Not necessarily too fertile to grow, just to grow as it would normally. Fertilize almost anything too much and it will put on a lot of fast green growth and little or no flowers. D. nubigenum is an alpine plant, native to rocky, mineral soils with very little fertility. You may find that it will have trouble wintering over well, partly due to the fertile soil and partly due to wet winters (if you have them). They are very sensitive to winter moisture.
