So about a year and a half ago I started Some S. rubra sbsp rubra from seed from the ICPS seed bank, and at about 6 months I fertilized 1 of the 2 pots with osmocote 14-14-14 four month Flower and Vegetable plant food. I placed 5 pellets evenly apart in the pot, about a centimeter deep in the soil. These were the results(cat for scale):
The pot on the left did not receive the fertilizer while the pot on the right did. This is by no means a scientific study as only 2 pots were used, but it clearly shows the difference between fertilized and non-fertilized plants. These plants are right next to each other and everything is the same beside the fertilization.