What's in Miracle-Gro?

In class, we had a question about plant food.  I knew that plants don't need soil to make their own food (all they need is water and sunlight), but I do know that Miracle-Gro makes plants grow bigger and faster than they would otherwise.  So, what's in this stuff?  I thought it might be hormones, but I was wrong!  It's mostly nitrogen, phosphorous, and potassium, with trace amounts of other elements such as iron and copper. 

How do these elements make the plants grow?  Nitrogen helps the process of photosynthesis because it is an essential part of chlorophyll.  Too little of it, and the leaves will turn yellow.  Too much of it, and the plant can experience nitrogen burn and may die.  The trick is to find the happy medium. 

http://www.house-garden.us/articles/the-role-of-nitrogen-in-plants/


Phosphorous helps the plants to convert nutrients in order to grow, and potassium helps plants fight off disease and retain water during a drought.  You can find information about the roles of phosphorous and potassium in plants here:

http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm

http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/plants-potassium.htm

But there is a problem with using Miracle-Gro.  Too much of it can cause plants to become sick and die.  Also, there is the problem of fertilizer runoff.  Since it helps the production of photosynthesis, if it runs off into a water source, it can cause algal blooms in which algae growth experiences a huge increase.  The increased algae in the water requires more oxygen, which depletes the level of breathable oxygen for fish.  This can cause huge populations of fish to die.

What's the answer?  If you just HAVE to use commercial fertilizer, limit the use to whenever your plants aren't thriving and actually need a nutrient boost.  But compost pretty much solves all of these problems.  So, make a compost pile in your backyard, and use it!  Throw banana peels in for potassium, and you've got the perfect solution.  It's better for the soil, the plants, and the environment, as a whole.

These petunias are a good example:  The one on the right was grown in compost, while the one on the left was grown with Miracle-Gro.  In this case, the compost was even better!

Photo was taken here:  http://qualitygreenspecialists.com/index.php?p=1_16_Premium-blend-Compost

You can teach about plants and nutrients with a simple experiment in your class.  You could do this with outside plants or indoor potted ones.  Just make sure they are the same species and have the same access to sunlight and water.  Make one the control (no fertilizer and use only potting soil and water), put commercial fertilizer on one, and on the last, use organic compost, and record the growth and health of each plant over a period of two months.  During the lessons, discuss the process of photosynthesis, and allow the students to predict which plant will do the best and why. 

 And don't forget to put earthworms in your compost pile or bin!