Attml - If you have a chance to conduct the experiment again, try adding a "Cup D" - decaffeinated coffee. My bet is that it is not the caffein limiting the growth and you would get the same results as the caffeinated cup.
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Originally Posted by attml
I know I am a little late in this thread but saw it and just wanted to put something out there. Be careful how much in the way of coffee grounds you use because they can stunt plant growth (no joke). There has always been studies about caffeine stunting growth in humans, but apparently caffeine can stunt growth in plants as well. In 8th grade science we were asked to do an experiment on 3 plants using the same seeds in 3 separate containers to test the stunting of growth theory in coffee. Cup A got only water, cup B received lightly caffinated tea and cup C got dark heavily caffeinate coffee. All 3 plants received an equal amout of liquid and a equal amount of light. The result of the experiment was pretty cool and very consistant across the class. The cups with water grew the highest, tea grew second highest and the coffee fed plants came in last every time! There was a very noticable difference between the water plant and the coffee plant! The conclusion: Caffinated coffee stunts plant growth!
Just an FYI and if your kids have to do an experiment for science at school for a project and need an idea that is a pretty good one!
Mark
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