Let's start with the problem. I have two greenhouses set at different temperatures. I also planted greens on different dates throughout the fall. In the chart above you can see:
- The average temperatures were different in the two greenhouses, especially as it got cooler
- The temperatures vary depending what time of the season greens are planted
"Growing degree units are a measure of heat accumulation used by horticulturists, gardeners, and farmers to predict plant and pest development rates such as the date that a flower will bloom or a crop reach maturity." WikipediaSo, they measure heat accumulation. Luckily they are easy to calculate, you just need to know:
- Average daily temperature
- The base temperature, below which your plants won't grow. For salad greens I use 40 degrees F. This is called the biofix.
Growing degree units are used to predict flowering blooming, crop maturity or insect emergence. I've been using them to examine the growth rate data, but more on that in the future