Use the graph to compare the average height of the plants at the end of Week 3. Which type of plant grew the fastest and is therefore the tallest? ✔ sunflowers Which type of plant grew the slowest and is therefore the shortest? ✔ birch trees Was there a measureable difference in the average height of the plants between the control groups and the experimental groups? ✔ yes What effect does adding nutrients have on the total number and average height of sunflowers and birch trees?