Polly
I never thought my soil was very good - it is full of rocks and clay. Nasturtiums seem to love it and they don't do well in fertile soil. The only thing I really fertilize are my clems and roses.
.
I have always planted bulbs and other plants using bone meal. Not sure if that makes a difference or not as I think of bone meal primarily for root development. The alliums do seem to thrive, though.
One other thing- different types of alliums will flower during different months of the growing season. So, with different varieties, you can get a broad coverage of flowering alliums.