples or oranges). These fruits, including the seeds, are eaten by animals who then disperse the seeds when they defecate. Some fruits can be carried by water, such as a floating coconut. Some seeds have little hooks that can stick on to an animal's furry coat. (You may have gotten them stuck on your clothing if you ever went hiking in the woods or tall grass.)

Other seeds are dispersed by the wind—such as the "winged" seeds from a maple tree that spin and "helicopter" through the air as they fall or the light feathery seeds from a dandelion that can catch on the breeze. The longer a seed stays in the air, the farther it can be blown by the wind, helping the plant species widely scatter its offspring. In this project you will make your own artificial "seeds" from craft materials. Can you design seeds that will stay in the air for a long time?

Materials

• Examples of different seeds that are dispersed by the wind (Depending on where you live, you may be able to find some of these seeds outside. If you have access to the Internet, you can also do a Web search for maple seeds, dandelion seeds and other types of wind-dispersed seeds to help get ideas.)
• Small, uniform, lightweight objects that you can use as "seeds" (For example, you could use small paper clips or small binder clips; or purchase a bag of real seeds—such as sunflower seeds—at the supermarket.)
• Craft supplies to build dispersal mechanisms for your seeds (These could be as simple as paper and tape or you could also use things such as streamers, cotton balls or even items you find outside, such as blades of grass.)
• Scissors, tape and glue for cutting and attaching your craft supplies to your seeds (Be careful when using scissors.)
• A window fan or large box fan (Use with caution and appropriate supervision.)
• Stopwatch or timer (optional)
• Measuring tape or ruler (optional)

Preparation

• Clear an open area in the room where you will do the seed-testing activity.
• Place the fan on a table or chair, aimed across the room. You can also do the experiment outside on a windy day.

Procedure

• Design and build several—at least four—dispersal mechanisms for your seeds. The activity works best if you can create at least two similar dispersal mechanisms to test against one another (see examples below). You can use your imagination and come up with your own ideas but here are a few to get you started (using a paper clip as an example "seed"):
  • Attach a paper clip to a small, square piece of paper, about the size of a Sticky Note, without making any changes to the paper.
  • Attach a paper clip to another small piece of paper, but make a several parallel cuts in one side of the paper to give it "frills," and bend them outward.
  • Attach a paper clip to a cotton ball.
  • Attach a paper clip to a cotton ball that you have pulled on to expand it a bit and make it wispier.
  • Cut out some paper in the shape of a maple seed and attach a paper clip.
• Turn on the fan. Standing in the same place, try dropping your seeds one at a time in front of the fan. Also try dropping a plain "seed" (for example, a regular paper clip with nothing attached) to see what happens.
• Think about your results.
• Extra: Have a friend use a stopwatch to time how long it takes the seeds to hit the ground. This might be easier if you drop the seeds from a higher location. (Have a tall adult drop them, carefully stand on a chair or drop them from the top of stairs.)
• Extra: Use a tape measure to record how far the seeds travel horizontally from where you drop them to where they hit the ground.
• Extra:

Observations and results

You should find that adding light materials to the "seed" can make it fall more slowly and blow farther—however, the shape of the materials is also very important. For example, a paper clip attached to a crumpled-up piece of paper will still fall very fast. A piece of paper with a "wing" design (similar to that of a maple seed) or a bunch of individual streamers (like a dandelion seed), however, will fall more slowly and be blown farther by the fan. Exactly how far the seeds blow will depend on the strength of your fan but you should definitely see a difference in the horizontal distance traveled between a "plain" seed and one with a dispersal mechanism. When you take your best designs and try to improve on them, you mimic the process of evolution—because the "best" seed designs in nature are the ones most likely to reproduce!

More to exploreGone With the Wind: An Experiment on Seed and Fruit Dispersal, from Science BuddiesSailing Seeds: An Experiment in Wind Dispersal, original project from the Botanical Society of AmericaMake a Whirlybird from Paper, from Science Activities for All Ages!, from Science Buddies

Science Buddies

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