Ice melts, leaves emerge and tulips bloom--the winter world comes alive as the earth warms. Scientists have discovered that you can measure the amount of heat it takes to make some spring events occur. This accumulated heat is measured in units called "Growing Degree Days". This activity will help to understand this concept. Measure temperatures each day, and analyze the role temperature plays in setting the pace of spring's arrival.
1. Ask students to think about the steps in baking a cake. The oven must be set at a certain temperature--and the cake must remain in the oven for a certain length of time--in order for it to bake properly. A cake placed in a cold oven won't bake no matter how long it remains there. Ask students how the requirements for baking a cake might be similar to the needs of growing plants. See if they can develop the analogy to explain that it takes a certain amount of heat, accumulated over time, in order for plants to grow.
Also, just as a cake requires a certain temperature for proper baking, there's a threshold temperature at which plants begin to grow. This is called the "base temperature". The base temperature we will use for tulips is 40 degrees F. That is, we only expect tulips to grow on days that the temperature is above 40 degrees F. When it's below 40 degrees F, we don't expect any growth to occur.
2. In order to find out how much heat tulips need to grow and bloom, students will add up the heat received every day--as long as it is warmer than 40 degrees, the base temperature.
3. Print out the following pages and follow the instructions and examples provided: