St John’s Wort

Question

Have had St John’s Wort for at least 20 years, but after the first couple of years it’s blooms diminished. We have added Peat to the soil, with limited results. The foliage appears healthy. It is in a mostly sunny spot, and I don’t believe I can move it, although I have transplanted small offshoots.

Answer 1

You may have excess nitrogen in the soil, which will inhibit flowering.
You an feed phosphorous, with Bone Meal.

https://www.gardeningknowhow.com/edible/herbs/st-johns-wort/st-johns-wort-plant-care.htm